diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
index 0bcdbb3a372..68c9344fe36 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
@@ -399,7 +399,7 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen implements Co
                 // check to see if model name is same as the property name
                 // which will result in compilation error
                 // if found, prepend with _ to workaround the limitation
-                if (var.name.equalsIgnoreCase(cm.name)) {
+                if (var.name.equalsIgnoreCase(cm.classname)) {
                     var.name = "_" + var.name;
                 }
             }
diff --git a/modules/openapi-generator/src/test/resources/3_0/java/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml b/modules/openapi-generator/src/test/resources/3_0/java/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml
index 843298825ab..05b1c7abd35 100644
--- a/modules/openapi-generator/src/test/resources/3_0/java/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml
+++ b/modules/openapi-generator/src/test/resources/3_0/java/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml
@@ -1793,6 +1793,8 @@ components:
         '$special[property.name]':
           type: integer
           format: int64
+        '_special_model.name_':
+          type: string
       xml:
         name: '$special[model.name]'
     HealthCheckResult:
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/docs/ModelClient.md b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/docs/ModelClient.md
index 8a1bd169a2f..c29a6287433 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/docs/ModelClient.md
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/docs/ModelClient.md
@@ -4,7 +4,7 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**__Client** | **string** |  | [optional] 
+**_Client** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/docs/SpecialModelName.md b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/docs/SpecialModelName.md
index a27e685165a..648179799e1 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/docs/SpecialModelName.md
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/docs/SpecialModelName.md
@@ -5,6 +5,7 @@
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
 **SpecialPropertyName** | **long** |  | [optional] 
+**_SpecialModelName** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Model/ModelClient.cs
index 16f1dc95bab..4ee431a9b2f 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -38,15 +38,15 @@ namespace Org.OpenAPITools.Model
         /// <param name="_client">_client.</param>
         public ModelClient(string _client = default(string))
         {
-            this.__Client = _client;
+            this._Client = _client;
             this.AdditionalProperties = new Dictionary<string, object>();
         }
 
         /// <summary>
-        /// Gets or Sets __Client
+        /// Gets or Sets _Client
         /// </summary>
         [DataMember(Name = "client", EmitDefaultValue = false)]
-        public string __Client { get; set; }
+        public string _Client { get; set; }
 
         /// <summary>
         /// Gets or Sets additional properties
@@ -62,7 +62,7 @@ namespace Org.OpenAPITools.Model
         {
             var sb = new StringBuilder();
             sb.Append("class ModelClient {\n");
-            sb.Append("  __Client: ").Append(__Client).Append("\n");
+            sb.Append("  _Client: ").Append(_Client).Append("\n");
             sb.Append("  AdditionalProperties: ").Append(AdditionalProperties).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
@@ -106,8 +106,8 @@ namespace Org.OpenAPITools.Model
             unchecked // Overflow is fine, just wrap
             {
                 int hashCode = 41;
-                if (this.__Client != null)
-                    hashCode = hashCode * 59 + this.__Client.GetHashCode();
+                if (this._Client != null)
+                    hashCode = hashCode * 59 + this._Client.GetHashCode();
                 if (this.AdditionalProperties != null)
                     hashCode = hashCode * 59 + this.AdditionalProperties.GetHashCode();
                 return hashCode;
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Model/SpecialModelName.cs
index f7199da4c03..26861d98d34 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -36,9 +36,11 @@ namespace Org.OpenAPITools.Model
         /// Initializes a new instance of the <see cref="SpecialModelName" /> class.
         /// </summary>
         /// <param name="specialPropertyName">specialPropertyName.</param>
-        public SpecialModelName(long specialPropertyName = default(long))
+        /// <param name="specialModelName">specialModelName.</param>
+        public SpecialModelName(long specialPropertyName = default(long), string specialModelName = default(string))
         {
             this.SpecialPropertyName = specialPropertyName;
+            this._SpecialModelName = specialModelName;
             this.AdditionalProperties = new Dictionary<string, object>();
         }
 
@@ -48,6 +50,12 @@ namespace Org.OpenAPITools.Model
         [DataMember(Name = "$special[property.name]", EmitDefaultValue = false)]
         public long SpecialPropertyName { get; set; }
 
