diff --git a/modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/CSharpClientCodegen.java b/modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/CSharpClientCodegen.java
index 6f5140495c1d..674c842e4093 100644
--- a/modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/CSharpClientCodegen.java
+++ b/modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/CSharpClientCodegen.java
@@ -69,7 +69,7 @@ public class CSharpClientCodegen extends DefaultCodegen implements CodegenConfig
         typeMapping.put("number", "double?");
         typeMapping.put("datetime", "DateTime?");
         typeMapping.put("date", "DateTime?");
-        typeMapping.put("file", "String");
+        typeMapping.put("file", "Stream");
         typeMapping.put("array", "List");
         typeMapping.put("list", "List");
         typeMapping.put("map", "Dictionary");
diff --git a/modules/swagger-codegen/src/main/resources/csharp/ApiClient.mustache b/modules/swagger-codegen/src/main/resources/csharp/ApiClient.mustache
index 0ae71bda25c0..870bf8495618 100644
--- a/modules/swagger-codegen/src/main/resources/csharp/ApiClient.mustache
+++ b/modules/swagger-codegen/src/main/resources/csharp/ApiClient.mustache
@@ -39,7 +39,7 @@ namespace {{packageName}}.Client {
     private Dictionary<String, String> defaultHeaderMap = new Dictionary<String, String>();
 
     public Object CallApi(String Path, RestSharp.Method Method, Dictionary<String, String> QueryParams, String PostBody,
-      Dictionary<String, String> HeaderParams, Dictionary<String, String> FormParams, Dictionary<String, String> FileParams, String[] AuthSettings) {
+      Dictionary<String, String> HeaderParams, Dictionary<String, String> FormParams, Dictionary<String, FileParameter> FileParams, String[] AuthSettings) {
       var response = Task.Run(async () => {
                             var resp = await CallApiAsync(Path, Method, QueryParams, PostBody, HeaderParams, FormParams, FileParams, AuthSettings);
                             return resp;
@@ -48,7 +48,7 @@ namespace {{packageName}}.Client {
     }
 
     public async Task<Object> CallApiAsync(String Path, RestSharp.Method Method, Dictionary<String, String> QueryParams, String PostBody,
-      Dictionary<String, String> HeaderParams, Dictionary<String, String> FormParams, Dictionary<String, String> FileParams, String[] AuthSettings) {
+      Dictionary<String, String> HeaderParams, Dictionary<String, String> FormParams, Dictionary<String, FileParameter> FileParams, String[] AuthSettings) {
 
       var request = new RestRequest(Path, Method);
 
@@ -71,8 +71,9 @@ namespace {{packageName}}.Client {
         request.AddParameter(param.Key, param.Value);
 
       // add file parameter, if any
-      foreach(KeyValuePair<string, string> param in FileParams)
-        request.AddFile(param.Key, param.Value);
+      foreach(KeyValuePair<string, FileParameter> param in FileParams)
+        request.AddFile(param.Value.Name, param.Value.Writer, param.Value.FileName, param.Value.ContentType);
+
 
       if (PostBody != null) {
         request.AddParameter("application/json", PostBody, ParameterType.RequestBody); // http body (model) parameter
@@ -109,6 +110,21 @@ namespace {{packageName}}.Client {
       return str;
     }
 
