diff --git a/modules/openapi-generator/src/main/resources/csharp-netcore/HttpSigningConfiguration.mustache b/modules/openapi-generator/src/main/resources/csharp-netcore/HttpSigningConfiguration.mustache
index 6b773b8d596..a1169150ea2 100644
--- a/modules/openapi-generator/src/main/resources/csharp-netcore/HttpSigningConfiguration.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp-netcore/HttpSigningConfiguration.mustache
@@ -40,6 +40,11 @@ namespace {{packageName}}.Client
         /// </summary>
         public string KeyFilePath { get; set; }
 
+        /// <summary>
+        /// Specify the API key in the form of a string, either configure the KeyString property or configure the KeyFilePath property.
+        /// </summary>
+        public string KeyString { get; set; }
+
         /// <summary>
         /// Gets the key pass phrase for password protected key
         /// </summary>
@@ -104,6 +109,17 @@ namespace {{packageName}}.Client
             //the list of signed headers and a base64-encoded signature.
             const string HEADER_AUTHORIZATION = "Authorization";
 
+            //Read the api key from the file
+            if(string.IsNullOrEmpty(this.KeyString))
+            {
+                this.KeyString = ReadApiKeyFromFile(KeyFilePath);
+            }
+
+            if(string.IsNullOrEmpty(KeyString))
+            {
+                throw new Exception("No API key has been provided.");
+            }
+
             //Hash table to store singed headers
             var HttpSignedRequestHeader = new Dictionary<string, string>();
             var HttpSignatureHeader = new Dictionary<string, string>();
@@ -242,7 +258,7 @@ namespace {{packageName}}.Client
             var headerValuesString = string.Join("\n", headerValuesList);
             var signatureStringHash = GetStringHash(HashAlgorithm.ToString(), headerValuesString);
             string headerSignatureStr = null;
-            var keyType = GetKeyType(KeyFilePath);
+            var keyType = GetKeyType(KeyString);
 
             if (keyType == PrivateKeyType.RSA)
             {
@@ -293,7 +309,7 @@ namespace {{packageName}}.Client
 
         private string GetRSASignature(byte[] stringToSign)
         {
-            RSA rsa = GetRSAProviderFromPemFile(KeyFilePath, KeyPassPhrase);
+            RSA rsa = GetRSAProviderFromPemFile(KeyString, KeyPassPhrase);
             if (SigningAlgorithm == "RSASSA-PSS")
             {
                 var signedbytes = rsa.SignHash(stringToSign, HashAlgorithm, RSASignaturePadding.Pss);
@@ -317,16 +333,7 @@ namespace {{packageName}}.Client
         /// <returns>ECDSA signature</returns>
         private string GetECDSASignature(byte[] dataToSign)
         {
-            string keyStr = string.Empty;
-            if (File.Exists(KeyFilePath))
-            {
-                keyStr = File.ReadAllText(KeyFilePath);
-            }
-            else
-            {
-                keyStr = KeyFilePath;
-            }
-
+            var keyStr = KeyString;
             const string ecKeyHeader = "-----BEGIN EC PRIVATE KEY-----";
             const string ecKeyFooter = "-----END EC PRIVATE KEY-----";
             var ecKeyBase64String = keyStr.Replace(ecKeyHeader, "").Replace(ecKeyFooter, "").Trim();
@@ -419,22 +426,13 @@ namespace {{packageName}}.Client
             return derBytes.ToArray();
         }
 
-        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string pemfile, SecureString keyPassPhrase = null)
+        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string keyString, SecureString keyPassPhrase = null)
         {
             const string pempubheader = "-----BEGIN PUBLIC KEY-----";
             const string pempubfooter = "-----END PUBLIC KEY-----";
             bool isPrivateKeyFile = true;
             byte[] pemkey = null;
-
-            string pemstr = string.Empty;
-            if (File.Exists(pemfile))
-            {
-                pemstr = File.ReadAllText(pemfile).Trim();
-            }
-            else
-            {
-                pemstr = pemfile;
-            }
+            string pemstr = keyString;
 
             if (pemstr.StartsWith(pempubheader) && pemstr.EndsWith(pempubfooter))
             {
@@ -721,20 +719,15 @@ namespace {{packageName}}.Client
         /// <summary>
         /// Detect the key type from the pem file.
         /// </summary>
-        /// <param name="keyFilePath">key file path in pem format</param>
+        /// <param name="keyString">api key in string format</param>
         /// <returns>Private Key Type</returns>
-        private PrivateKeyType GetKeyType(string keyFilePath)
+        private PrivateKeyType GetKeyType(string keyString)
         {
             string[] key = null;
 
-            if (File.Exists(keyFilePath))
+            if (string.IsNullOrEmpty(keyString))
             {
-                key = File.ReadAllLines(keyFilePath);
-            }
-            else
-            {
-                // The ApiKeyFilePath is passed as string
-                key = new string[] { keyFilePath };
+                throw new Exception("No API key has been provided.");
             }
 
             const string ecPrivateKeyHeader = "BEGIN EC PRIVATE KEY";
@@ -744,6 +737,7 @@ namespace {{packageName}}.Client
             //var pkcs8Header = "BEGIN PRIVATE KEY";
             //var pkcs8Footer = "END PRIVATE KEY";
             PrivateKeyType keyType;
+            key = KeyString.TrimEnd().Split('\n');
 
             if (key[0].Contains(rsaPrivateKeyHeader) &&
                 key[key.Length - 1].ToString().Contains(rsaPrivateFooter))
@@ -761,6 +755,25 @@ namespace {{packageName}}.Client
             }
             return keyType;
         }
+
+        /// <summary>
+        /// Read the api key form the api key file path and stored it in KeyString property.
+        /// </summary>
+        /// <param name="apiKeyFilePath">api key file path</param>
+        private string ReadApiKeyFromFile(string apiKeyFilePath)
+        {
+            string apiKeyString = null;
+            
+            if(File.Exists(apiKeyFilePath))
+            {
+                apiKeyString = File.ReadAllText(apiKeyFilePath);
+            }
+            else
+            {
+                throw new Exception("Provided API key file path does not exists.");
+            }
+            return apiKeyString;
+        }
         #endregion
     }
 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-ConditionalSerialization/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-ConditionalSerialization/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 0b3e867d0f4..05442e501a9 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-ConditionalSerialization/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-ConditionalSerialization/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -48,6 +48,11 @@ namespace Org.OpenAPITools.Client
         /// </summary>
         public string KeyFilePath { get; set; }
 