+        /// <summary>
+        /// Gets or Sets _SpecialModelName
+        /// </summary>
+        [DataMember(Name = "_special_model.name_", EmitDefaultValue = false)]
+        public string _SpecialModelName { get; set; }
+
         /// <summary>
         /// Gets or Sets additional properties
         /// </summary>
@@ -63,6 +71,7 @@ namespace Org.OpenAPITools.Model
             var sb = new StringBuilder();
             sb.Append("class SpecialModelName {\n");
             sb.Append("  SpecialPropertyName: ").Append(SpecialPropertyName).Append("\n");
+            sb.Append("  _SpecialModelName: ").Append(_SpecialModelName).Append("\n");
             sb.Append("  AdditionalProperties: ").Append(AdditionalProperties).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
@@ -107,6 +116,8 @@ namespace Org.OpenAPITools.Model
             {
                 int hashCode = 41;
                 hashCode = hashCode * 59 + this.SpecialPropertyName.GetHashCode();
+                if (this._SpecialModelName != null)
+                    hashCode = hashCode * 59 + this._SpecialModelName.GetHashCode();
                 if (this.AdditionalProperties != null)
                     hashCode = hashCode * 59 + this.AdditionalProperties.GetHashCode();
                 return hashCode;
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/docs/ModelClient.md b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/docs/ModelClient.md
index 8a1bd169a2f..c29a6287433 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/docs/ModelClient.md
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/docs/ModelClient.md
@@ -4,7 +4,7 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**__Client** | **string** |  | [optional] 
+**_Client** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/docs/SpecialModelName.md b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/docs/SpecialModelName.md
index a27e685165a..648179799e1 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/docs/SpecialModelName.md
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/docs/SpecialModelName.md
@@ -5,6 +5,7 @@
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
 **SpecialPropertyName** | **long** |  | [optional] 
+**_SpecialModelName** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Model/ModelClient.cs
index 16f1dc95bab..4ee431a9b2f 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -38,15 +38,15 @@ namespace Org.OpenAPITools.Model
         /// <param name="_client">_client.</param>
         public ModelClient(string _client = default(string))
         {
-            this.__Client = _client;
+            this._Client = _client;
             this.AdditionalProperties = new Dictionary<string, object>();
         }
 
         /// <summary>
-        /// Gets or Sets __Client
+        /// Gets or Sets _Client
         /// </summary>
         [DataMember(Name = "client", EmitDefaultValue = false)]
-        public string __Client { get; set; }
+        public string _Client { get; set; }
 
         /// <summary>
         /// Gets or Sets additional properties
@@ -62,7 +62,7 @@ namespace Org.OpenAPITools.Model
         {
             var sb = new StringBuilder();
             sb.Append("class ModelClient {\n");
-            sb.Append("  __Client: ").Append(__Client).Append("\n");
+            sb.Append("  _Client: ").Append(_Client).Append("\n");
             sb.Append("  AdditionalProperties: ").Append(AdditionalProperties).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
@@ -106,8 +106,8 @@ namespace Org.OpenAPITools.Model
             unchecked // Overflow is fine, just wrap
             {
                 int hashCode = 41;
-                if (this.__Client != null)
-                    hashCode = hashCode * 59 + this.__Client.GetHashCode();
+                if (this._Client != null)
+                    hashCode = hashCode * 59 + this._Client.GetHashCode();
                 if (this.AdditionalProperties != null)
                     hashCode = hashCode * 59 + this.AdditionalProperties.GetHashCode();
                 return hashCode;
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Model/SpecialModelName.cs
index f7199da4c03..26861d98d34 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -36,9 +36,11 @@ namespace Org.OpenAPITools.Model
         /// Initializes a new instance of the <see cref="SpecialModelName" /> class.
         /// </summary>
         /// <param name="specialPropertyName">specialPropertyName.</param>
-        public SpecialModelName(long specialPropertyName = default(long))
+        /// <param name="specialModelName">specialModelName.</param>
+        public SpecialModelName(long specialPropertyName = default(long), string specialModelName = default(string))
         {
             this.SpecialPropertyName = specialPropertyName;
+            this._SpecialModelName = specialModelName;
             this.AdditionalProperties = new Dictionary<string, object>();
         }
 
