diff --git a/modules/openapi-generator/src/main/resources/csharp-netcore/ApiClient.mustache b/modules/openapi-generator/src/main/resources/csharp-netcore/ApiClient.mustache
index f3232ec5f16..55b3e96c4c7 100644
--- a/modules/openapi-generator/src/main/resources/csharp-netcore/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp-netcore/ApiClient.mustache
@@ -270,6 +270,14 @@ namespace {{packageName}}.Client
                 }
             }
 
+            if (configuration.DefaultHeaders != null)
+            {
+                foreach (var headerParam in configuration.DefaultHeaders)
+                {
+                    request.AddHeader(headerParam.Key, headerParam.Value);
+                }
+            }
+
             if (options.HeaderParameters != null)
             {
                 foreach (var headerParam in options.HeaderParameters)
diff --git a/modules/openapi-generator/src/main/resources/csharp-netcore/Configuration.mustache b/modules/openapi-generator/src/main/resources/csharp-netcore/Configuration.mustache
index 7f70ee4c5e6..f9a29c90aa3 100644
--- a/modules/openapi-generator/src/main/resources/csharp-netcore/Configuration.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp-netcore/Configuration.mustache
@@ -35,7 +35,7 @@ namespace {{packageName}}.Client
         #endregion Constants
 
         #region Static Members
-        
+
         /// <summary>
         /// Default creation of exceptions for a given method name and response object
         /// </summary>
@@ -65,7 +65,7 @@ namespace {{packageName}}.Client
         /// Example: http://localhost:3000/v1/
         /// </summary>
         private String _basePath;
-        
+
         /// <summary>
         /// Gets or sets the API key based on the authentication name.
         /// This is the key and value comprising the "secret" for acessing an API.
@@ -94,7 +94,7 @@ namespace {{packageName}}.Client
         {
             UserAgent = "{{#httpUserAgent}}{{.}}{{/httpUserAgent}}{{^httpUserAgent}}OpenAPI-Generator/{{packageVersion}}/csharp{{/httpUserAgent}}";
             BasePath = "{{{basePath}}}";
-            DefaultHeader = new {{^net35}}Concurrent{{/net35}}Dictionary<string, string>();
+            DefaultHeaders = new {{^net35}}Concurrent{{/net35}}Dictionary<string, string>();
             ApiKey = new {{^net35}}Concurrent{{/net35}}Dictionary<string, string>();
             ApiKeyPrefix = new {{^net35}}Concurrent{{/net35}}Dictionary<string, string>();
 
@@ -107,15 +107,15 @@ namespace {{packageName}}.Client
         /// </summary>
         [System.Diagnostics.CodeAnalysis.SuppressMessage("ReSharper", "VirtualMemberCallInConstructor")]
         public Configuration(
-            IDictionary<string, string> defaultHeader,
+            IDictionary<string, string> defaultHeaders,
             IDictionary<string, string> apiKey,
             IDictionary<string, string> apiKeyPrefix,
             string basePath = "{{{basePath}}}") : this()
         {
             if (string.{{^net35}}IsNullOrWhiteSpace{{/net35}}{{#net35}}IsNullOrEmpty{{/net35}}(basePath))
                 throw new ArgumentException("The provided basePath is invalid.", "basePath");
-            if (defaultHeader == null)
-                throw new ArgumentNullException("defaultHeader");
+            if (defaultHeaders == null)
+                throw new ArgumentNullException("defaultHeaders");
             if (apiKey == null)
                 throw new ArgumentNullException("apiKey");
             if (apiKeyPrefix == null)
@@ -123,9 +123,9 @@ namespace {{packageName}}.Client
 
             BasePath = basePath;
 
-            foreach (var keyValuePair in defaultHeader)
+            foreach (var keyValuePair in defaultHeaders)
             {
-                DefaultHeader.Add(keyValuePair);
+                DefaultHeaders.Add(keyValuePair);
             }
 
             foreach (var keyValuePair in apiKey)
@@ -156,7 +156,23 @@ namespace {{packageName}}.Client
         /// <summary>
         /// Gets or sets the default header.
         /// </summary>
-        public virtual IDictionary<string, string> DefaultHeader { get; set; }
+        [Obsolete("Use DefaultHeaders instead.")]
+        public virtual IDictionary<string, string> DefaultHeader
+        {
+            get
+            {
+                return DefaultHeaders;
+            }
+            set
+            {
+                DefaultHeaders = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the default headers.
+        /// </summary>
+        public virtual IDictionary<string, string> DefaultHeaders { get; set; }
 
         /// <summary>
         /// Gets or sets the HTTP timeout (milliseconds) of ApiClient. Default to 100000 milliseconds.
@@ -374,17 +390,17 @@ namespace {{packageName}}.Client
             