+        /// <summary>
+        /// Specify the API key in the form of a string, either configure the KeyString property or configure the KeyFilePath property.
+        /// </summary>
+        public string KeyString { get; set; }
+
         /// <summary>
         /// Gets the key pass phrase for password protected key
         /// </summary>
@@ -112,6 +117,17 @@ namespace Org.OpenAPITools.Client
             //the list of signed headers and a base64-encoded signature.
             const string HEADER_AUTHORIZATION = "Authorization";
 
+            //Read the api key from the file
+            if(string.IsNullOrEmpty(this.KeyString))
+            {
+                this.KeyString = ReadApiKeyFromFile(KeyFilePath);
+            }
+
+            if(string.IsNullOrEmpty(KeyString))
+            {
+                throw new Exception("No API key has been provided.");
+            }
+
             //Hash table to store singed headers
             var HttpSignedRequestHeader = new Dictionary<string, string>();
             var HttpSignatureHeader = new Dictionary<string, string>();
@@ -250,7 +266,7 @@ namespace Org.OpenAPITools.Client
             var headerValuesString = string.Join("\n", headerValuesList);
             var signatureStringHash = GetStringHash(HashAlgorithm.ToString(), headerValuesString);
             string headerSignatureStr = null;
-            var keyType = GetKeyType(KeyFilePath);
+            var keyType = GetKeyType(KeyString);
 
             if (keyType == PrivateKeyType.RSA)
             {
@@ -301,7 +317,7 @@ namespace Org.OpenAPITools.Client
 
         private string GetRSASignature(byte[] stringToSign)
         {
-            RSA rsa = GetRSAProviderFromPemFile(KeyFilePath, KeyPassPhrase);
+            RSA rsa = GetRSAProviderFromPemFile(KeyString, KeyPassPhrase);
             if (SigningAlgorithm == "RSASSA-PSS")
             {
                 var signedbytes = rsa.SignHash(stringToSign, HashAlgorithm, RSASignaturePadding.Pss);
@@ -325,16 +341,7 @@ namespace Org.OpenAPITools.Client
         /// <returns>ECDSA signature</returns>
         private string GetECDSASignature(byte[] dataToSign)
         {
-            string keyStr = string.Empty;
-            if (File.Exists(KeyFilePath))
-            {
-                keyStr = File.ReadAllText(KeyFilePath);
-            }
-            else
-            {
-                keyStr = KeyFilePath;
-            }
-
+            var keyStr = KeyString;
             const string ecKeyHeader = "-----BEGIN EC PRIVATE KEY-----";
             const string ecKeyFooter = "-----END EC PRIVATE KEY-----";
             var ecKeyBase64String = keyStr.Replace(ecKeyHeader, "").Replace(ecKeyFooter, "").Trim();
@@ -427,22 +434,13 @@ namespace Org.OpenAPITools.Client
             return derBytes.ToArray();
         }
 
-        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string pemfile, SecureString keyPassPhrase = null)
+        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string keyString, SecureString keyPassPhrase = null)
         {
             const string pempubheader = "-----BEGIN PUBLIC KEY-----";
             const string pempubfooter = "-----END PUBLIC KEY-----";
             bool isPrivateKeyFile = true;
             byte[] pemkey = null;
-
-            string pemstr = string.Empty;
-            if (File.Exists(pemfile))
-            {
-                pemstr = File.ReadAllText(pemfile).Trim();
-            }
-            else
-            {
-                pemstr = pemfile;
-            }
+            string pemstr = keyString;
 
             if (pemstr.StartsWith(pempubheader) && pemstr.EndsWith(pempubfooter))
             {
@@ -729,20 +727,15 @@ namespace Org.OpenAPITools.Client
         /// <summary>
         /// Detect the key type from the pem file.
         /// </summary>
-        /// <param name="keyFilePath">key file path in pem format</param>
+        /// <param name="keyString">api key in string format</param>
         /// <returns>Private Key Type</returns>
-        private PrivateKeyType GetKeyType(string keyFilePath)
+        private PrivateKeyType GetKeyType(string keyString)
         {
             string[] key = null;
 
-            if (File.Exists(keyFilePath))
+            if (string.IsNullOrEmpty(keyString))
             {
-                key = File.ReadAllLines(keyFilePath);
-            }
-            else
-            {
-                // The ApiKeyFilePath is passed as string
-                key = new string[] { keyFilePath };
+                throw new Exception("No API key has been provided.");
             }
 
             const string ecPrivateKeyHeader = "BEGIN EC PRIVATE KEY";
@@ -752,6 +745,7 @@ namespace Org.OpenAPITools.Client
             //var pkcs8Header = "BEGIN PRIVATE KEY";
             //var pkcs8Footer = "END PRIVATE KEY";
             PrivateKeyType keyType;
+            key = KeyString.TrimEnd().Split('\n');
 
             if (key[0].Contains(rsaPrivateKeyHeader) &&
                 key[key.Length - 1].ToString().Contains(rsaPrivateFooter))
@@ -769,6 +763,25 @@ namespace Org.OpenAPITools.Client
             }
             return keyType;
         }
+
+        /// <summary>
+        /// Read the api key form the api key file path and stored it in KeyString property.
+        /// </summary>
+        /// <param name="apiKeyFilePath">api key file path</param>
+        private string ReadApiKeyFromFile(string apiKeyFilePath)
+        {
+            string apiKeyString = null;
+            
+            if(File.Exists(apiKeyFilePath))
+            {
+                apiKeyString = File.ReadAllText(apiKeyFilePath);
+            }
+            else
+            {
+                throw new Exception("Provided API key file path does not exists.");
+            }
+            return apiKeyString;
+        }
         #endregion
     }
 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 0b3e867d0f4..05442e501a9 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -48,6 +48,11 @@ namespace Org.OpenAPITools.Client
         /// </summary>
         public string KeyFilePath { get; set; }
 
+        /// <summary>
+        /// Specify the API key in the form of a string, either configure the KeyString property or configure the KeyFilePath property.
+        /// </summary>
+        public string KeyString { get; set; }
+
         /// <summary>
         /// Gets the key pass phrase for password protected key
         /// </summary>
@@ -112,6 +117,17 @@ namespace Org.OpenAPITools.Client
             //the list of signed headers and a base64-encoded signature.
             const string HEADER_AUTHORIZATION = "Authorization";
 