@@ -48,6 +50,12 @@ namespace Org.OpenAPITools.Model
         [DataMember(Name = "$special[property.name]", EmitDefaultValue = false)]
         public long SpecialPropertyName { get; set; }
 
+        /// <summary>
+        /// Gets or Sets _SpecialModelName
+        /// </summary>
+        [DataMember(Name = "_special_model.name_", EmitDefaultValue = false)]
+        public string _SpecialModelName { get; set; }
+
         /// <summary>
         /// Gets or Sets additional properties
         /// </summary>
@@ -63,6 +71,7 @@ namespace Org.OpenAPITools.Model
             var sb = new StringBuilder();
             sb.Append("class SpecialModelName {\n");
             sb.Append("  SpecialPropertyName: ").Append(SpecialPropertyName).Append("\n");
+            sb.Append("  _SpecialModelName: ").Append(_SpecialModelName).Append("\n");
             sb.Append("  AdditionalProperties: ").Append(AdditionalProperties).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
@@ -107,6 +116,8 @@ namespace Org.OpenAPITools.Model
             {
                 int hashCode = 41;
                 hashCode = hashCode * 59 + this.SpecialPropertyName.GetHashCode();
+                if (this._SpecialModelName != null)
+                    hashCode = hashCode * 59 + this._SpecialModelName.GetHashCode();
                 if (this.AdditionalProperties != null)
                     hashCode = hashCode * 59 + this.AdditionalProperties.GetHashCode();
                 return hashCode;
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/docs/ModelClient.md b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/docs/ModelClient.md
index 8a1bd169a2f..c29a6287433 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/docs/ModelClient.md
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/docs/ModelClient.md
@@ -4,7 +4,7 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**__Client** | **string** |  | [optional] 
+**_Client** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/docs/SpecialModelName.md b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/docs/SpecialModelName.md
index a27e685165a..648179799e1 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/docs/SpecialModelName.md
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/docs/SpecialModelName.md
@@ -5,6 +5,7 @@
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
 **SpecialPropertyName** | **long** |  | [optional] 
+**_SpecialModelName** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Model/ModelClient.cs
index 16f1dc95bab..4ee431a9b2f 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -38,15 +38,15 @@ namespace Org.OpenAPITools.Model
         /// <param name="_client">_client.</param>
         public ModelClient(string _client = default(string))
         {
-            this.__Client = _client;
+            this._Client = _client;
             this.AdditionalProperties = new Dictionary<string, object>();
         }
 
         /// <summary>
-        /// Gets or Sets __Client
+        /// Gets or Sets _Client
         /// </summary>
         [DataMember(Name = "client", EmitDefaultValue = false)]
-        public string __Client { get; set; }
+        public string _Client { get; set; }
 
         /// <summary>
         /// Gets or Sets additional properties
@@ -62,7 +62,7 @@ namespace Org.OpenAPITools.Model
         {
             var sb = new StringBuilder();
             sb.Append("class ModelClient {\n");
-            sb.Append("  __Client: ").Append(__Client).Append("\n");
+            sb.Append("  _Client: ").Append(_Client).Append("\n");
             sb.Append("  AdditionalProperties: ").Append(AdditionalProperties).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
@@ -106,8 +106,8 @@ namespace Org.OpenAPITools.Model
             unchecked // Overflow is fine, just wrap
             {
                 int hashCode = 41;
-                if (this.__Client != null)
-                    hashCode = hashCode * 59 + this.__Client.GetHashCode();
+                if (this._Client != null)
+                    hashCode = hashCode * 59 + this._Client.GetHashCode();
                 if (this.AdditionalProperties != null)
                     hashCode = hashCode * 59 + this.AdditionalProperties.GetHashCode();
                 return hashCode;
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Model/SpecialModelName.cs
index f7199da4c03..26861d98d34 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -36,9 +36,11 @@ namespace Org.OpenAPITools.Model
         /// Initializes a new instance of the <see cref="SpecialModelName" /> class.
         /// </summary>
         /// <param name="specialPropertyName">specialPropertyName.</param>
-        public SpecialModelName(long specialPropertyName = default(long))
+        /// <param name="specialModelName">specialModelName.</param>
+        public SpecialModelName(long specialPropertyName = default(long), string specialModelName = default(string))
         {
             this.SpecialPropertyName = specialPropertyName;
+            this._SpecialModelName = specialModelName;
             this.AdditionalProperties = new Dictionary<string, object>();
         }
 