+    /// <summary>
+    /// Create FileParameter based on Stream
+    /// </summary>
+    /// <param name="name"> parameter name</param>
+    /// <param name="stream">Stream</param>
+    /// <returns>FileParameter</returns>
+    public FileParameter ParameterToFile(string name, Stream stream)
+    {
+        if (stream is FileStream) {
+            return FileParameter.Create(name, StreamToByteArray(stream), ((FileStream)stream).Name);
+        } else {
+            return FileParameter.Create(name, StreamToByteArray(stream), "temp_name_here");
+        }
+    }
+
     /// <summary>
     /// if parameter is DateTime, output in ISO8601 format
     /// if parameter is a list of string, join the list with ","
@@ -136,10 +152,8 @@ namespace {{packageName}}.Client {
     public object Deserialize(string content, Type type, IList<Parameter> headers=null) {
       if (type.GetType() == typeof(Object)) { // return an object
           return (Object)content;
-      } else if (type.Name == "FileStream") { // return a file (full path)
-          // e.g. Content-Disposition: attachment; filename=checkimage.jpp
-          String fileName;
-          String filePath;
+      } else if (type.Name == "Stream") { 
+          String fileName, filePath;
           if (String.IsNullOrEmpty (Configuration.TempFolderPath)) {
               filePath = System.IO.Path.GetTempPath ();
           } else {
@@ -154,8 +168,8 @@ namespace {{packageName}}.Client {
           } else {
               fileName = filePath + Guid.NewGuid().ToString();
           }
-          System.IO.File.WriteAllText (fileName, content);
-          return fileName;
+          File.WriteAllText (fileName, content);
+          return new FileStream(fileName, FileMode.Open);
       } else if (type.Name.StartsWith("System.Nullable`1[[System.DateTime")) { // return a datetime object
           return DateTime.Parse(content,  null, System.Globalization.DateTimeStyles.RoundtripKind);
       } else if (type.Name == "String" || type.Name.StartsWith("System.Nullable")) { // return primitive 
@@ -231,6 +245,26 @@ namespace {{packageName}}.Client {
 
     }
 
+    /// <summary>
+    /// convert a stream to byte array (byte[])
+    /// Ref: http://stackoverflow.com/questions/221925/creating-a-byte-array-from-a-stream
+    /// </summary>
+    /// <param name="input">input stream</param>
+    /// <return>Array of Byte</return>
+    public byte[] StreamToByteArray(Stream input)
+    {
+        byte[] buffer = new byte[16*1024];
+        using (MemoryStream ms = new MemoryStream())
+        {
+            int read;
+            while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
+            {
+                ms.Write(buffer, 0, read);
+            }
+            return ms.ToArray();
+        }
+    }
+
     /// <summary>
     /// Encode string in base64 format 
     /// </summary>
diff --git a/modules/swagger-codegen/src/main/resources/csharp/api.mustache b/modules/swagger-codegen/src/main/resources/csharp/api.mustache
index 7092f66a60c5..3ede1c783a19 100644
--- a/modules/swagger-codegen/src/main/resources/csharp/api.mustache
+++ b/modules/swagger-codegen/src/main/resources/csharp/api.mustache
@@ -100,14 +100,14 @@ namespace {{packageName}}.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       {{#queryParams}} if ({{paramName}} != null) queryParams.Add("{{baseName}}", ApiClient.ParameterToString({{paramName}})); // query parameter
       {{/queryParams}}
       {{#headerParams}} if ({{paramName}} != null) headerParams.Add("{{baseName}}", ApiClient.ParameterToString({{paramName}})); // header parameter
       {{/headerParams}}
-      {{#formParams}}if ({{paramName}} != null) {{#isFile}}fileParams.Add("{{baseName}}", ApiClient.ParameterToString({{paramName}}));{{/isFile}}{{^isFile}}formParams.Add("{{baseName}}", ApiClient.ParameterToString({{paramName}})); // form parameter{{/isFile}}
+      {{#formParams}}if ({{paramName}} != null) {{#isFile}}fileParams.Add("{{baseName}}", ApiClient.ParameterToFile("{{baseName}}", {{paramName}}));{{/isFile}}{{^isFile}}formParams.Add("{{baseName}}", ApiClient.ParameterToString({{paramName}})); // form parameter{{/isFile}}
       {{/formParams}}
       {{#bodyParam}}postBody = ApiClient.Serialize({{paramName}}); // http body (model) parameter
       {{/bodyParam}}
@@ -122,10 +122,7 @@ namespace {{packageName}}.Api {
         throw new ApiException ((int)response.StatusCode, "Error calling {{nickname}}: " + response.Content, response.Content);
       }
 
-      {{#returnType}} // if return type is "String" (not "string"), it implies a Filestream and should return the file path
-      String returnTypeString = "{{{returnType}}}";
-      Type returnType = returnTypeString == "String" ? typeof(FileStream) : typeof({{{returnType}}});
-      return ({{{returnType}}}) ApiClient.Deserialize(response.Content, returnType, response.Headers);{{/returnType}}{{^returnType}}return;{{/returnType}}
+      {{#returnType}}return ({{{returnType}}}) ApiClient.Deserialize(response.Content, typeof({{{returnType}}}), response.Headers);{{/returnType}}{{^returnType}}return;{{/returnType}}
     }
 