+            //Read the api key from the file
+            if(string.IsNullOrEmpty(this.KeyString))
+            {
+                this.KeyString = ReadApiKeyFromFile(KeyFilePath);
+            }
+
+            if(string.IsNullOrEmpty(KeyString))
+            {
+                throw new Exception("No API key has been provided.");
+            }
+
             //Hash table to store singed headers
             var HttpSignedRequestHeader = new Dictionary<string, string>();
             var HttpSignatureHeader = new Dictionary<string, string>();
@@ -250,7 +266,7 @@ namespace Org.OpenAPITools.Client
             var headerValuesString = string.Join("\n", headerValuesList);
             var signatureStringHash = GetStringHash(HashAlgorithm.ToString(), headerValuesString);
             string headerSignatureStr = null;
-            var keyType = GetKeyType(KeyFilePath);
+            var keyType = GetKeyType(KeyString);
 
             if (keyType == PrivateKeyType.RSA)
             {
@@ -301,7 +317,7 @@ namespace Org.OpenAPITools.Client
 
         private string GetRSASignature(byte[] stringToSign)
         {
-            RSA rsa = GetRSAProviderFromPemFile(KeyFilePath, KeyPassPhrase);
+            RSA rsa = GetRSAProviderFromPemFile(KeyString, KeyPassPhrase);
             if (SigningAlgorithm == "RSASSA-PSS")
             {
                 var signedbytes = rsa.SignHash(stringToSign, HashAlgorithm, RSASignaturePadding.Pss);
@@ -325,16 +341,7 @@ namespace Org.OpenAPITools.Client
         /// <returns>ECDSA signature</returns>
         private string GetECDSASignature(byte[] dataToSign)
         {
-            string keyStr = string.Empty;
-            if (File.Exists(KeyFilePath))
-            {
-                keyStr = File.ReadAllText(KeyFilePath);
-            }
-            else
-            {
-                keyStr = KeyFilePath;
-            }
-
+            var keyStr = KeyString;
             const string ecKeyHeader = "-----BEGIN EC PRIVATE KEY-----";
             const string ecKeyFooter = "-----END EC PRIVATE KEY-----";
             var ecKeyBase64String = keyStr.Replace(ecKeyHeader, "").Replace(ecKeyFooter, "").Trim();
@@ -427,22 +434,13 @@ namespace Org.OpenAPITools.Client
             return derBytes.ToArray();
         }
 
-        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string pemfile, SecureString keyPassPhrase = null)
+        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string keyString, SecureString keyPassPhrase = null)
         {
             const string pempubheader = "-----BEGIN PUBLIC KEY-----";
             const string pempubfooter = "-----END PUBLIC KEY-----";
             bool isPrivateKeyFile = true;
             byte[] pemkey = null;
-
-            string pemstr = string.Empty;
-            if (File.Exists(pemfile))
-            {
-                pemstr = File.ReadAllText(pemfile).Trim();
-            }
-            else
-            {
-                pemstr = pemfile;
-            }
+            string pemstr = keyString;
 
             if (pemstr.StartsWith(pempubheader) && pemstr.EndsWith(pempubfooter))
             {
@@ -729,20 +727,15 @@ namespace Org.OpenAPITools.Client
         /// <summary>
         /// Detect the key type from the pem file.
         /// </summary>
-        /// <param name="keyFilePath">key file path in pem format</param>
+        /// <param name="keyString">api key in string format</param>
         /// <returns>Private Key Type</returns>
-        private PrivateKeyType GetKeyType(string keyFilePath)
+        private PrivateKeyType GetKeyType(string keyString)
         {
             string[] key = null;
 
-            if (File.Exists(keyFilePath))
+            if (string.IsNullOrEmpty(keyString))
             {
-                key = File.ReadAllLines(keyFilePath);
-            }
-            else
-            {
-                // The ApiKeyFilePath is passed as string
-                key = new string[] { keyFilePath };
+                throw new Exception("No API key has been provided.");
             }
 
             const string ecPrivateKeyHeader = "BEGIN EC PRIVATE KEY";
@@ -752,6 +745,7 @@ namespace Org.OpenAPITools.Client
             //var pkcs8Header = "BEGIN PRIVATE KEY";
             //var pkcs8Footer = "END PRIVATE KEY";
             PrivateKeyType keyType;
+            key = KeyString.TrimEnd().Split('\n');
 
             if (key[0].Contains(rsaPrivateKeyHeader) &&
                 key[key.Length - 1].ToString().Contains(rsaPrivateFooter))
@@ -769,6 +763,25 @@ namespace Org.OpenAPITools.Client
             }
             return keyType;
         }
+
+        /// <summary>
+        /// Read the api key form the api key file path and stored it in KeyString property.
+        /// </summary>
+        /// <param name="apiKeyFilePath">api key file path</param>
+        private string ReadApiKeyFromFile(string apiKeyFilePath)
+        {
+            string apiKeyString = null;
+            
+            if(File.Exists(apiKeyFilePath))
+            {
+                apiKeyString = File.ReadAllText(apiKeyFilePath);
+            }
+            else
+            {
+                throw new Exception("Provided API key file path does not exists.");
+            }
+            return apiKeyString;
+        }
         #endregion
     }
 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 0b3e867d0f4..05442e501a9 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -48,6 +48,11 @@ namespace Org.OpenAPITools.Client
         /// </summary>
         public string KeyFilePath { get; set; }
 
+        /// <summary>
+        /// Specify the API key in the form of a string, either configure the KeyString property or configure the KeyFilePath property.
+        /// </summary>
+        public string KeyString { get; set; }
+
         /// <summary>
         /// Gets the key pass phrase for password protected key
         /// </summary>
@@ -112,6 +117,17 @@ namespace Org.OpenAPITools.Client
             //the list of signed headers and a base64-encoded signature.
             const string HEADER_AUTHORIZATION = "Authorization";
 
+            //Read the api key from the file
+            if(string.IsNullOrEmpty(this.KeyString))
+            {
+                this.KeyString = ReadApiKeyFromFile(KeyFilePath);
+            }
+
+            if(string.IsNullOrEmpty(KeyString))
+            {
+                throw new Exception("No API key has been provided.");
+            }
+
             //Hash table to store singed headers
             var HttpSignedRequestHeader = new Dictionary<string, string>();
             var HttpSignatureHeader = new Dictionary<string, string>();
@@ -250,7 +266,7 @@ namespace Org.OpenAPITools.Client
             var headerValuesString = string.Join("\n", headerValuesList);
             var signatureStringHash = GetStringHash(HashAlgorithm.ToString(), headerValuesString);
             string headerSignatureStr = null;
-            var keyType = GetKeyType(KeyFilePath);
+            var keyType = GetKeyType(KeyString);
 
             if (keyType == PrivateKeyType.RSA)
             {
@@ -301,7 +317,7 @@ namespace Org.OpenAPITools.Client
 