@@ -48,6 +50,12 @@ namespace Org.OpenAPITools.Model
         [DataMember(Name = "$special[property.name]", EmitDefaultValue = false)]
         public long SpecialPropertyName { get; set; }
 
+        /// <summary>
+        /// Gets or Sets _SpecialModelName
+        /// </summary>
+        [DataMember(Name = "_special_model.name_", EmitDefaultValue = false)]
+        public string _SpecialModelName { get; set; }
+
         /// <summary>
         /// Gets or Sets additional properties
         /// </summary>
@@ -63,6 +71,7 @@ namespace Org.OpenAPITools.Model
             var sb = new StringBuilder();
             sb.Append("class SpecialModelName {\n");
             sb.Append("  SpecialPropertyName: ").Append(SpecialPropertyName).Append("\n");
+            sb.Append("  _SpecialModelName: ").Append(_SpecialModelName).Append("\n");
             sb.Append("  AdditionalProperties: ").Append(AdditionalProperties).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
@@ -107,6 +116,8 @@ namespace Org.OpenAPITools.Model
             {
                 int hashCode = 41;
                 hashCode = hashCode * 59 + this.SpecialPropertyName.GetHashCode();
+                if (this._SpecialModelName != null)
+                    hashCode = hashCode * 59 + this._SpecialModelName.GetHashCode();
                 if (this.AdditionalProperties != null)
                     hashCode = hashCode * 59 + this.AdditionalProperties.GetHashCode();
                 return hashCode;
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient/docs/ModelClient.md b/samples/client/petstore/csharp-netcore/OpenAPIClient/docs/ModelClient.md
index 8a1bd169a2f..c29a6287433 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient/docs/ModelClient.md
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient/docs/ModelClient.md
@@ -4,7 +4,7 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**__Client** | **string** |  | [optional] 
+**_Client** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient/docs/SpecialModelName.md b/samples/client/petstore/csharp-netcore/OpenAPIClient/docs/SpecialModelName.md
index a27e685165a..648179799e1 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient/docs/SpecialModelName.md
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient/docs/SpecialModelName.md
@@ -5,6 +5,7 @@
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
 **SpecialPropertyName** | **long** |  | [optional] 
+**_SpecialModelName** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/ModelClient.cs
index 16f1dc95bab..4ee431a9b2f 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -38,15 +38,15 @@ namespace Org.OpenAPITools.Model
         /// <param name="_client">_client.</param>
         public ModelClient(string _client = default(string))
         {
-            this.__Client = _client;
+            this._Client = _client;
             this.AdditionalProperties = new Dictionary<string, object>();
         }
 
         /// <summary>
-        /// Gets or Sets __Client
+        /// Gets or Sets _Client
         /// </summary>
         [DataMember(Name = "client", EmitDefaultValue = false)]
-        public string __Client { get; set; }
+        public string _Client { get; set; }
 
         /// <summary>
         /// Gets or Sets additional properties
@@ -62,7 +62,7 @@ namespace Org.OpenAPITools.Model
         {
             var sb = new StringBuilder();
             sb.Append("class ModelClient {\n");
-            sb.Append("  __Client: ").Append(__Client).Append("\n");
+            sb.Append("  _Client: ").Append(_Client).Append("\n");
             sb.Append("  AdditionalProperties: ").Append(AdditionalProperties).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
@@ -106,8 +106,8 @@ namespace Org.OpenAPITools.Model
             unchecked // Overflow is fine, just wrap
             {
                 int hashCode = 41;
-                if (this.__Client != null)
-                    hashCode = hashCode * 59 + this.__Client.GetHashCode();
+                if (this._Client != null)
+                    hashCode = hashCode * 59 + this._Client.GetHashCode();
                 if (this.AdditionalProperties != null)
                     hashCode = hashCode * 59 + this.AdditionalProperties.GetHashCode();
                 return hashCode;
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/SpecialModelName.cs
index f7199da4c03..26861d98d34 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -36,9 +36,11 @@ namespace Org.OpenAPITools.Model
         /// Initializes a new instance of the <see cref="SpecialModelName" /> class.
         /// </summary>
         /// <param name="specialPropertyName">specialPropertyName.</param>
-        public SpecialModelName(long specialPropertyName = default(long))
+        /// <param name="specialModelName">specialModelName.</param>
+        public SpecialModelName(long specialPropertyName = default(long), string specialModelName = default(string))
         {
             this.SpecialPropertyName = specialPropertyName;
+            this._SpecialModelName = specialModelName;
             this.AdditionalProperties = new Dictionary<string, object>();
         }
 