     /// <summary>
@@ -148,14 +145,14 @@ namespace {{packageName}}.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       {{#queryParams}} if ({{paramName}} != null) queryParams.Add("{{baseName}}", ApiClient.ParameterToString({{paramName}})); // query parameter
       {{/queryParams}}
       {{#headerParams}} if ({{paramName}} != null) headerParams.Add("{{baseName}}", ApiClient.ParameterToString({{paramName}})); // header parameter
       {{/headerParams}}
-      {{#formParams}}if ({{paramName}} != null) {{#isFile}}fileParams.Add("{{baseName}}", ApiClient.ParameterToString({{paramName}}));{{/isFile}}{{^isFile}}formParams.Add("{{baseName}}", ApiClient.ParameterToString({{paramName}})); // form parameter{{/isFile}}
+      {{#formParams}}if ({{paramName}} != null) {{#isFile}}fileParams.Add("{{baseName}}", ApiClient.ParameterToFile("{{baseName}}", {{paramName}}));{{/isFile}}{{^isFile}}formParams.Add("{{baseName}}", ApiClient.ParameterToString({{paramName}})); // form parameter{{/isFile}}
       {{/formParams}}
       {{#bodyParam}}postBody = ApiClient.Serialize({{paramName}}); // http body (model) parameter
       {{/bodyParam}}
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/PetApi.cs b/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/PetApi.cs
index 2974cb6932b5..96f6f93af57a 100644
--- a/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/PetApi.cs
@@ -122,7 +122,7 @@ namespace IO.Swagger.Api {
     /// <param name="additionalMetadata">Additional data to pass to server</param>
     /// <param name="file">file to upload</param>
     
-    void UploadFile (long? petId, string additionalMetadata, String file);
+    void UploadFile (long? petId, string additionalMetadata, Stream file);
 
     /// <summary>
     /// uploads an image 
@@ -131,7 +131,7 @@ namespace IO.Swagger.Api {
     /// <param name="additionalMetadata">Additional data to pass to server</param>
     /// <param name="file">file to upload</param>
     
-    Task UploadFileAsync (long? petId, string additionalMetadata, String file);
+    Task UploadFileAsync (long? petId, string additionalMetadata, Stream file);
     
   }
 
@@ -202,7 +202,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -240,7 +240,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -277,7 +277,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -315,7 +315,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -352,7 +352,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
        if (status != null) queryParams.Add("status", ApiClient.ParameterToString(status)); // query parameter
@@ -371,10 +371,7 @@ namespace IO.Swagger.Api {
         throw new ApiException ((int)response.StatusCode, "Error calling FindPetsByStatus: " + response.Content, response.Content);
       }
 
-       // if return type is "String" (not "string"), it implies a Filestream and should return the file path
-      String returnTypeString = "List<Pet>";
-      Type returnType = returnTypeString == "String" ? typeof(FileStream) : typeof(List<Pet>);
-      return (List<Pet>) ApiClient.Deserialize(response.Content, returnType, response.Headers);
+      return (List<Pet>) ApiClient.Deserialize(response.Content, typeof(List<Pet>), response.Headers);
     }
 
     /// <summary>
@@ -393,7 +390,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
        if (status != null) queryParams.Add("status", ApiClient.ParameterToString(status)); // query parameter
@@ -429,7 +426,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
        if (tags != null) queryParams.Add("tags", ApiClient.ParameterToString(tags)); // query parameter
@@ -448,10 +445,7 @@ namespace IO.Swagger.Api {
         throw new ApiException ((int)response.StatusCode, "Error calling FindPetsByTags: " + response.Content, response.Content);
       }
 
-       // if return type is "String" (not "string"), it implies a Filestream and should return the file path
-      String returnTypeString = "List<Pet>";
-      Type returnType = returnTypeString == "String" ? typeof(FileStream) : typeof(List<Pet>);
-      return (List<Pet>) ApiClient.Deserialize(response.Content, returnType, response.Headers);
+      return (List<Pet>) ApiClient.Deserialize(response.Content, typeof(List<Pet>), response.Headers);
     }
 