         private string GetRSASignature(byte[] stringToSign)
         {
-            RSA rsa = GetRSAProviderFromPemFile(KeyFilePath, KeyPassPhrase);
+            RSA rsa = GetRSAProviderFromPemFile(KeyString, KeyPassPhrase);
             if (SigningAlgorithm == "RSASSA-PSS")
             {
                 var signedbytes = rsa.SignHash(stringToSign, HashAlgorithm, RSASignaturePadding.Pss);
@@ -325,16 +341,7 @@ namespace Org.OpenAPITools.Client
         /// <returns>ECDSA signature</returns>
         private string GetECDSASignature(byte[] dataToSign)
         {
-            string keyStr = string.Empty;
-            if (File.Exists(KeyFilePath))
-            {
-                keyStr = File.ReadAllText(KeyFilePath);
-            }
-            else
-            {
-                keyStr = KeyFilePath;
-            }
-
+            var keyStr = KeyString;
             const string ecKeyHeader = "-----BEGIN EC PRIVATE KEY-----";
             const string ecKeyFooter = "-----END EC PRIVATE KEY-----";
             var ecKeyBase64String = keyStr.Replace(ecKeyHeader, "").Replace(ecKeyFooter, "").Trim();
@@ -427,22 +434,13 @@ namespace Org.OpenAPITools.Client
             return derBytes.ToArray();
         }
 
-        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string pemfile, SecureString keyPassPhrase = null)
+        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string keyString, SecureString keyPassPhrase = null)
         {
             const string pempubheader = "-----BEGIN PUBLIC KEY-----";
             const string pempubfooter = "-----END PUBLIC KEY-----";
             bool isPrivateKeyFile = true;
             byte[] pemkey = null;
-
-            string pemstr = string.Empty;
-            if (File.Exists(pemfile))
-            {
-                pemstr = File.ReadAllText(pemfile).Trim();
-            }
-            else
-            {
-                pemstr = pemfile;
-            }
+            string pemstr = keyString;
 
             if (pemstr.StartsWith(pempubheader) && pemstr.EndsWith(pempubfooter))
             {
@@ -729,20 +727,15 @@ namespace Org.OpenAPITools.Client
         /// <summary>
         /// Detect the key type from the pem file.
         /// </summary>
-        /// <param name="keyFilePath">key file path in pem format</param>
+        /// <param name="keyString">api key in string format</param>
         /// <returns>Private Key Type</returns>
-        private PrivateKeyType GetKeyType(string keyFilePath)
+        private PrivateKeyType GetKeyType(string keyString)
         {
             string[] key = null;
 
-            if (File.Exists(keyFilePath))
+            if (string.IsNullOrEmpty(keyString))
             {
-                key = File.ReadAllLines(keyFilePath);
-            }
-            else
-            {
-                // The ApiKeyFilePath is passed as string
-                key = new string[] { keyFilePath };
+                throw new Exception("No API key has been provided.");
             }
 
             const string ecPrivateKeyHeader = "BEGIN EC PRIVATE KEY";
@@ -752,6 +745,7 @@ namespace Org.OpenAPITools.Client
             //var pkcs8Header = "BEGIN PRIVATE KEY";
             //var pkcs8Footer = "END PRIVATE KEY";
             PrivateKeyType keyType;
+            key = KeyString.TrimEnd().Split('\n');
 
             if (key[0].Contains(rsaPrivateKeyHeader) &&
                 key[key.Length - 1].ToString().Contains(rsaPrivateFooter))
@@ -769,6 +763,25 @@ namespace Org.OpenAPITools.Client
             }
             return keyType;
         }
+
+        /// <summary>
+        /// Read the api key form the api key file path and stored it in KeyString property.
+        /// </summary>
+        /// <param name="apiKeyFilePath">api key file path</param>
+        private string ReadApiKeyFromFile(string apiKeyFilePath)
+        {
+            string apiKeyString = null;
+            
+            if(File.Exists(apiKeyFilePath))
+            {
+                apiKeyString = File.ReadAllText(apiKeyFilePath);
+            }
+            else
+            {
+                throw new Exception("Provided API key file path does not exists.");
+            }
+            return apiKeyString;
+        }
         #endregion
     }
 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net48/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-net48/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 0b3e867d0f4..05442e501a9 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net48/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net48/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -48,6 +48,11 @@ namespace Org.OpenAPITools.Client
         /// </summary>
         public string KeyFilePath { get; set; }
 
+        /// <summary>
+        /// Specify the API key in the form of a string, either configure the KeyString property or configure the KeyFilePath property.
+        /// </summary>
+        public string KeyString { get; set; }
+
         /// <summary>
         /// Gets the key pass phrase for password protected key
         /// </summary>
@@ -112,6 +117,17 @@ namespace Org.OpenAPITools.Client
             //the list of signed headers and a base64-encoded signature.
             const string HEADER_AUTHORIZATION = "Authorization";
 
+            //Read the api key from the file
+            if(string.IsNullOrEmpty(this.KeyString))
+            {
+                this.KeyString = ReadApiKeyFromFile(KeyFilePath);
+            }
+
+            if(string.IsNullOrEmpty(KeyString))
+            {
+                throw new Exception("No API key has been provided.");
+            }
+
             //Hash table to store singed headers
             var HttpSignedRequestHeader = new Dictionary<string, string>();
             var HttpSignatureHeader = new Dictionary<string, string>();
@@ -250,7 +266,7 @@ namespace Org.OpenAPITools.Client
             var headerValuesString = string.Join("\n", headerValuesList);
             var signatureStringHash = GetStringHash(HashAlgorithm.ToString(), headerValuesString);
             string headerSignatureStr = null;
-            var keyType = GetKeyType(KeyFilePath);
+            var keyType = GetKeyType(KeyString);
 
             if (keyType == PrivateKeyType.RSA)
             {
@@ -301,7 +317,7 @@ namespace Org.OpenAPITools.Client
 
         private string GetRSASignature(byte[] stringToSign)
         {
-            RSA rsa = GetRSAProviderFromPemFile(KeyFilePath, KeyPassPhrase);
+            RSA rsa = GetRSAProviderFromPemFile(KeyString, KeyPassPhrase);
             if (SigningAlgorithm == "RSASSA-PSS")
             {
                 var signedbytes = rsa.SignHash(stringToSign, HashAlgorithm, RSASignaturePadding.Pss);
@@ -325,16 +341,7 @@ namespace Org.OpenAPITools.Client
         /// <returns>ECDSA signature</returns>
         private string GetECDSASignature(byte[] dataToSign)
         {
-            string keyStr = string.Empty;
-            if (File.Exists(KeyFilePath))
-            {
-                keyStr = File.ReadAllText(KeyFilePath);
-            }
-            else
-            {
-                keyStr = KeyFilePath;
-            }
-
+            var keyStr = KeyString;
             const string ecKeyHeader = "-----BEGIN EC PRIVATE KEY-----";
             const string ecKeyFooter = "-----END EC PRIVATE KEY-----";
             var ecKeyBase64String = keyStr.Replace(ecKeyHeader, "").Replace(ecKeyFooter, "").Trim();
@@ -427,22 +434,13 @@ namespace Org.OpenAPITools.Client
             return derBytes.ToArray();
         }
 
