diff --git a/modules/swagger-codegen/src/main/resources/csharp/api.mustache b/modules/swagger-codegen/src/main/resources/csharp/api.mustache
index 1ae2921849d..084caf97b9b 100644
--- a/modules/swagger-codegen/src/main/resources/csharp/api.mustache
+++ b/modules/swagger-codegen/src/main/resources/csharp/api.mustache
@@ -40,7 +40,7 @@ namespace {{package}} {
     /// <returns></returns>
     public {{#returnType}}{{{returnType}}} {{/returnType}}{{^returnType}}void {{/returnType}} {{nickname}} ({{#allParams}}{{{dataType}}} {{paramName}}{{#hasMore}}, {{/hasMore}}{{/allParams}}) {
       // create path and map variables
-      var path = "{{path}}".Replace("{format}","json"){{#pathParams}}.Replace("{" + "{{baseName}}" + "}", apiInvoker.escapeString({{{paramName}}}.ToString())){{/pathParams}};
+      var path = "{{path}}".Replace("{format}","json"){{#pathParams}}.Replace("{" + "{{baseName}}" + "}", apiInvoker.ParameterToString({{{paramName}}})){{/pathParams}};
 
       // query params
       var queryParams = new Dictionary<String, String>();
@@ -55,20 +55,18 @@ namespace {{package}} {
       {{/requiredParamCount}}
 
       {{#queryParams}}if ({{paramName}} != null){
-        string paramStr = ({{paramName}} is DateTime) ? ((DateTime)(object){{paramName}}).ToString("u") : Convert.ToString({{paramName}});
-        queryParams.Add("{{baseName}}", paramStr);
+        queryParams.Add("{{baseName}}", apiInvoker.ParameterToString({{paramName}}));
       }
       {{/queryParams}}
 
-      {{#headerParams}}headerParams.Add("{{baseName}}", {{paramName}});
+      {{#headerParams}}headerParams.Add("{{baseName}}", apiInvoker.ParameterToString({{paramName}}));
       {{/headerParams}}
 
       {{#formParams}}if ({{paramName}} != null){
         if({{paramName}} is byte[]) {
           formParams.Add("{{baseName}}", {{paramName}});
         } else {
-          string paramStr = ({{paramName}} is DateTime) ? ((DateTime)(object){{paramName}}).ToString("u") : Convert.ToString({{paramName}});
-          formParams.Add("{{baseName}}", paramStr);
+          formParams.Add("{{baseName}}", apiInvoker.ParameterToString({{paramName}}));
         }
       }
       {{/formParams}}
diff --git a/modules/swagger-codegen/src/main/resources/csharp/apiInvoker.mustache b/modules/swagger-codegen/src/main/resources/csharp/apiInvoker.mustache
index f7c76ee2c56..4e7f1b6997b 100644
--- a/modules/swagger-codegen/src/main/resources/csharp/apiInvoker.mustache
+++ b/modules/swagger-codegen/src/main/resources/csharp/apiInvoker.mustache
@@ -15,14 +15,41 @@
         return _instance;
       }
 
+      /// <summary>
+      /// Add default header
+      /// </summary>
+      /// <param name="key">  Header field name
+      /// <param name="value"> Header field value
+      /// <returns></returns>
       public void addDefaultHeader(string key, string value) {
          defaultHeaderMap.Add(key, value);
       }
 
+      /// <summary>
+      /// escape string (url-encoded)
+      /// </summary>
+      /// <param name="str"> String to be escaped
+      /// <returns>Escaped string</returns>
       public string escapeString(string str) {
         return str;
       }
 
+      /// <summary>
+      /// if parameter is DateTime, output in ISO8601 format, otherwise just return the string
+      /// </summary>
+      /// <param name="obj"> The parameter (header, path, query, form)
+      /// <returns>Formatted string</returns>
+      public string ParameterToString(object obj)
+      {
+        return (obj is DateTime) ? ((DateTime)obj).ToString ("u") : Convert.ToString (obj);
+      }
+
+      /// <summary>
+      /// Deserialize the JSON string into a proper object
+      /// </summary>
+      /// <param name="json"> JSON string
+      /// <param name="type"> Object type
+      /// <returns>Object representation of the JSON string</returns>
       public static object deserialize(string json, Type type) {
         try
         {
@@ -99,6 +126,7 @@
               case "GET":
                   break;
               case "POST":
+              case "PATCH":
               case "PUT":
               case "DELETE":
                   using (Stream requestStream = client.GetRequestStream())
diff --git a/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/PetApi.cs b/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/PetApi.cs
index 36bb469686a..3750f302faa 100644
--- a/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/PetApi.cs
@@ -144,8 +144,7 @@ namespace io.swagger.Api {
       
 
       if (Status != null){
-        string paramStr = (Status is DateTime) ? ((DateTime)(object)Status).ToString("u") : Convert.ToString(Status);
-        queryParams.Add("status", paramStr);
+        queryParams.Add("status", apiInvoker.ParameterToString(Status));
       }
       