     /// <summary>
@@ -470,7 +464,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
        if (tags != null) queryParams.Add("tags", ApiClient.ParameterToString(tags)); // query parameter
@@ -510,7 +504,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -528,10 +522,7 @@ namespace IO.Swagger.Api {
         throw new ApiException ((int)response.StatusCode, "Error calling GetPetById: " + response.Content, response.Content);
       }
 
-       // if return type is "String" (not "string"), it implies a Filestream and should return the file path
-      String returnTypeString = "Pet";
-      Type returnType = returnTypeString == "String" ? typeof(FileStream) : typeof(Pet);
-      return (Pet) ApiClient.Deserialize(response.Content, returnType, response.Headers);
+      return (Pet) ApiClient.Deserialize(response.Content, typeof(Pet), response.Headers);
     }
 
     /// <summary>
@@ -554,7 +545,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -595,7 +586,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -640,7 +631,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -683,7 +674,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -726,7 +717,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -754,7 +745,7 @@ namespace IO.Swagger.Api {
     /// <param name="additionalMetadata">Additional data to pass to server</param>
     /// <param name="file">file to upload</param>
     
-    public void UploadFile (long? petId, string additionalMetadata, String file) {
+    public void UploadFile (long? petId, string additionalMetadata, Stream file) {
 
       
       // verify the required parameter 'petId' is set
@@ -769,13 +760,13 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
       
       if (additionalMetadata != null) formParams.Add("additionalMetadata", ApiClient.ParameterToString(additionalMetadata)); // form parameter
-      if (file != null) fileParams.Add("file", ApiClient.ParameterToString(file));
+      if (file != null) fileParams.Add("file", ApiClient.ParameterToFile("file", file));
       
       
 
@@ -799,7 +790,7 @@ namespace IO.Swagger.Api {
     /// <param name="additionalMetadata">Additional data to pass to server</param>
     /// <param name="file">file to upload</param>
     
-    public async Task UploadFileAsync (long? petId, string additionalMetadata, String file) {
+    public async Task UploadFileAsync (long? petId, string additionalMetadata, Stream file) {
 
       
           // verify the required parameter 'petId' is set
@@ -814,13 +805,13 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
       
       if (additionalMetadata != null) formParams.Add("additionalMetadata", ApiClient.ParameterToString(additionalMetadata)); // form parameter
-      if (file != null) fileParams.Add("file", ApiClient.ParameterToString(file));
+      if (file != null) fileParams.Add("file", ApiClient.ParameterToFile("file", file));
       
       
 
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/StoreApi.cs b/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/StoreApi.cs
index 14188799013e..90ec2487d9d3 100644
--- a/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/StoreApi.cs
@@ -133,7 +133,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -151,10 +151,7 @@ namespace IO.Swagger.Api {
         throw new ApiException ((int)response.StatusCode, "Error calling GetInventory: " + response.Content, response.Content);
       }
 
-       // if return type is "String" (not "string"), it implies a Filestream and should return the file path
-      String returnTypeString = "Dictionary<String, int?>";
-      Type returnType = returnTypeString == "String" ? typeof(FileStream) : typeof(Dictionary<String, int?>);
-      return (Dictionary<String, int?>) ApiClient.Deserialize(response.Content, returnType, response.Headers);
+      return (Dictionary<String, int?>) ApiClient.Deserialize(response.Content, typeof(Dictionary<String, int?>), response.Headers);
     }
 
     /// <summary>
@@ -172,7 +169,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -207,7 +204,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -226,10 +223,7 @@ namespace IO.Swagger.Api {
         throw new ApiException ((int)response.StatusCode, "Error calling PlaceOrder: " + response.Content, response.Content);
       }
 
-       // if return type is "String" (not "string"), it implies a Filestream and should return the file path
-      String returnTypeString = "Order";
-      Type returnType = returnTypeString == "String" ? typeof(FileStream) : typeof(Order);
-      return (Order) ApiClient.Deserialize(response.Content, returnType, response.Headers);
+      return (Order) ApiClient.Deserialize(response.Content, typeof(Order), response.Headers);
     }
 