-        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string pemfile, SecureString keyPassPhrase = null)
+        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string keyString, SecureString keyPassPhrase = null)
         {
             const string pempubheader = "-----BEGIN PUBLIC KEY-----";
             const string pempubfooter = "-----END PUBLIC KEY-----";
             bool isPrivateKeyFile = true;
             byte[] pemkey = null;
-
-            string pemstr = string.Empty;
-            if (File.Exists(pemfile))
-            {
-                pemstr = File.ReadAllText(pemfile).Trim();
-            }
-            else
-            {
-                pemstr = pemfile;
-            }
+            string pemstr = keyString;
 
             if (pemstr.StartsWith(pempubheader) && pemstr.EndsWith(pempubfooter))
             {
@@ -729,20 +727,15 @@ namespace Org.OpenAPITools.Client
         /// <summary>
         /// Detect the key type from the pem file.
         /// </summary>
-        /// <param name="keyFilePath">key file path in pem format</param>
+        /// <param name="keyString">api key in string format</param>
         /// <returns>Private Key Type</returns>
-        private PrivateKeyType GetKeyType(string keyFilePath)
+        private PrivateKeyType GetKeyType(string keyString)
         {
             string[] key = null;
 
-            if (File.Exists(keyFilePath))
+            if (string.IsNullOrEmpty(keyString))
             {
-                key = File.ReadAllLines(keyFilePath);
-            }
-            else
-            {
-                // The ApiKeyFilePath is passed as string
-                key = new string[] { keyFilePath };
+                throw new Exception("No API key has been provided.");
             }
 
             const string ecPrivateKeyHeader = "BEGIN EC PRIVATE KEY";
@@ -752,6 +745,7 @@ namespace Org.OpenAPITools.Client
             //var pkcs8Header = "BEGIN PRIVATE KEY";
             //var pkcs8Footer = "END PRIVATE KEY";
             PrivateKeyType keyType;
+            key = KeyString.TrimEnd().Split('\n');
 
             if (key[0].Contains(rsaPrivateKeyHeader) &&
                 key[key.Length - 1].ToString().Contains(rsaPrivateFooter))
@@ -769,6 +763,25 @@ namespace Org.OpenAPITools.Client
             }
             return keyType;
         }
+
+        /// <summary>
+        /// Read the api key form the api key file path and stored it in KeyString property.
+        /// </summary>
+        /// <param name="apiKeyFilePath">api key file path</param>
+        private string ReadApiKeyFromFile(string apiKeyFilePath)
+        {
+            string apiKeyString = null;
+            
+            if(File.Exists(apiKeyFilePath))
+            {
+                apiKeyString = File.ReadAllText(apiKeyFilePath);
+            }
+            else
+            {
+                throw new Exception("Provided API key file path does not exists.");
+            }
+            return apiKeyString;
+        }
         #endregion
     }
 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 0b3e867d0f4..05442e501a9 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -48,6 +48,11 @@ namespace Org.OpenAPITools.Client
         /// </summary>
         public string KeyFilePath { get; set; }
 
+        /// <summary>
+        /// Specify the API key in the form of a string, either configure the KeyString property or configure the KeyFilePath property.
+        /// </summary>
+        public string KeyString { get; set; }
+
         /// <summary>
         /// Gets the key pass phrase for password protected key
         /// </summary>
@@ -112,6 +117,17 @@ namespace Org.OpenAPITools.Client
             //the list of signed headers and a base64-encoded signature.
             const string HEADER_AUTHORIZATION = "Authorization";
 
+            //Read the api key from the file
+            if(string.IsNullOrEmpty(this.KeyString))
+            {
+                this.KeyString = ReadApiKeyFromFile(KeyFilePath);
+            }
+
+            if(string.IsNullOrEmpty(KeyString))
+            {
+                throw new Exception("No API key has been provided.");
+            }
+
             //Hash table to store singed headers
             var HttpSignedRequestHeader = new Dictionary<string, string>();
             var HttpSignatureHeader = new Dictionary<string, string>();
@@ -250,7 +266,7 @@ namespace Org.OpenAPITools.Client
             var headerValuesString = string.Join("\n", headerValuesList);
             var signatureStringHash = GetStringHash(HashAlgorithm.ToString(), headerValuesString);
             string headerSignatureStr = null;
-            var keyType = GetKeyType(KeyFilePath);
+            var keyType = GetKeyType(KeyString);
 
             if (keyType == PrivateKeyType.RSA)
             {
@@ -301,7 +317,7 @@ namespace Org.OpenAPITools.Client
 
         private string GetRSASignature(byte[] stringToSign)
         {
-            RSA rsa = GetRSAProviderFromPemFile(KeyFilePath, KeyPassPhrase);
+            RSA rsa = GetRSAProviderFromPemFile(KeyString, KeyPassPhrase);
             if (SigningAlgorithm == "RSASSA-PSS")
             {
                 var signedbytes = rsa.SignHash(stringToSign, HashAlgorithm, RSASignaturePadding.Pss);
@@ -325,16 +341,7 @@ namespace Org.OpenAPITools.Client
         /// <returns>ECDSA signature</returns>
         private string GetECDSASignature(byte[] dataToSign)
         {
-            string keyStr = string.Empty;
-            if (File.Exists(KeyFilePath))
-            {
-                keyStr = File.ReadAllText(KeyFilePath);
-            }
-            else
-            {
-                keyStr = KeyFilePath;
-            }
-
+            var keyStr = KeyString;
             const string ecKeyHeader = "-----BEGIN EC PRIVATE KEY-----";
             const string ecKeyFooter = "-----END EC PRIVATE KEY-----";
             var ecKeyBase64String = keyStr.Replace(ecKeyHeader, "").Replace(ecKeyFooter, "").Trim();
@@ -427,22 +434,13 @@ namespace Org.OpenAPITools.Client
             return derBytes.ToArray();
         }
 