             Dictionary<string, string> apiKey = first.ApiKey.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
             Dictionary<string, string> apiKeyPrefix = first.ApiKeyPrefix.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
-            Dictionary<string, string> defaultHeader = first.DefaultHeader.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
+            Dictionary<string, string> defaultHeaders = first.DefaultHeaders.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
             
             foreach (var kvp in second.ApiKey) apiKey[kvp.Key] = kvp.Value;
             foreach (var kvp in second.ApiKeyPrefix) apiKeyPrefix[kvp.Key] = kvp.Value;
-            foreach (var kvp in second.DefaultHeader) defaultHeader[kvp.Key] = kvp.Value;
+            foreach (var kvp in second.DefaultHeaders) defaultHeaders[kvp.Key] = kvp.Value;
 
             var config = new Configuration
             {
                 ApiKey = apiKey,
                 ApiKeyPrefix = apiKeyPrefix,
-                DefaultHeader = defaultHeader,
+                DefaultHeader = defaultHeaders,
                 BasePath = second.BasePath ?? first.BasePath,
                 Timeout = second.Timeout,
                 UserAgent = second.UserAgent ?? first.UserAgent,
diff --git a/modules/openapi-generator/src/main/resources/csharp-netcore/IReadableConfiguration.mustache b/modules/openapi-generator/src/main/resources/csharp-netcore/IReadableConfiguration.mustache
index ce165e0c81d..0acef255d6c 100644
--- a/modules/openapi-generator/src/main/resources/csharp-netcore/IReadableConfiguration.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp-netcore/IReadableConfiguration.mustache
@@ -1,5 +1,6 @@
 {{>partial_header}}
 
+using System;
 using System.Collections.Generic;
 
 namespace {{packageName}}.Client
@@ -43,8 +44,15 @@ namespace {{packageName}}.Client
         /// Gets the default header.
         /// </summary>
         /// <value>Default header.</value>
+        [Obsolete("Use DefaultHeaders instead.")]
         IDictionary<string, string> DefaultHeader { get; }
 
+        /// <summary>
+        /// Gets the default headers.
+        /// </summary>
+        /// <value>Default headers.</value>
+        IDictionary<string, string> DefaultHeaders { get; }
+
         /// <summary>
         /// Gets the temp folder path.
         /// </summary>
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/ApiClient.cs
index cb5dc1a6bca..af5165ee251 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -273,6 +273,14 @@ namespace Org.OpenAPITools.Client
                 }
             }
 
+            if (configuration.DefaultHeaders != null)
+            {
+                foreach (var headerParam in configuration.DefaultHeaders)
+                {
+                    request.AddHeader(headerParam.Key, headerParam.Value);
+                }
+            }
+
             if (options.HeaderParameters != null)
             {
                 foreach (var headerParam in options.HeaderParameters)
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/Configuration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/Configuration.cs
index 520e1420265..9fadf1712f3 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/Configuration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/Configuration.cs
@@ -42,7 +42,7 @@ namespace Org.OpenAPITools.Client
         #endregion Constants
 
         #region Static Members
-        
+
         /// <summary>
         /// Default creation of exceptions for a given method name and response object
         /// </summary>
@@ -68,7 +68,7 @@ namespace Org.OpenAPITools.Client
         /// Example: http://localhost:3000/v1/
         /// </summary>
         private String _basePath;
-        
+
         /// <summary>
         /// Gets or sets the API key based on the authentication name.
         /// This is the key and value comprising the "secret" for acessing an API.
@@ -97,7 +97,7 @@ namespace Org.OpenAPITools.Client
         {
             UserAgent = "OpenAPI-Generator/1.0.0/csharp";
             BasePath = "http://petstore.swagger.io:80/v2";
-            DefaultHeader = new ConcurrentDictionary<string, string>();
+            DefaultHeaders = new ConcurrentDictionary<string, string>();
             ApiKey = new ConcurrentDictionary<string, string>();
             ApiKeyPrefix = new ConcurrentDictionary<string, string>();
 
@@ -110,15 +110,15 @@ namespace Org.OpenAPITools.Client
         /// </summary>
         [System.Diagnostics.CodeAnalysis.SuppressMessage("ReSharper", "VirtualMemberCallInConstructor")]
         public Configuration(
-            IDictionary<string, string> defaultHeader,
+            IDictionary<string, string> defaultHeaders,
             IDictionary<string, string> apiKey,
             IDictionary<string, string> apiKeyPrefix,
             string basePath = "http://petstore.swagger.io:80/v2") : this()
         {
             if (string.IsNullOrWhiteSpace(basePath))
                 throw new ArgumentException("The provided basePath is invalid.", "basePath");
-            if (defaultHeader == null)
-                throw new ArgumentNullException("defaultHeader");
+            if (defaultHeaders == null)
+                throw new ArgumentNullException("defaultHeaders");
             if (apiKey == null)
                 throw new ArgumentNullException("apiKey");
             if (apiKeyPrefix == null)
@@ -126,9 +126,9 @@ namespace Org.OpenAPITools.Client
 