     /// <summary>
@@ -248,7 +242,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -288,7 +282,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -306,10 +300,7 @@ namespace IO.Swagger.Api {
         throw new ApiException ((int)response.StatusCode, "Error calling GetOrderById: " + response.Content, response.Content);
       }
 
-       // if return type is "String" (not "string"), it implies a Filestream and should return the file path
-      String returnTypeString = "Order";
-      Type returnType = returnTypeString == "String" ? typeof(FileStream) : typeof(Order);
-      return (Order) ApiClient.Deserialize(response.Content, returnType, response.Headers);
+      return (Order) ApiClient.Deserialize(response.Content, typeof(Order), response.Headers);
     }
 
     /// <summary>
@@ -332,7 +323,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -371,7 +362,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -412,7 +403,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/UserApi.cs b/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/UserApi.cs
index 86549479e320..0e3ed36c5950 100644
--- a/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/UserApi.cs
@@ -194,7 +194,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -232,7 +232,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -269,7 +269,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -307,7 +307,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -344,7 +344,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -382,7 +382,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -420,7 +420,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
        if (username != null) queryParams.Add("username", ApiClient.ParameterToString(username)); // query parameter
@@ -440,10 +440,7 @@ namespace IO.Swagger.Api {
         throw new ApiException ((int)response.StatusCode, "Error calling LoginUser: " + response.Content, response.Content);
       }
 
-       // if return type is "String" (not "string"), it implies a Filestream and should return the file path
-      String returnTypeString = "string";
-      Type returnType = returnTypeString == "String" ? typeof(FileStream) : typeof(string);
-      return (string) ApiClient.Deserialize(response.Content, returnType, response.Headers);
+      return (string) ApiClient.Deserialize(response.Content, typeof(string), response.Headers);
     }
 
     /// <summary>
@@ -463,7 +460,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
        if (username != null) queryParams.Add("username", ApiClient.ParameterToString(username)); // query parameter
@@ -499,7 +496,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -535,7 +532,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -575,7 +572,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -593,10 +590,7 @@ namespace IO.Swagger.Api {
         throw new ApiException ((int)response.StatusCode, "Error calling GetUserByName: " + response.Content, response.Content);
       }
 
-       // if return type is "String" (not "string"), it implies a Filestream and should return the file path
-      String returnTypeString = "User";
-      Type returnType = returnTypeString == "String" ? typeof(FileStream) : typeof(User);
-      return (User) ApiClient.Deserialize(response.Content, returnType, response.Headers);
+      return (User) ApiClient.Deserialize(response.Content, typeof(User), response.Headers);
     }
 
     /// <summary>
@@ -619,7 +613,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -659,7 +653,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -702,7 +696,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -743,7 +737,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
@@ -784,7 +778,7 @@ namespace IO.Swagger.Api {
       var queryParams = new Dictionary<String, String>();
       var headerParams = new Dictionary<String, String>();
       var formParams = new Dictionary<String, String>();
-      var fileParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, FileParameter>();
       String postBody = null;
 
       
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Client/ApiClient.cs b/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Client/ApiClient.cs
index a6b5c3a91da9..04228fad38c4 100644
--- a/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Client/ApiClient.cs
+++ b/samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Client/ApiClient.cs
@@ -39,7 +39,7 @@ namespace IO.Swagger.Client {
     private Dictionary<String, String> defaultHeaderMap = new Dictionary<String, String>();
 
     public Object CallApi(String Path, RestSharp.Method Method, Dictionary<String, String> QueryParams, String PostBody,
-      Dictionary<String, String> HeaderParams, Dictionary<String, String> FormParams, Dictionary<String, String> FileParams, String[] AuthSettings) {
+      Dictionary<String, String> HeaderParams, Dictionary<String, String> FormParams, Dictionary<String, FileParameter> FileParams, String[] AuthSettings) {
       var response = Task.Run(async () => {
                             var resp = await CallApiAsync(Path, Method, QueryParams, PostBody, HeaderParams, FormParams, FileParams, AuthSettings);
                             return resp;
@@ -48,7 +48,7 @@ namespace IO.Swagger.Client {
     }
 
     public async Task<Object> CallApiAsync(String Path, RestSharp.Method Method, Dictionary<String, String> QueryParams, String PostBody,
-      Dictionary<String, String> HeaderParams, Dictionary<String, String> FormParams, Dictionary<String, String> FileParams, String[] AuthSettings) {
+      Dictionary<String, String> HeaderParams, Dictionary<String, String> FormParams, Dictionary<String, FileParameter> FileParams, String[] AuthSettings) {
 
       var request = new RestRequest(Path, Method);
 