@@ -48,6 +50,12 @@ namespace Org.OpenAPITools.Model
         [DataMember(Name = "$special[property.name]", EmitDefaultValue = false)]
         public long SpecialPropertyName { get; set; }
 
+        /// <summary>
+        /// Gets or Sets _SpecialModelName
+        /// </summary>
+        [DataMember(Name = "_special_model.name_", EmitDefaultValue = false)]
+        public string _SpecialModelName { get; set; }
+
         /// <summary>
         /// Gets or Sets additional properties
         /// </summary>
@@ -63,6 +71,7 @@ namespace Org.OpenAPITools.Model
             var sb = new StringBuilder();
             sb.Append("class SpecialModelName {\n");
             sb.Append("  SpecialPropertyName: ").Append(SpecialPropertyName).Append("\n");
+            sb.Append("  _SpecialModelName: ").Append(_SpecialModelName).Append("\n");
             sb.Append("  AdditionalProperties: ").Append(AdditionalProperties).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
@@ -107,6 +116,8 @@ namespace Org.OpenAPITools.Model
             {
                 int hashCode = 41;
                 hashCode = hashCode * 59 + this.SpecialPropertyName.GetHashCode();
+                if (this._SpecialModelName != null)
+                    hashCode = hashCode * 59 + this._SpecialModelName.GetHashCode();
                 if (this.AdditionalProperties != null)
                     hashCode = hashCode * 59 + this.AdditionalProperties.GetHashCode();
                 return hashCode;
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/docs/ModelClient.md b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/docs/ModelClient.md
index 8a1bd169a2f..c29a6287433 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/docs/ModelClient.md
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/docs/ModelClient.md
@@ -4,7 +4,7 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**__Client** | **string** |  | [optional] 
+**_Client** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/docs/SpecialModelName.md b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/docs/SpecialModelName.md
index a27e685165a..648179799e1 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/docs/SpecialModelName.md
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/docs/SpecialModelName.md
@@ -5,6 +5,7 @@
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
 **SpecialPropertyName** | **long** |  | [optional] 
+**_SpecialModelName** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Model/ModelClient.cs
index 09257478b56..45be979525c 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -38,14 +38,14 @@ namespace Org.OpenAPITools.Model
         /// <param name="_client">_client.</param>
         public ModelClient(string _client = default(string))
         {
-            this.__Client = _client;
+            this._Client = _client;
         }
 
         /// <summary>
-        /// Gets or Sets __Client
+        /// Gets or Sets _Client
         /// </summary>
         [DataMember(Name = "client", EmitDefaultValue = false)]
-        public string __Client { get; set; }
+        public string _Client { get; set; }
 
         /// <summary>
         /// Returns the string presentation of the object
@@ -55,7 +55,7 @@ namespace Org.OpenAPITools.Model
         {
             var sb = new StringBuilder();
             sb.Append("class ModelClient {\n");
-            sb.Append("  __Client: ").Append(__Client).Append("\n");
+            sb.Append("  _Client: ").Append(_Client).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
         }
@@ -98,8 +98,8 @@ namespace Org.OpenAPITools.Model
             unchecked // Overflow is fine, just wrap
             {
                 int hashCode = 41;
-                if (this.__Client != null)
-                    hashCode = hashCode * 59 + this.__Client.GetHashCode();
+                if (this._Client != null)
+                    hashCode = hashCode * 59 + this._Client.GetHashCode();
                 return hashCode;
             }
         }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Model/SpecialModelName.cs b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Model/SpecialModelName.cs
index c467ab0c57d..7f69f554b46 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Model/SpecialModelName.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Model/SpecialModelName.cs
@@ -36,9 +36,11 @@ namespace Org.OpenAPITools.Model
         /// Initializes a new instance of the <see cref="SpecialModelName" /> class.
         /// </summary>
         /// <param name="specialPropertyName">specialPropertyName.</param>
-        public SpecialModelName(long specialPropertyName = default(long))
+        /// <param name="specialModelName">specialModelName.</param>
+        public SpecialModelName(long specialPropertyName = default(long), string specialModelName = default(string))
         {
             this.SpecialPropertyName = specialPropertyName;
+            this._SpecialModelName = specialModelName;
         }
 