             BasePath = basePath;
 
-            foreach (var keyValuePair in defaultHeader)
+            foreach (var keyValuePair in defaultHeaders)
             {
-                DefaultHeader.Add(keyValuePair);
+                DefaultHeaders.Add(keyValuePair);
             }
 
             foreach (var keyValuePair in apiKey)
@@ -159,7 +159,23 @@ namespace Org.OpenAPITools.Client
         /// <summary>
         /// Gets or sets the default header.
         /// </summary>
-        public virtual IDictionary<string, string> DefaultHeader { get; set; }
+        [Obsolete("Use DefaultHeaders instead.")]
+        public virtual IDictionary<string, string> DefaultHeader
+        {
+            get
+            {
+                return DefaultHeaders;
+            }
+            set
+            {
+                DefaultHeaders = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the default headers.
+        /// </summary>
+        public virtual IDictionary<string, string> DefaultHeaders { get; set; }
 
         /// <summary>
         /// Gets or sets the HTTP timeout (milliseconds) of ApiClient. Default to 100000 milliseconds.
@@ -369,17 +385,17 @@ namespace Org.OpenAPITools.Client
             
             Dictionary<string, string> apiKey = first.ApiKey.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
             Dictionary<string, string> apiKeyPrefix = first.ApiKeyPrefix.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
-            Dictionary<string, string> defaultHeader = first.DefaultHeader.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
+            Dictionary<string, string> defaultHeaders = first.DefaultHeaders.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
             
             foreach (var kvp in second.ApiKey) apiKey[kvp.Key] = kvp.Value;
             foreach (var kvp in second.ApiKeyPrefix) apiKeyPrefix[kvp.Key] = kvp.Value;
-            foreach (var kvp in second.DefaultHeader) defaultHeader[kvp.Key] = kvp.Value;
+            foreach (var kvp in second.DefaultHeaders) defaultHeaders[kvp.Key] = kvp.Value;
 
             var config = new Configuration
             {
                 ApiKey = apiKey,
                 ApiKeyPrefix = apiKeyPrefix,
-                DefaultHeader = defaultHeader,
+                DefaultHeader = defaultHeaders,
                 BasePath = second.BasePath ?? first.BasePath,
                 Timeout = second.Timeout,
                 UserAgent = second.UserAgent ?? first.UserAgent,
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/IReadableConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/IReadableConfiguration.cs
index 23e1a0c2e19..8faa7f57838 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/IReadableConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/IReadableConfiguration.cs
@@ -9,6 +9,7 @@
  */
 
 
+using System;
 using System.Collections.Generic;
 
 namespace Org.OpenAPITools.Client
@@ -52,8 +53,15 @@ namespace Org.OpenAPITools.Client
         /// Gets the default header.
         /// </summary>
         /// <value>Default header.</value>
+        [Obsolete("Use DefaultHeaders instead.")]
         IDictionary<string, string> DefaultHeader { get; }
 
+        /// <summary>
+        /// Gets the default headers.
+        /// </summary>
+        /// <value>Default headers.</value>
+        IDictionary<string, string> DefaultHeaders { get; }
+
         /// <summary>
         /// Gets the temp folder path.
         /// </summary>
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/ApiClient.cs b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/ApiClient.cs
index e3db56be21b..05c50bceac0 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/ApiClient.cs
@@ -274,6 +274,14 @@ namespace Org.OpenAPITools.Client
                 }
             }
 
+            if (configuration.DefaultHeaders != null)
+            {
+                foreach (var headerParam in configuration.DefaultHeaders)
+                {
+                    request.AddHeader(headerParam.Key, headerParam.Value);
+                }
+            }
+
             if (options.HeaderParameters != null)
             {
                 foreach (var headerParam in options.HeaderParameters)
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/Configuration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/Configuration.cs
index 25010fbef9e..4317d59a939 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/Configuration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/Configuration.cs
@@ -42,7 +42,7 @@ namespace Org.OpenAPITools.Client
         #endregion Constants
 