@@ -71,8 +71,9 @@ namespace IO.Swagger.Client {
         request.AddParameter(param.Key, param.Value);
 
       // add file parameter, if any
-      foreach(KeyValuePair<string, string> param in FileParams)
-        request.AddFile(param.Key, param.Value);
+      foreach(KeyValuePair<string, FileParameter> param in FileParams)
+        request.AddFile(param.Value.Name, param.Value.Writer, param.Value.FileName, param.Value.ContentType);
+
 
       if (PostBody != null) {
         request.AddParameter("application/json", PostBody, ParameterType.RequestBody); // http body (model) parameter
@@ -109,6 +110,21 @@ namespace IO.Swagger.Client {
       return str;
     }
 
+    /// <summary>
+    /// Create FileParameter based on Stream
+    /// </summary>
+    /// <param name="name"> parameter name</param>
+    /// <param name="stream">Stream</param>
+    /// <returns>FileParameter</returns>
+    public FileParameter ParameterToFile(string name, Stream stream)
+    {
+        if (stream is FileStream) {
+            return FileParameter.Create(name, StreamToByteArray(stream), ((FileStream)stream).Name);
+        } else {
+            return FileParameter.Create(name, StreamToByteArray(stream), "temp_name_here");
+        }
+    }
+
     /// <summary>
     /// if parameter is DateTime, output in ISO8601 format
     /// if parameter is a list of string, join the list with ","
@@ -136,10 +152,8 @@ namespace IO.Swagger.Client {
     public object Deserialize(string content, Type type, IList<Parameter> headers=null) {
       if (type.GetType() == typeof(Object)) { // return an object
           return (Object)content;
-      } else if (type.Name == "FileStream") { // return a file (full path)
-          // e.g. Content-Disposition: attachment; filename=checkimage.jpp
-          String fileName;
-          String filePath;
+      } else if (type.Name == "Stream") { 
+          String fileName, filePath;
           if (String.IsNullOrEmpty (Configuration.TempFolderPath)) {
               filePath = System.IO.Path.GetTempPath ();
           } else {
@@ -154,8 +168,8 @@ namespace IO.Swagger.Client {
           } else {
               fileName = filePath + Guid.NewGuid().ToString();
           }
-          System.IO.File.WriteAllText (fileName, content);
-          return fileName;
+          File.WriteAllText (fileName, content);
+          return new FileStream(fileName, FileMode.Open);
       } else if (type.Name.StartsWith("System.Nullable`1[[System.DateTime")) { // return a datetime object
           return DateTime.Parse(content,  null, System.Globalization.DateTimeStyles.RoundtripKind);
       } else if (type.Name == "String" || type.Name.StartsWith("System.Nullable")) { // return primitive 
@@ -236,6 +250,26 @@ namespace IO.Swagger.Client {
 
