diff --git a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 53ce7dec4bc..3dcdcb72582 100644
--- a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -249,7 +249,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<ModelClient>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (ModelClient) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(ModelClient)));
         }
 
@@ -324,7 +324,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<ModelClient>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (ModelClient) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(ModelClient)));
         }
 
diff --git a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/FakeApi.cs
index d8b3e598376..dd82cf82c4a 100644
--- a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -815,7 +815,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<bool?>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (bool?) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(bool?)));
         }
 
@@ -886,7 +886,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<bool?>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (bool?) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(bool?)));
         }
 
@@ -956,7 +956,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<OuterComposite>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (OuterComposite) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(OuterComposite)));
         }
 
@@ -1027,7 +1027,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<OuterComposite>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (OuterComposite) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(OuterComposite)));
         }
 
@@ -1097,7 +1097,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<decimal?>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (decimal?) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(decimal?)));
         }
 
@@ -1168,7 +1168,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<decimal?>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (decimal?) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(decimal?)));
         }
 
@@ -1238,7 +1238,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<string>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (string) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(string)));
         }
 
@@ -1309,7 +1309,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<string>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (string) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(string)));
         }
 
@@ -1381,7 +1381,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1454,7 +1454,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1532,7 +1532,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1611,7 +1611,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1685,7 +1685,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<ModelClient>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (ModelClient) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(ModelClient)));
         }
 
@@ -1760,7 +1760,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<ModelClient>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (ModelClient) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(ModelClient)));
         }
 
@@ -1879,7 +1879,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1999,7 +1999,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -2082,7 +2082,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -2166,7 +2166,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -2251,7 +2251,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -2337,7 +2337,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -2409,7 +2409,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -2482,7 +2482,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -2553,7 +2553,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -2625,7 +2625,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
diff --git a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index eba1f35f96f..ce81e9db6d6 100644
--- a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -254,7 +254,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<ModelClient>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (ModelClient) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(ModelClient)));
         }
 
@@ -334,7 +334,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<ModelClient>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (ModelClient) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(ModelClient)));
         }
 
diff --git a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/PetApi.cs
index 21f74b3dd3b..cce1d9d5a44 100644
--- a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/PetApi.cs
@@ -618,7 +618,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -698,7 +698,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -771,7 +771,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -845,7 +845,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -918,7 +918,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<List<Pet>>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (List<Pet>) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(List<Pet>)));
         }
 
@@ -992,7 +992,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<List<Pet>>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (List<Pet>) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(List<Pet>)));
         }
 
@@ -1065,7 +1065,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<List<Pet>>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (List<Pet>) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(List<Pet>)));
         }
 
@@ -1139,7 +1139,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<List<Pet>>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (List<Pet>) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(List<Pet>)));
         }
 
@@ -1211,7 +1211,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Pet>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (Pet) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(Pet)));
         }
 
@@ -1284,7 +1284,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Pet>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (Pet) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(Pet)));
         }
 
@@ -1363,7 +1363,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1443,7 +1443,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1520,7 +1520,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1598,7 +1598,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1677,7 +1677,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<ApiResponse>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (ApiResponse) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(ApiResponse)));
         }
 
@@ -1757,7 +1757,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<ApiResponse>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (ApiResponse) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(ApiResponse)));
         }
 
@@ -1839,7 +1839,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<ApiResponse>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (ApiResponse) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(ApiResponse)));
         }
 
@@ -1922,7 +1922,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<ApiResponse>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (ApiResponse) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(ApiResponse)));
         }
 
diff --git a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/StoreApi.cs
index 0313b615afd..63aed225ad2 100644
--- a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -361,7 +361,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -426,7 +426,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -491,7 +491,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Dictionary<string, int?>>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (Dictionary<string, int?>) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(Dictionary<string, int?>)));
         }
 
@@ -557,7 +557,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Dictionary<string, int?>>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (Dictionary<string, int?>) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(Dictionary<string, int?>)));
         }
 
@@ -624,7 +624,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Order>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (Order) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(Order)));
         }
 
@@ -692,7 +692,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Order>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (Order) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(Order)));
         }
 
@@ -766,7 +766,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Order>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (Order) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(Order)));
         }
 
@@ -841,7 +841,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Order>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (Order) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(Order)));
         }
 
diff --git a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/UserApi.cs
index a75e965fa40..290bcc4e480 100644
--- a/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient/src/Org.OpenAPITools/Api/UserApi.cs
@@ -544,7 +544,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -616,7 +616,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -687,7 +687,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -759,7 +759,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -830,7 +830,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -902,7 +902,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -966,7 +966,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1031,7 +1031,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1098,7 +1098,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<User>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (User) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(User)));
         }
 
@@ -1166,7 +1166,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<User>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (User) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(User)));
         }
 
@@ -1239,7 +1239,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<string>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (string) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(string)));
         }
 
@@ -1313,7 +1313,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<string>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 (string) this.Configuration.ApiClient.Deserialize(localVarResponse, typeof(string)));
         }
 
@@ -1371,7 +1371,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1430,7 +1430,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1507,7 +1507,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }
 
@@ -1585,7 +1585,7 @@ namespace Org.OpenAPITools.Api
             }
 
             return new ApiResponse<Object>(localVarStatusCode,
-                localVarResponse.Headers.ToDictionary(x => x.Name, x => x.Value.ToString()),
+                localVarResponse.Headers.ToDictionary(x => x.Name, x => string.Join(",", x.Value)),
                 null);
         }