-        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string pemfile, SecureString keyPassPhrase = null)
+        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string keyString, SecureString keyPassPhrase = null)
         {
             const string pempubheader = "-----BEGIN PUBLIC KEY-----";
             const string pempubfooter = "-----END PUBLIC KEY-----";
             bool isPrivateKeyFile = true;
             byte[] pemkey = null;
-
-            string pemstr = string.Empty;
-            if (File.Exists(pemfile))
-            {
-                pemstr = File.ReadAllText(pemfile).Trim();
-            }
-            else
-            {
-                pemstr = pemfile;
-            }
+            string pemstr = keyString;
 
             if (pemstr.StartsWith(pempubheader) && pemstr.EndsWith(pempubfooter))
             {
@@ -729,20 +727,15 @@ namespace Org.OpenAPITools.Client
         /// <summary>
         /// Detect the key type from the pem file.
         /// </summary>
-        /// <param name="keyFilePath">key file path in pem format</param>
+        /// <param name="keyString">api key in string format</param>
         /// <returns>Private Key Type</returns>
-        private PrivateKeyType GetKeyType(string keyFilePath)
+        private PrivateKeyType GetKeyType(string keyString)
         {
             string[] key = null;
 
-            if (File.Exists(keyFilePath))
+            if (string.IsNullOrEmpty(keyString))
             {
-                key = File.ReadAllLines(keyFilePath);
-            }
-            else
-            {
-                // The ApiKeyFilePath is passed as string
-                key = new string[] { keyFilePath };
+                throw new Exception("No API key has been provided.");
             }
 
             const string ecPrivateKeyHeader = "BEGIN EC PRIVATE KEY";
@@ -752,6 +745,7 @@ namespace Org.OpenAPITools.Client
             //var pkcs8Header = "BEGIN PRIVATE KEY";
             //var pkcs8Footer = "END PRIVATE KEY";
             PrivateKeyType keyType;
+            key = KeyString.TrimEnd().Split('\n');
 
             if (key[0].Contains(rsaPrivateKeyHeader) &&
                 key[key.Length - 1].ToString().Contains(rsaPrivateFooter))
@@ -769,6 +763,25 @@ namespace Org.OpenAPITools.Client
             }
             return keyType;
         }
+
+        /// <summary>
+        /// Read the api key form the api key file path and stored it in KeyString property.
+        /// </summary>
+        /// <param name="apiKeyFilePath">api key file path</param>
+        private string ReadApiKeyFromFile(string apiKeyFilePath)
+        {
+            string apiKeyString = null;
+            
+            if(File.Exists(apiKeyFilePath))
+            {
+                apiKeyString = File.ReadAllText(apiKeyFilePath);
+            }
+            else
+            {
+                throw new Exception("Provided API key file path does not exists.");
+            }
+            return apiKeyString;
+        }
         #endregion
     }
 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-unityWebRequest/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-unityWebRequest/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 0b3e867d0f4..05442e501a9 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-unityWebRequest/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-unityWebRequest/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -48,6 +48,11 @@ namespace Org.OpenAPITools.Client
         /// </summary>
         public string KeyFilePath { get; set; }
 
+        /// <summary>
+        /// Specify the API key in the form of a string, either configure the KeyString property or configure the KeyFilePath property.
+        /// </summary>
+        public string KeyString { get; set; }
+
         /// <summary>
         /// Gets the key pass phrase for password protected key
         /// </summary>
@@ -112,6 +117,17 @@ namespace Org.OpenAPITools.Client
             //the list of signed headers and a base64-encoded signature.
             const string HEADER_AUTHORIZATION = "Authorization";
 
+            //Read the api key from the file
+            if(string.IsNullOrEmpty(this.KeyString))
+            {
+                this.KeyString = ReadApiKeyFromFile(KeyFilePath);
+            }
+
+            if(string.IsNullOrEmpty(KeyString))
+            {
+                throw new Exception("No API key has been provided.");
+            }
+
             //Hash table to store singed headers
             var HttpSignedRequestHeader = new Dictionary<string, string>();
             var HttpSignatureHeader = new Dictionary<string, string>();
@@ -250,7 +266,7 @@ namespace Org.OpenAPITools.Client
             var headerValuesString = string.Join("\n", headerValuesList);
             var signatureStringHash = GetStringHash(HashAlgorithm.ToString(), headerValuesString);
             string headerSignatureStr = null;
-            var keyType = GetKeyType(KeyFilePath);
+            var keyType = GetKeyType(KeyString);
 
             if (keyType == PrivateKeyType.RSA)
             {
@@ -301,7 +317,7 @@ namespace Org.OpenAPITools.Client
 
         private string GetRSASignature(byte[] stringToSign)
         {
-            RSA rsa = GetRSAProviderFromPemFile(KeyFilePath, KeyPassPhrase);
+            RSA rsa = GetRSAProviderFromPemFile(KeyString, KeyPassPhrase);
             if (SigningAlgorithm == "RSASSA-PSS")
             {
                 var signedbytes = rsa.SignHash(stringToSign, HashAlgorithm, RSASignaturePadding.Pss);
@@ -325,16 +341,7 @@ namespace Org.OpenAPITools.Client
         /// <returns>ECDSA signature</returns>
         private string GetECDSASignature(byte[] dataToSign)
         {
-            string keyStr = string.Empty;
-            if (File.Exists(KeyFilePath))
-            {
-                keyStr = File.ReadAllText(KeyFilePath);
-            }
-            else
-            {
-                keyStr = KeyFilePath;
-            }
-
+            var keyStr = KeyString;
             const string ecKeyHeader = "-----BEGIN EC PRIVATE KEY-----";
             const string ecKeyFooter = "-----END EC PRIVATE KEY-----";
             var ecKeyBase64String = keyStr.Replace(ecKeyHeader, "").Replace(ecKeyFooter, "").Trim();
@@ -427,22 +434,13 @@ namespace Org.OpenAPITools.Client
             return derBytes.ToArray();
         }
 
-        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string pemfile, SecureString keyPassPhrase = null)
+        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string keyString, SecureString keyPassPhrase = null)
         {
             const string pempubheader = "-----BEGIN PUBLIC KEY-----";
             const string pempubfooter = "-----END PUBLIC KEY-----";
             bool isPrivateKeyFile = true;
             byte[] pemkey = null;
-
-            string pemstr = string.Empty;
-            if (File.Exists(pemfile))
-            {
-                pemstr = File.ReadAllText(pemfile).Trim();
-            }
-            else
-            {
-                pemstr = pemfile;
-            }
+            string pemstr = keyString;
 
             if (pemstr.StartsWith(pempubheader) && pemstr.EndsWith(pempubfooter))
             {
@@ -729,20 +727,15 @@ namespace Org.OpenAPITools.Client
         /// <summary>
         /// Detect the key type from the pem file.
         /// </summary>
-        /// <param name="keyFilePath">key file path in pem format</param>
+        /// <param name="keyString">api key in string format</param>
         /// <returns>Private Key Type</returns>
-        private PrivateKeyType GetKeyType(string keyFilePath)
+        private PrivateKeyType GetKeyType(string keyString)
         {
             string[] key = null;
 