         #region Static Members
-        
+
         /// <summary>
         /// Default creation of exceptions for a given method name and response object
         /// </summary>
@@ -72,7 +72,7 @@ namespace Org.OpenAPITools.Client
         /// Example: http://localhost:3000/v1/
         /// </summary>
         private String _basePath;
-        
+
         /// <summary>
         /// Gets or sets the API key based on the authentication name.
         /// This is the key and value comprising the "secret" for acessing an API.
@@ -101,7 +101,7 @@ namespace Org.OpenAPITools.Client
         {
             UserAgent = "OpenAPI-Generator/1.0.0/csharp";
             BasePath = "http://petstore.swagger.io:80/v2";
-            DefaultHeader = new ConcurrentDictionary<string, string>();
+            DefaultHeaders = new ConcurrentDictionary<string, string>();
             ApiKey = new ConcurrentDictionary<string, string>();
             ApiKeyPrefix = new ConcurrentDictionary<string, string>();
 
@@ -114,15 +114,15 @@ namespace Org.OpenAPITools.Client
         /// </summary>
         [System.Diagnostics.CodeAnalysis.SuppressMessage("ReSharper", "VirtualMemberCallInConstructor")]
         public Configuration(
-            IDictionary<string, string> defaultHeader,
+            IDictionary<string, string> defaultHeaders,
             IDictionary<string, string> apiKey,
             IDictionary<string, string> apiKeyPrefix,
             string basePath = "http://petstore.swagger.io:80/v2") : this()
         {
             if (string.IsNullOrWhiteSpace(basePath))
                 throw new ArgumentException("The provided basePath is invalid.", "basePath");
-            if (defaultHeader == null)
-                throw new ArgumentNullException("defaultHeader");
+            if (defaultHeaders == null)
+                throw new ArgumentNullException("defaultHeaders");
             if (apiKey == null)
                 throw new ArgumentNullException("apiKey");
             if (apiKeyPrefix == null)
@@ -130,9 +130,9 @@ namespace Org.OpenAPITools.Client
 
             BasePath = basePath;
 
-            foreach (var keyValuePair in defaultHeader)
+            foreach (var keyValuePair in defaultHeaders)
             {
-                DefaultHeader.Add(keyValuePair);
+                DefaultHeaders.Add(keyValuePair);
             }
 
             foreach (var keyValuePair in apiKey)
@@ -163,7 +163,23 @@ namespace Org.OpenAPITools.Client
         /// <summary>
         /// Gets or sets the default header.
         /// </summary>
-        public virtual IDictionary<string, string> DefaultHeader { get; set; }
+        [Obsolete("Use DefaultHeaders instead.")]
+        public virtual IDictionary<string, string> DefaultHeader
+        {
+            get
+            {
+                return DefaultHeaders;
+            }
+            set
+            {
+                DefaultHeaders = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the default headers.
+        /// </summary>
+        public virtual IDictionary<string, string> DefaultHeaders { get; set; }
 
         /// <summary>
         /// Gets or sets the HTTP timeout (milliseconds) of ApiClient. Default to 100000 milliseconds.
@@ -374,17 +390,17 @@ namespace Org.OpenAPITools.Client
             
             Dictionary<string, string> apiKey = first.ApiKey.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
             Dictionary<string, string> apiKeyPrefix = first.ApiKeyPrefix.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
-            Dictionary<string, string> defaultHeader = first.DefaultHeader.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
+            Dictionary<string, string> defaultHeaders = first.DefaultHeaders.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
             
             foreach (var kvp in second.ApiKey) apiKey[kvp.Key] = kvp.Value;
             foreach (var kvp in second.ApiKeyPrefix) apiKeyPrefix[kvp.Key] = kvp.Value;
-            foreach (var kvp in second.DefaultHeader) defaultHeader[kvp.Key] = kvp.Value;
+            foreach (var kvp in second.DefaultHeaders) defaultHeaders[kvp.Key] = kvp.Value;
 
             var config = new Configuration
             {
                 ApiKey = apiKey,
                 ApiKeyPrefix = apiKeyPrefix,
-                DefaultHeader = defaultHeader,
+                DefaultHeader = defaultHeaders,
                 BasePath = second.BasePath ?? first.BasePath,
                 Timeout = second.Timeout,
                 UserAgent = second.UserAgent ?? first.UserAgent,
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/IReadableConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/IReadableConfiguration.cs
index 23e1a0c2e19..8faa7f57838 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/IReadableConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/IReadableConfiguration.cs
@@ -9,6 +9,7 @@
  */
 
 
+using System;
 using System.Collections.Generic;
 
 namespace Org.OpenAPITools.Client
@@ -52,8 +53,15 @@ namespace Org.OpenAPITools.Client
         /// Gets the default header.
         /// </summary>
         /// <value>Default header.</value>
+        [Obsolete("Use DefaultHeaders instead.")]
         IDictionary<string, string> DefaultHeader { get; }
 
+        /// <summary>
+        /// Gets the default headers.
+        /// </summary>
+        /// <value>Default headers.</value>
+        IDictionary<string, string> DefaultHeaders { get; }
+
         /// <summary>
         /// Gets the temp folder path.
         /// </summary>