         /// <summary>
@@ -47,6 +49,12 @@ namespace Org.OpenAPITools.Model
         [DataMember(Name = "$special[property.name]", EmitDefaultValue = false)]
         public long SpecialPropertyName { get; set; }
 
+        /// <summary>
+        /// Gets or Sets _SpecialModelName
+        /// </summary>
+        [DataMember(Name = "_special_model.name_", EmitDefaultValue = false)]
+        public string _SpecialModelName { get; set; }
+
         /// <summary>
         /// Returns the string presentation of the object
         /// </summary>
@@ -56,6 +64,7 @@ namespace Org.OpenAPITools.Model
             var sb = new StringBuilder();
             sb.Append("class SpecialModelName {\n");
             sb.Append("  SpecialPropertyName: ").Append(SpecialPropertyName).Append("\n");
+            sb.Append("  _SpecialModelName: ").Append(_SpecialModelName).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
         }
@@ -99,6 +108,8 @@ namespace Org.OpenAPITools.Model
             {
                 int hashCode = 41;
                 hashCode = hashCode * 59 + this.SpecialPropertyName.GetHashCode();
+                if (this._SpecialModelName != null)
+                    hashCode = hashCode * 59 + this._SpecialModelName.GetHashCode();
                 return hashCode;
             }
         }
diff --git a/samples/client/petstore/csharp/OpenAPIClient/docs/ModelClient.md b/samples/client/petstore/csharp/OpenAPIClient/docs/ModelClient.md
index e36e1fad802..80bd5d6edba 100644
--- a/samples/client/petstore/csharp/OpenAPIClient/docs/ModelClient.md
+++ b/samples/client/petstore/csharp/OpenAPIClient/docs/ModelClient.md
@@ -5,7 +5,7 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**__Client** | **string** |  | [optional] 
+**_Client** | **string** |  | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models)
 [[Back to API list]](../README.md#documentation-for-api-endpoints)
diff --git a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Model/ModelClient.cs b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Model/ModelClient.cs
index 15d88accfdc..9c1e8a26e5c 100644
--- a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Model/ModelClient.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Model/ModelClient.cs
@@ -36,14 +36,14 @@ namespace Org.OpenAPITools.Model
         /// <param name="_client">_client.</param>
         public ModelClient(string _client = default(string))
         {
-            this.__Client = _client;
+            this._Client = _client;
         }
 
         /// <summary>
-        /// Gets or Sets __Client
+        /// Gets or Sets _Client
         /// </summary>
         [DataMember(Name="client", EmitDefaultValue=false)]
-        public string __Client { get; set; }
+        public string _Client { get; set; }
 
         /// <summary>
         /// Returns the string presentation of the object
@@ -53,7 +53,7 @@ namespace Org.OpenAPITools.Model
         {
             var sb = new StringBuilder();
             sb.Append("class ModelClient {\n");
-            sb.Append("  __Client: ").Append(__Client).Append("\n");
+            sb.Append("  _Client: ").Append(_Client).Append("\n");
             sb.Append("}\n");
             return sb.ToString();
         }
@@ -89,9 +89,9 @@ namespace Org.OpenAPITools.Model
 
             return 
                 (
-                    this.__Client == input.__Client ||
-                    (this.__Client != null &&
-                    this.__Client.Equals(input.__Client))
+                    this._Client == input._Client ||
+                    (this._Client != null &&
+                    this._Client.Equals(input._Client))
                 );
         }
 