-            if (File.Exists(keyFilePath))
+            if (string.IsNullOrEmpty(keyString))
             {
-                key = File.ReadAllLines(keyFilePath);
-            }
-            else
-            {
-                // The ApiKeyFilePath is passed as string
-                key = new string[] { keyFilePath };
+                throw new Exception("No API key has been provided.");
             }
 
             const string ecPrivateKeyHeader = "BEGIN EC PRIVATE KEY";
@@ -752,6 +745,7 @@ namespace Org.OpenAPITools.Client
             //var pkcs8Header = "BEGIN PRIVATE KEY";
             //var pkcs8Footer = "END PRIVATE KEY";
             PrivateKeyType keyType;
+            key = KeyString.TrimEnd().Split('\n');
 
             if (key[0].Contains(rsaPrivateKeyHeader) &&
                 key[key.Length - 1].ToString().Contains(rsaPrivateFooter))
@@ -769,6 +763,25 @@ namespace Org.OpenAPITools.Client
             }
             return keyType;
         }
+
+        /// <summary>
+        /// Read the api key form the api key file path and stored it in KeyString property.
+        /// </summary>
+        /// <param name="apiKeyFilePath">api key file path</param>
+        private string ReadApiKeyFromFile(string apiKeyFilePath)
+        {
+            string apiKeyString = null;
+            
+            if(File.Exists(apiKeyFilePath))
+            {
+                apiKeyString = File.ReadAllText(apiKeyFilePath);
+            }
+            else
+            {
+                throw new Exception("Provided API key file path does not exists.");
+            }
+            return apiKeyString;
+        }
         #endregion
     }
 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 0b3e867d0f4..05442e501a9 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -48,6 +48,11 @@ namespace Org.OpenAPITools.Client
         /// </summary>
         public string KeyFilePath { get; set; }
 
+        /// <summary>
+        /// Specify the API key in the form of a string, either configure the KeyString property or configure the KeyFilePath property.
+        /// </summary>
+        public string KeyString { get; set; }
+
         /// <summary>
         /// Gets the key pass phrase for password protected key
         /// </summary>
@@ -112,6 +117,17 @@ namespace Org.OpenAPITools.Client
             //the list of signed headers and a base64-encoded signature.
             const string HEADER_AUTHORIZATION = "Authorization";
 
+            //Read the api key from the file
+            if(string.IsNullOrEmpty(this.KeyString))
+            {
+                this.KeyString = ReadApiKeyFromFile(KeyFilePath);
+            }
+
+            if(string.IsNullOrEmpty(KeyString))
+            {
+                throw new Exception("No API key has been provided.");
+            }
+
             //Hash table to store singed headers
             var HttpSignedRequestHeader = new Dictionary<string, string>();
             var HttpSignatureHeader = new Dictionary<string, string>();
@@ -250,7 +266,7 @@ namespace Org.OpenAPITools.Client
             var headerValuesString = string.Join("\n", headerValuesList);
             var signatureStringHash = GetStringHash(HashAlgorithm.ToString(), headerValuesString);
             string headerSignatureStr = null;
-            var keyType = GetKeyType(KeyFilePath);
+            var keyType = GetKeyType(KeyString);
 
             if (keyType == PrivateKeyType.RSA)
             {
@@ -301,7 +317,7 @@ namespace Org.OpenAPITools.Client
 
         private string GetRSASignature(byte[] stringToSign)
         {
-            RSA rsa = GetRSAProviderFromPemFile(KeyFilePath, KeyPassPhrase);
+            RSA rsa = GetRSAProviderFromPemFile(KeyString, KeyPassPhrase);
             if (SigningAlgorithm == "RSASSA-PSS")
             {
                 var signedbytes = rsa.SignHash(stringToSign, HashAlgorithm, RSASignaturePadding.Pss);
@@ -325,16 +341,7 @@ namespace Org.OpenAPITools.Client
         /// <returns>ECDSA signature</returns>
         private string GetECDSASignature(byte[] dataToSign)
         {
-            string keyStr = string.Empty;
-            if (File.Exists(KeyFilePath))
-            {
-                keyStr = File.ReadAllText(KeyFilePath);
-            }
-            else
-            {
-                keyStr = KeyFilePath;
-            }
-
+            var keyStr = KeyString;
             const string ecKeyHeader = "-----BEGIN EC PRIVATE KEY-----";
             const string ecKeyFooter = "-----END EC PRIVATE KEY-----";
             var ecKeyBase64String = keyStr.Replace(ecKeyHeader, "").Replace(ecKeyFooter, "").Trim();
@@ -427,22 +434,13 @@ namespace Org.OpenAPITools.Client
             return derBytes.ToArray();
         }
 
-        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string pemfile, SecureString keyPassPhrase = null)
+        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string keyString, SecureString keyPassPhrase = null)
         {
             const string pempubheader = "-----BEGIN PUBLIC KEY-----";
             const string pempubfooter = "-----END PUBLIC KEY-----";
             bool isPrivateKeyFile = true;
             byte[] pemkey = null;
-
-            string pemstr = string.Empty;
-            if (File.Exists(pemfile))
-            {
-                pemstr = File.ReadAllText(pemfile).Trim();
-            }
-            else
-            {
-                pemstr = pemfile;
-            }
+            string pemstr = keyString;
 
             if (pemstr.StartsWith(pempubheader) && pemstr.EndsWith(pempubfooter))
             {
@@ -729,20 +727,15 @@ namespace Org.OpenAPITools.Client
         /// <summary>
         /// Detect the key type from the pem file.
         /// </summary>
-        /// <param name="keyFilePath">key file path in pem format</param>
+        /// <param name="keyString">api key in string format</param>
         /// <returns>Private Key Type</returns>
-        private PrivateKeyType GetKeyType(string keyFilePath)
+        private PrivateKeyType GetKeyType(string keyString)
         {
             string[] key = null;
 