 
@@ -201,8 +200,7 @@ namespace io.swagger.Api {
       
 
       if (Tags != null){
-        string paramStr = (Tags is DateTime) ? ((DateTime)(object)Tags).ToString("u") : Convert.ToString(Tags);
-        queryParams.Add("tags", paramStr);
+        queryParams.Add("tags", apiInvoker.ParameterToString(Tags));
       }
       
 
@@ -248,7 +246,7 @@ namespace io.swagger.Api {
     /// <returns></returns>
     public Pet  getPetById (long? PetId) {
       // create path and map variables
-      var path = "/pet/{petId}".Replace("{format}","json").Replace("{" + "petId" + "}", apiInvoker.escapeString(PetId.ToString()));
+      var path = "/pet/{petId}".Replace("{format}","json").Replace("{" + "petId" + "}", apiInvoker.ParameterToString(PetId));
 
       // query params
       var queryParams = new Dictionary<String, String>();
@@ -303,7 +301,7 @@ namespace io.swagger.Api {
     /// <returns></returns>
     public void  updatePetWithForm (string PetId, string Name, string Status) {
       // create path and map variables
-      var path = "/pet/{petId}".Replace("{format}","json").Replace("{" + "petId" + "}", apiInvoker.escapeString(PetId.ToString()));
+      var path = "/pet/{petId}".Replace("{format}","json").Replace("{" + "petId" + "}", apiInvoker.ParameterToString(PetId));
 
       // query params
       var queryParams = new Dictionary<String, String>();
@@ -320,16 +318,14 @@ namespace io.swagger.Api {
         if(Name is byte[]) {
           formParams.Add("name", Name);
         } else {
-          string paramStr = (Name is DateTime) ? ((DateTime)(object)Name).ToString("u") : Convert.ToString(Name);
-          formParams.Add("name", paramStr);
+          formParams.Add("name", apiInvoker.ParameterToString(Name));
         }
       }
       if (Status != null){
         if(Status is byte[]) {
           formParams.Add("status", Status);
         } else {
-          string paramStr = (Status is DateTime) ? ((DateTime)(object)Status).ToString("u") : Convert.ToString(Status);
-          formParams.Add("status", paramStr);
+          formParams.Add("status", apiInvoker.ParameterToString(Status));
         }
       }
       
@@ -368,7 +364,7 @@ namespace io.swagger.Api {
     /// <returns></returns>
     public void  deletePet (string ApiKey, long? PetId) {
       // create path and map variables
-      var path = "/pet/{petId}".Replace("{format}","json").Replace("{" + "petId" + "}", apiInvoker.escapeString(PetId.ToString()));
+      var path = "/pet/{petId}".Replace("{format}","json").Replace("{" + "petId" + "}", apiInvoker.ParameterToString(PetId));
 
       // query params
       var queryParams = new Dictionary<String, String>();
@@ -379,7 +375,7 @@ namespace io.swagger.Api {
 
       
 
-      headerParams.Add("api_key", ApiKey);
+      headerParams.Add("api_key", apiInvoker.ParameterToString(ApiKey));
       
 
       
@@ -419,7 +415,7 @@ namespace io.swagger.Api {
     /// <returns></returns>
     public void  uploadFile (long? PetId, string AdditionalMetadata, byte[] File) {
       // create path and map variables
-      var path = "/pet/{petId}/uploadImage".Replace("{format}","json").Replace("{" + "petId" + "}", apiInvoker.escapeString(PetId.ToString()));
+      var path = "/pet/{petId}/uploadImage".Replace("{format}","json").Replace("{" + "petId" + "}", apiInvoker.ParameterToString(PetId));
 
       // query params
       var queryParams = new Dictionary<String, String>();
@@ -436,16 +432,14 @@ namespace io.swagger.Api {
         if(AdditionalMetadata is byte[]) {
           formParams.Add("additionalMetadata", AdditionalMetadata);
         } else {
-          string paramStr = (AdditionalMetadata is DateTime) ? ((DateTime)(object)AdditionalMetadata).ToString("u") : Convert.ToString(AdditionalMetadata);
-          formParams.Add("additionalMetadata", paramStr);
+          formParams.Add("additionalMetadata", apiInvoker.ParameterToString(AdditionalMetadata));
         }
       }
       if (File != null){
         if(File is byte[]) {
           formParams.Add("file", File);
         } else {
-          string paramStr = (File is DateTime) ? ((DateTime)(object)File).ToString("u") : Convert.ToString(File);
-          formParams.Add("file", paramStr);
+          formParams.Add("file", apiInvoker.ParameterToString(File));
         }
       }
       