@@ -104,8 +104,8 @@ namespace Org.OpenAPITools.Model
             unchecked // Overflow is fine, just wrap
             {
                 int hashCode = 41;
-                if (this.__Client != null)
-                    hashCode = hashCode * 59 + this.__Client.GetHashCode();
+                if (this._Client != null)
+                    hashCode = hashCode * 59 + this._Client.GetHashCode();
                 return hashCode;
             }
         }
diff --git a/samples/openapi3/client/petstore/java/jersey2-java8/api/openapi.yaml b/samples/openapi3/client/petstore/java/jersey2-java8/api/openapi.yaml
index 1e5c6be79a3..0ef965969a7 100644
--- a/samples/openapi3/client/petstore/java/jersey2-java8/api/openapi.yaml
+++ b/samples/openapi3/client/petstore/java/jersey2-java8/api/openapi.yaml
@@ -1957,6 +1957,8 @@ components:
         $special[property.name]:
           format: int64
           type: integer
+        _special_model.name_:
+          type: string
       xml:
         name: $special[model.name]
     HealthCheckResult:
diff --git a/samples/openapi3/client/petstore/java/jersey2-java8/docs/SpecialModelName.md b/samples/openapi3/client/petstore/java/jersey2-java8/docs/SpecialModelName.md
index 2692c1caafe..352611142df 100644
--- a/samples/openapi3/client/petstore/java/jersey2-java8/docs/SpecialModelName.md
+++ b/samples/openapi3/client/petstore/java/jersey2-java8/docs/SpecialModelName.md
@@ -8,6 +8,7 @@
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
 **$specialPropertyName** | **Long** |  |  [optional]
+**specialModelName** | **String** |  |  [optional]
 
 
 
diff --git a/samples/openapi3/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/SpecialModelName.java b/samples/openapi3/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/SpecialModelName.java
index f72fc3538e2..3adc9c06ff3 100644
--- a/samples/openapi3/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/SpecialModelName.java
+++ b/samples/openapi3/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/SpecialModelName.java
@@ -32,13 +32,17 @@ import org.openapitools.client.JSON;
  * SpecialModelName
  */
 @JsonPropertyOrder({
-  SpecialModelName.JSON_PROPERTY_$_SPECIAL_PROPERTY_NAME
+  SpecialModelName.JSON_PROPERTY_$_SPECIAL_PROPERTY_NAME,
+  SpecialModelName.JSON_PROPERTY_SPECIAL_MODEL_NAME
 })
 @javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
 public class SpecialModelName {
   public static final String JSON_PROPERTY_$_SPECIAL_PROPERTY_NAME = "$special[property.name]";
   private Long $specialPropertyName;
 
+  public static final String JSON_PROPERTY_SPECIAL_MODEL_NAME = "_special_model.name_";
+  private String specialModelName;
+
 
   public SpecialModelName $specialPropertyName(Long $specialPropertyName) {
     this.$specialPropertyName = $specialPropertyName;
@@ -64,6 +68,30 @@ public class SpecialModelName {
   }
 
 
+  public SpecialModelName specialModelName(String specialModelName) {
+    this.specialModelName = specialModelName;
+    return this;
+  }
+
+   /**
+   * Get specialModelName
+   * @return specialModelName
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_SPECIAL_MODEL_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getSpecialModelName() {
+    return specialModelName;
+  }
+
+
+  public void setSpecialModelName(String specialModelName) {
+    this.specialModelName = specialModelName;
+  }
+
+
   /**
    * Return true if this _special_model.name_ object is equal to o.
    */
@@ -76,12 +104,13 @@ public class SpecialModelName {
       return false;
     }
     SpecialModelName specialModelName = (SpecialModelName) o;
-    return Objects.equals(this.$specialPropertyName, specialModelName.$specialPropertyName);
+    return Objects.equals(this.$specialPropertyName, specialModelName.$specialPropertyName) &&
+        Objects.equals(this.specialModelName, specialModelName.specialModelName);
   }
 
   @Override
   public int hashCode() {
-    return Objects.hash($specialPropertyName);
+    return Objects.hash($specialPropertyName, specialModelName);
   }
 