     }
 
+    /// <summary>
+    /// convert a stream to byte array (byte[])
+    /// Ref: http://stackoverflow.com/questions/221925/creating-a-byte-array-from-a-stream
+    /// </summary>
+    /// <param name="input">input stream</param>
+    /// <return>Array of Byte</return>
+    public byte[] StreamToByteArray(Stream input)
+    {
+        byte[] buffer = new byte[16*1024];
+        using (MemoryStream ms = new MemoryStream())
+        {
+            int read;
+            while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
+            {
+                ms.Write(buffer, 0, read);
+            }
+            return ms.ToArray();
+        }
+    }
+
     /// <summary>
     /// Encode string in base64 format 
     /// </summary>
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/SwaggerClientTest.userprefs b/samples/client/petstore/csharp/SwaggerClientTest/SwaggerClientTest.userprefs
index 3bc490c9a585..1c38cae6799f 100644
--- a/samples/client/petstore/csharp/SwaggerClientTest/SwaggerClientTest.userprefs
+++ b/samples/client/petstore/csharp/SwaggerClientTest/SwaggerClientTest.userprefs
@@ -1,10 +1,12 @@
 <Properties StartupItem="SwaggerClientTest.csproj">
   <MonoDevelop.Ide.Workspace ActiveConfiguration="Debug" />
-  <MonoDevelop.Ide.Workbench ActiveDocument="TestPet.cs">
+  <MonoDevelop.Ide.Workbench ActiveDocument="Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/PetApi.cs">
     <Files>
-      <File FileName="TestPet.cs" Line="123" Column="3" />
-      <File FileName="Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/PetApi.cs" Line="18" Column="25" />
+      <File FileName="TestPet.cs" Line="123" Column="16" />
       <File FileName="Lib/SwaggerClient/src/main/csharp/IO/Swagger/Client/ApiClient.cs" Line="1" Column="1" />
+      <File FileName="Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/StoreApi.cs" Line="1" Column="1" />
+      <File FileName="Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/UserApi.cs" Line="1" Column="1" />
+      <File FileName="Lib/SwaggerClient/src/main/csharp/IO/Swagger/Api/PetApi.cs" Line="1" Column="1" />
     </Files>
   </MonoDevelop.Ide.Workbench>
   <MonoDevelop.Ide.DebuggingService.Breakpoints>
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/TestPet.cs b/samples/client/petstore/csharp/SwaggerClientTest/TestPet.cs
index bc8fe0fb7578..33530cb0b993 100644
--- a/samples/client/petstore/csharp/SwaggerClientTest/TestPet.cs
+++ b/samples/client/petstore/csharp/SwaggerClientTest/TestPet.cs
@@ -119,7 +119,8 @@ namespace SwaggerClient.TestPet
 		{
 			PetApi petApi = new PetApi ();
 			//NOTE: please provide a valid file (full path)
-			petApi.UploadFile(petId, "new form name", "/var/tmp/small.gif");
+			FileStream fileStream = new FileStream("/var/tmp/small.gif", FileMode.Open);
+			petApi.UploadFile(petId, "new form name", fileStream);
 		}
 
 
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/SwaggerClientTest.dll b/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/SwaggerClientTest.dll
index b9ffd217f0c5..b7164e27ba63 100755
Binary files a/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/SwaggerClientTest.dll and b/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/SwaggerClientTest.dll differ
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/SwaggerClientTest.dll.mdb b/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/SwaggerClientTest.dll.mdb
index 2269827753b4..1faa990e2045 100644
Binary files a/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/SwaggerClientTest.dll.mdb and b/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/SwaggerClientTest.dll.mdb differ
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.csproj.FilesWrittenAbsolute.txt b/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.csproj.FilesWrittenAbsolute.txt
index ff57f8c80e39..9afb7990f577 100644
--- a/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.csproj.FilesWrittenAbsolute.txt
+++ b/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.csproj.FilesWrittenAbsolute.txt
@@ -1,8 +1,8 @@
 /Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/.NETFramework,Version=v4.5.AssemblyAttribute.cs
+/Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/nunit.framework.dll
+/Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/Newtonsoft.Json.dll
+/Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/RestSharp.dll
 /Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/SwaggerClientTest.dll.mdb
 /Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/SwaggerClientTest.dll
 /Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.dll
 /Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.dll.mdb
-/Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/nunit.framework.dll
-/Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/Newtonsoft.Json.dll
-/Users/williamcheng/Code/swagger-codegen/samples/client/petstore/csharp/SwaggerClientTest/bin/Debug/RestSharp.dll
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.dll b/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.dll
index b9ffd217f0c5..b7164e27ba63 100755
Binary files a/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.dll and b/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.dll differ
diff --git a/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.dll.mdb b/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.dll.mdb
index 2269827753b4..1faa990e2045 100644
Binary files a/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.dll.mdb and b/samples/client/petstore/csharp/SwaggerClientTest/obj/Debug/SwaggerClientTest.dll.mdb differ