-            if (File.Exists(keyFilePath))
+            if (string.IsNullOrEmpty(keyString))
             {
-                key = File.ReadAllLines(keyFilePath);
-            }
-            else
-            {
-                // The ApiKeyFilePath is passed as string
-                key = new string[] { keyFilePath };
+                throw new Exception("No API key has been provided.");
             }
 
             const string ecPrivateKeyHeader = "BEGIN EC PRIVATE KEY";
@@ -752,6 +745,7 @@ namespace Org.OpenAPITools.Client
             //var pkcs8Header = "BEGIN PRIVATE KEY";
             //var pkcs8Footer = "END PRIVATE KEY";
             PrivateKeyType keyType;
+            key = KeyString.TrimEnd().Split('\n');
 
             if (key[0].Contains(rsaPrivateKeyHeader) &&
                 key[key.Length - 1].ToString().Contains(rsaPrivateFooter))
@@ -769,6 +763,25 @@ namespace Org.OpenAPITools.Client
             }
             return keyType;
         }
+
+        /// <summary>
+        /// Read the api key form the api key file path and stored it in KeyString property.
+        /// </summary>
+        /// <param name="apiKeyFilePath">api key file path</param>
+        private string ReadApiKeyFromFile(string apiKeyFilePath)
+        {
+            string apiKeyString = null;
+            
+            if(File.Exists(apiKeyFilePath))
+            {
+                apiKeyString = File.ReadAllText(apiKeyFilePath);
+            }
+            else
+            {
+                throw new Exception("Provided API key file path does not exists.");
+            }
+            return apiKeyString;
+        }
         #endregion
     }
 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 0b3e867d0f4..05442e501a9 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -48,6 +48,11 @@ namespace Org.OpenAPITools.Client
         /// </summary>
         public string KeyFilePath { get; set; }
 
+        /// <summary>
+        /// Specify the API key in the form of a string, either configure the KeyString property or configure the KeyFilePath property.
+        /// </summary>
+        public string KeyString { get; set; }
+
         /// <summary>
         /// Gets the key pass phrase for password protected key
         /// </summary>
@@ -112,6 +117,17 @@ namespace Org.OpenAPITools.Client
             //the list of signed headers and a base64-encoded signature.
             const string HEADER_AUTHORIZATION = "Authorization";
 
+            //Read the api key from the file
+            if(string.IsNullOrEmpty(this.KeyString))
+            {
+                this.KeyString = ReadApiKeyFromFile(KeyFilePath);
+            }
+
+            if(string.IsNullOrEmpty(KeyString))
+            {
+                throw new Exception("No API key has been provided.");
+            }
+
             //Hash table to store singed headers
             var HttpSignedRequestHeader = new Dictionary<string, string>();
             var HttpSignatureHeader = new Dictionary<string, string>();
@@ -250,7 +266,7 @@ namespace Org.OpenAPITools.Client
             var headerValuesString = string.Join("\n", headerValuesList);
             var signatureStringHash = GetStringHash(HashAlgorithm.ToString(), headerValuesString);
             string headerSignatureStr = null;
-            var keyType = GetKeyType(KeyFilePath);
+            var keyType = GetKeyType(KeyString);
 
             if (keyType == PrivateKeyType.RSA)
             {
@@ -301,7 +317,7 @@ namespace Org.OpenAPITools.Client
 
         private string GetRSASignature(byte[] stringToSign)
         {
-            RSA rsa = GetRSAProviderFromPemFile(KeyFilePath, KeyPassPhrase);
+            RSA rsa = GetRSAProviderFromPemFile(KeyString, KeyPassPhrase);
             if (SigningAlgorithm == "RSASSA-PSS")
             {
                 var signedbytes = rsa.SignHash(stringToSign, HashAlgorithm, RSASignaturePadding.Pss);
@@ -325,16 +341,7 @@ namespace Org.OpenAPITools.Client
         /// <returns>ECDSA signature</returns>
         private string GetECDSASignature(byte[] dataToSign)
         {
-            string keyStr = string.Empty;
-            if (File.Exists(KeyFilePath))
-            {
-                keyStr = File.ReadAllText(KeyFilePath);
-            }
-            else
-            {
-                keyStr = KeyFilePath;
-            }
-
+            var keyStr = KeyString;
             const string ecKeyHeader = "-----BEGIN EC PRIVATE KEY-----";
             const string ecKeyFooter = "-----END EC PRIVATE KEY-----";
             var ecKeyBase64String = keyStr.Replace(ecKeyHeader, "").Replace(ecKeyFooter, "").Trim();
@@ -427,22 +434,13 @@ namespace Org.OpenAPITools.Client
             return derBytes.ToArray();
         }
 
-        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string pemfile, SecureString keyPassPhrase = null)
+        private  RSACryptoServiceProvider GetRSAProviderFromPemFile(string keyString, SecureString keyPassPhrase = null)
         {
             const string pempubheader = "-----BEGIN PUBLIC KEY-----";
             const string pempubfooter = "-----END PUBLIC KEY-----";
             bool isPrivateKeyFile = true;
             byte[] pemkey = null;
-
-            string pemstr = string.Empty;
-            if (File.Exists(pemfile))
-            {
-                pemstr = File.ReadAllText(pemfile).Trim();
-            }
-            else
-            {
-                pemstr = pemfile;
-            }
+            string pemstr = keyString;
 
             if (pemstr.StartsWith(pempubheader) && pemstr.EndsWith(pempubfooter))
             {
@@ -729,20 +727,15 @@ namespace Org.OpenAPITools.Client
         /// <summary>
         /// Detect the key type from the pem file.
         /// </summary>
-        /// <param name="keyFilePath">key file path in pem format</param>
+        /// <param name="keyString">api key in string format</param>
         /// <returns>Private Key Type</returns>
-        private PrivateKeyType GetKeyType(string keyFilePath)
+        private PrivateKeyType GetKeyType(string keyString)
         {
             string[] key = null;
 
-            if (File.Exists(keyFilePath))
+            if (string.IsNullOrEmpty(keyString))
             {
-                key = File.ReadAllLines(keyFilePath);
-            }
-            else
-            {
-                // The ApiKeyFilePath is passed as string
-                key = new string[] { keyFilePath };
+                throw new Exception("No API key has been provided.");
             }
 
             const string ecPrivateKeyHeader = "BEGIN EC PRIVATE KEY";
@@ -752,6 +745,7 @@ namespace Org.OpenAPITools.Client
             //var pkcs8Header = "BEGIN PRIVATE KEY";
             //var pkcs8Footer = "END PRIVATE KEY";
             PrivateKeyType keyType;
+            key = KeyString.TrimEnd().Split('\n');
 
             if (key[0].Contains(rsaPrivateKeyHeader) &&
                 key[key.Length - 1].ToString().Contains(rsaPrivateFooter))
@@ -769,6 +763,25 @@ namespace Org.OpenAPITools.Client
             }
             return keyType;
         }
+
+        /// <summary>
+        /// Read the api key form the api key file path and stored it in KeyString property.
+        /// </summary>
+        /// <param name="apiKeyFilePath">api key file path</param>
+        private string ReadApiKeyFromFile(string apiKeyFilePath)
+        {
+            string apiKeyString = null;
+            
+            if(File.Exists(apiKeyFilePath))
+            {
+                apiKeyString = File.ReadAllText(apiKeyFilePath);
+            }
+            else
+            {
+                throw new Exception("Provided API key file path does not exists.");
+            }
+            return apiKeyString;
+        }
         #endregion
     }
 }