   @Override
@@ -89,6 +118,7 @@ public class SpecialModelName {
     StringBuilder sb = new StringBuilder();
     sb.append("class SpecialModelName {\n");
     sb.append("    $specialPropertyName: ").append(toIndentedString($specialPropertyName)).append("\n");
+    sb.append("    specialModelName: ").append(toIndentedString(specialModelName)).append("\n");
     sb.append("}");
     return sb.toString();
   }
diff --git a/samples/openapi3/client/petstore/java/native/api/openapi.yaml b/samples/openapi3/client/petstore/java/native/api/openapi.yaml
index 1e5c6be79a3..0ef965969a7 100644
--- a/samples/openapi3/client/petstore/java/native/api/openapi.yaml
+++ b/samples/openapi3/client/petstore/java/native/api/openapi.yaml
@@ -1957,6 +1957,8 @@ components:
         $special[property.name]:
           format: int64
           type: integer
+        _special_model.name_:
+          type: string
       xml:
         name: $special[model.name]
     HealthCheckResult:
diff --git a/samples/openapi3/client/petstore/java/native/docs/SpecialModelName.md b/samples/openapi3/client/petstore/java/native/docs/SpecialModelName.md
index 2692c1caafe..352611142df 100644
--- a/samples/openapi3/client/petstore/java/native/docs/SpecialModelName.md
+++ b/samples/openapi3/client/petstore/java/native/docs/SpecialModelName.md
@@ -8,6 +8,7 @@
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
 **$specialPropertyName** | **Long** |  |  [optional]
+**specialModelName** | **String** |  |  [optional]
 
 
 
diff --git a/samples/openapi3/client/petstore/java/native/src/main/java/org/openapitools/client/model/SpecialModelName.java b/samples/openapi3/client/petstore/java/native/src/main/java/org/openapitools/client/model/SpecialModelName.java
index 9d3397e2241..cabc24f175a 100644
--- a/samples/openapi3/client/petstore/java/native/src/main/java/org/openapitools/client/model/SpecialModelName.java
+++ b/samples/openapi3/client/petstore/java/native/src/main/java/org/openapitools/client/model/SpecialModelName.java
@@ -31,13 +31,17 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
  * SpecialModelName
  */
 @JsonPropertyOrder({
-  SpecialModelName.JSON_PROPERTY_$_SPECIAL_PROPERTY_NAME
+  SpecialModelName.JSON_PROPERTY_$_SPECIAL_PROPERTY_NAME,
+  SpecialModelName.JSON_PROPERTY_SPECIAL_MODEL_NAME
 })
 @javax.annotation.processing.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
 public class SpecialModelName {
   public static final String JSON_PROPERTY_$_SPECIAL_PROPERTY_NAME = "$special[property.name]";
   private Long $specialPropertyName;
 
+  public static final String JSON_PROPERTY_SPECIAL_MODEL_NAME = "_special_model.name_";
+  private String specialModelName;
+
 
   public SpecialModelName $specialPropertyName(Long $specialPropertyName) {
     this.$specialPropertyName = $specialPropertyName;
@@ -63,6 +67,30 @@ public class SpecialModelName {
   }
 
 
+  public SpecialModelName specialModelName(String specialModelName) {
+    this.specialModelName = specialModelName;
+    return this;
+  }
+
+   /**
+   * Get specialModelName
+   * @return specialModelName
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_SPECIAL_MODEL_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getSpecialModelName() {
+    return specialModelName;
+  }
+
+
+  public void setSpecialModelName(String specialModelName) {
+    this.specialModelName = specialModelName;
+  }
+
+
   /**
    * Return true if this _special_model.name_ object is equal to o.
    */
@@ -75,12 +103,13 @@ public class SpecialModelName {
       return false;
     }
     SpecialModelName specialModelName = (SpecialModelName) o;
-    return Objects.equals(this.$specialPropertyName, specialModelName.$specialPropertyName);
+    return Objects.equals(this.$specialPropertyName, specialModelName.$specialPropertyName) &&
+        Objects.equals(this.specialModelName, specialModelName.specialModelName);
   }
 
   @Override
   public int hashCode() {
-    return Objects.hash($specialPropertyName);
+    return Objects.hash($specialPropertyName, specialModelName);
   }
 
   @Override
@@ -88,6 +117,7 @@ public class SpecialModelName {
     StringBuilder sb = new StringBuilder();
     sb.append("class SpecialModelName {\n");
     sb.append("    $specialPropertyName: ").append(toIndentedString($specialPropertyName)).append("\n");
+    sb.append("    specialModelName: ").append(toIndentedString(specialModelName)).append("\n");
     sb.append("}");
     return sb.toString();
   }