diff --git a/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/StoreApi.cs b/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/StoreApi.cs
index 04c5ed0dc90..6ab79f87976 100644
--- a/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/StoreApi.cs
@@ -143,7 +143,7 @@ namespace io.swagger.Api {
     /// <returns></returns>
     public Order  getOrderById (string OrderId) {
       // create path and map variables
-      var path = "/store/order/{orderId}".Replace("{format}","json").Replace("{" + "orderId" + "}", apiInvoker.escapeString(OrderId.ToString()));
+      var path = "/store/order/{orderId}".Replace("{format}","json").Replace("{" + "orderId" + "}", apiInvoker.ParameterToString(OrderId));
 
       // query params
       var queryParams = new Dictionary<String, String>();
@@ -196,7 +196,7 @@ namespace io.swagger.Api {
     /// <returns></returns>
     public void  deleteOrder (string OrderId) {
       // create path and map variables
-      var path = "/store/order/{orderId}".Replace("{format}","json").Replace("{" + "orderId" + "}", apiInvoker.escapeString(OrderId.ToString()));
+      var path = "/store/order/{orderId}".Replace("{format}","json").Replace("{" + "orderId" + "}", apiInvoker.ParameterToString(OrderId));
 
       // query params
       var queryParams = new Dictionary<String, String>();
diff --git a/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/UserApi.cs b/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/UserApi.cs
index 4f13598da25..c262cbd38cb 100644
--- a/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/src/main/csharp/io/swagger/Api/UserApi.cs
@@ -193,12 +193,10 @@ namespace io.swagger.Api {
       
 
       if (Username != null){
-        string paramStr = (Username is DateTime) ? ((DateTime)(object)Username).ToString("u") : Convert.ToString(Username);
-        queryParams.Add("username", paramStr);
+        queryParams.Add("username", apiInvoker.ParameterToString(Username));
       }
       if (Password != null){
-        string paramStr = (Password is DateTime) ? ((DateTime)(object)Password).ToString("u") : Convert.ToString(Password);
-        queryParams.Add("password", paramStr);
+        queryParams.Add("password", apiInvoker.ParameterToString(Password));
       }
       
 
@@ -291,7 +289,7 @@ namespace io.swagger.Api {
     /// <returns></returns>
     public User  getUserByName (string Username) {
       // create path and map variables
-      var path = "/user/{username}".Replace("{format}","json").Replace("{" + "username" + "}", apiInvoker.escapeString(Username.ToString()));
+      var path = "/user/{username}".Replace("{format}","json").Replace("{" + "username" + "}", apiInvoker.ParameterToString(Username));
 
       // query params
       var queryParams = new Dictionary<String, String>();
@@ -345,7 +343,7 @@ namespace io.swagger.Api {
     /// <returns></returns>
     public void  updateUser (string Username, User Body) {
       // create path and map variables
-      var path = "/user/{username}".Replace("{format}","json").Replace("{" + "username" + "}", apiInvoker.escapeString(Username.ToString()));
+      var path = "/user/{username}".Replace("{format}","json").Replace("{" + "username" + "}", apiInvoker.ParameterToString(Username));
 
       // query params
       var queryParams = new Dictionary<String, String>();
@@ -393,7 +391,7 @@ namespace io.swagger.Api {
     /// <returns></returns>
     public void  deleteUser (string Username) {
       // create path and map variables
-      var path = "/user/{username}".Replace("{format}","json").Replace("{" + "username" + "}", apiInvoker.escapeString(Username.ToString()));
+      var path = "/user/{username}".Replace("{format}","json").Replace("{" + "username" + "}", apiInvoker.ParameterToString(Username));
 
       // query params
       var queryParams = new Dictionary<String, String>();
diff --git a/samples/client/petstore/csharp/src/main/csharp/io/swagger/client/ApiInvoker.cs b/samples/client/petstore/csharp/src/main/csharp/io/swagger/client/ApiInvoker.cs
index 736b51b81f9..c14d1af7d6c 100644
--- a/samples/client/petstore/csharp/src/main/csharp/io/swagger/client/ApiInvoker.cs
+++ b/samples/client/petstore/csharp/src/main/csharp/io/swagger/client/ApiInvoker.cs
@@ -23,6 +23,16 @@
         return str;
       }
 
+      /// <summary>
+      /// if parameter is DateTime, output in ISO8601 format, otherwise just return the string
+      /// </summary>
+      /// <param name="obj"> The parameter (header, path, query, form)
+      /// <returns></returns>
+      public string ParameterToString(object obj)
+      {
+        return (obj is DateTime) ? ((DateTime)obj).ToString ("u") : Convert.ToString (obj);
+      }
+
       public static object deserialize(string json, Type type) {
         try
         {