diff --git a/modules/swagger-codegen/src/main/resources/csharp/api.mustache b/modules/swagger-codegen/src/main/resources/csharp/api.mustache
index 85af270c213b..2b3f224cfc58 100644
--- a/modules/swagger-codegen/src/main/resources/csharp/api.mustache
+++ b/modules/swagger-codegen/src/main/resources/csharp/api.mustache
@@ -227,7 +227,7 @@ namespace {{packageName}}.Api
             if ({{paramName}} != null) {{#isFile}}localVarFileParams.Add("{{baseName}}", Configuration.ApiClient.ParameterToFile("{{baseName}}", {{paramName}}));{{/isFile}}{{^isFile}}localVarFormParams.Add("{{baseName}}", Configuration.ApiClient.ParameterToString({{paramName}})); // form parameter{{/isFile}}
             {{/formParams}}
             {{#bodyParam}}
-            if ({{paramName}}.GetType() != typeof(byte[]))
+            if ({{paramName}} != null && {{paramName}}.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize({{paramName}}); // http body (model) parameter
             }
@@ -360,7 +360,7 @@ namespace {{packageName}}.Api
             if ({{paramName}} != null) {{#isFile}}localVarFileParams.Add("{{baseName}}", Configuration.ApiClient.ParameterToFile("{{baseName}}", {{paramName}}));{{/isFile}}{{^isFile}}localVarFormParams.Add("{{baseName}}", Configuration.ApiClient.ParameterToString({{paramName}})); // form parameter{{/isFile}}
             {{/formParams}}
             {{#bodyParam}}
-            if ({{paramName}}.GetType() != typeof(byte[]))
+            if ({{paramName}} != null && {{paramName}}.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize({{paramName}}); // http body (model) parameter
             }
diff --git a/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/PetApi.cs b/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/PetApi.cs
index 75d8dd830c7b..ada1bcbed304 100644
--- a/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/PetApi.cs
@@ -512,7 +512,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -597,7 +597,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -1296,7 +1296,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -1381,7 +1381,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
diff --git a/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/StoreApi.cs b/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/StoreApi.cs
index a2c32ea3f7ec..bbe6343ee84c 100644
--- a/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/StoreApi.cs
@@ -737,7 +737,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -815,7 +815,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
diff --git a/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/UserApi.cs b/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/UserApi.cs
index a94b733e44bb..f4b36e47e325 100644
--- a/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Api/UserApi.cs
@@ -494,7 +494,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -571,7 +571,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -647,7 +647,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -724,7 +724,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -800,7 +800,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -877,7 +877,7 @@ namespace IO.Swagger.Api
             // set "format" to json by default
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -1519,7 +1519,7 @@ namespace IO.Swagger.Api
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
             if (username != null) localVarPathParams.Add("username", Configuration.ApiClient.ParameterToString(username)); // path parameter
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }
@@ -1602,7 +1602,7 @@ namespace IO.Swagger.Api
             // e.g. /pet/{petId}.{format} becomes /pet/{petId}.json
             localVarPathParams.Add("format", "json");
             if (username != null) localVarPathParams.Add("username", Configuration.ApiClient.ParameterToString(username)); // path parameter
-            if (body.GetType() != typeof(byte[]))
+            if (body != null && body.GetType() != typeof(byte[]))
             {
                 localVarPostBody = Configuration.ApiClient.Serialize(body); // http body (model) parameter
             }