diff --git a/modules/openapi-generator/src/main/resources/csharp/ApiClient.mustache b/modules/openapi-generator/src/main/resources/csharp/ApiClient.mustache
index 91ea70055b06..42805335d39f 100644
--- a/modules/openapi-generator/src/main/resources/csharp/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/ApiClient.mustache
@@ -449,7 +449,7 @@ namespace {{packageName}}.Client
         /// <param name="configuration">A per-request configuration object.
         /// It is assumed that any merge with GlobalConfiguration has been done before calling this method.</param>
         /// <returns>A new ApiResponse instance.</returns>
-        private async Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, Task<RestResponse<T>>> getResponse, Action<RestClientOptions> setOptions, RestRequest request, RequestOptions options, IReadableConfiguration configuration)
+        private async System.Threading.Tasks.Task<ApiResponse<T>> ExecClientAsync<T>(Func<RestClient, System.Threading.Tasks.Task<RestResponse<T>>> getResponse, Action<RestClientOptions> setOptions, RestRequest request, RequestOptions options, IReadableConfiguration configuration)
         {
             var baseUrl = configuration.GetOperationServerUrl(options.Operation, options.OperationIndex) ?? _baseUrl;
             var clientOptions = new RestClientOptions(baseUrl)
@@ -550,7 +550,7 @@ namespace {{packageName}}.Client
             }
         }
 
-        private async Task<RestResponse<T>> DeserializeRestResponseFromPolicyAsync<T>(RestClient client, RestRequest request, PolicyResult<RestResponse> policyResult, CancellationToken cancellationToken = default)
+        private async System.Threading.Tasks.Task<RestResponse<T>> DeserializeRestResponseFromPolicyAsync<T>(RestClient client, RestRequest request, PolicyResult<RestResponse> policyResult, CancellationToken cancellationToken = default)
         {
             if (policyResult.Outcome == OutcomeType.Successful) 
             {
@@ -581,7 +581,7 @@ namespace {{packageName}}.Client
                 clientOptions.CookieContainer = cookies;
             };
 
-            Func<RestClient, Task<RestResponse<T>>> getResponse = (client) =>
+            Func<RestClient, System.Threading.Tasks.Task<RestResponse<T>>> getResponse = (client) =>
             {
                 if (RetryConfiguration.RetryPolicy != null)
                 {
@@ -591,7 +591,7 @@ namespace {{packageName}}.Client
                 }
                 else
                 {
-                    return Task.FromResult(client.Execute<T>(request));
+                    return System.Threading.Tasks.Task.FromResult(client.Execute<T>(request));
                 }
             };
 
@@ -599,14 +599,14 @@ namespace {{packageName}}.Client
         }
 
         {{#supportsAsync}}
-        private Task<ApiResponse<T>> ExecAsync<T>(RestRequest request, RequestOptions options, IReadableConfiguration configuration, CancellationToken cancellationToken = default(CancellationToken))
+        private System.Threading.Tasks.Task<ApiResponse<T>> ExecAsync<T>(RestRequest request, RequestOptions options, IReadableConfiguration configuration, CancellationToken cancellationToken = default(CancellationToken))
         {
             Action<RestClientOptions> setOptions = (clientOptions) =>
             {
                 //no extra options
             };
 
-            Func<RestClient, Task<RestResponse<T>>> getResponse = async (client) =>
+            Func<RestClient, System.Threading.Tasks.Task<RestResponse<T>>> getResponse = async (client) =>
             {
                 {{#supportsRetry}}
                 if (RetryConfiguration.AsyncRetryPolicy != null)
@@ -637,7 +637,7 @@ namespace {{packageName}}.Client
         /// GlobalConfiguration has been done before calling this method.</param>
         /// <param name="cancellationToken">Token that enables callers to cancel the request.</param>
         /// <returns>A Task containing ApiResponse</returns>
-        public Task<ApiResponse<T>> GetAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
+        public System.Threading.Tasks.Task<ApiResponse<T>> GetAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
         {
             var config = configuration ?? GlobalConfiguration.Instance;
             return ExecAsync<T>(NewRequest(HttpMethod.Get, path, options, config), options, config, cancellationToken);
@@ -652,7 +652,7 @@ namespace {{packageName}}.Client
         /// GlobalConfiguration has been done before calling this method.</param>
         /// <param name="cancellationToken">Token that enables callers to cancel the request.</param>
         /// <returns>A Task containing ApiResponse</returns>
-        public Task<ApiResponse<T>> PostAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
+        public System.Threading.Tasks.Task<ApiResponse<T>> PostAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
         {
             var config = configuration ?? GlobalConfiguration.Instance;
             return ExecAsync<T>(NewRequest(HttpMethod.Post, path, options, config), options, config, cancellationToken);
@@ -667,7 +667,7 @@ namespace {{packageName}}.Client
         /// GlobalConfiguration has been done before calling this method.</param>
         /// <param name="cancellationToken">Token that enables callers to cancel the request.</param>
         /// <returns>A Task containing ApiResponse</returns>
-        public Task<ApiResponse<T>> PutAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
+        public System.Threading.Tasks.Task<ApiResponse<T>> PutAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
         {
             var config = configuration ?? GlobalConfiguration.Instance;
             return ExecAsync<T>(NewRequest(HttpMethod.Put, path, options, config), options, config, cancellationToken);
@@ -682,7 +682,7 @@ namespace {{packageName}}.Client
         /// GlobalConfiguration has been done before calling this method.</param>
         /// <param name="cancellationToken">Token that enables callers to cancel the request.</param>
         /// <returns>A Task containing ApiResponse</returns>
-        public Task<ApiResponse<T>> DeleteAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
+        public System.Threading.Tasks.Task<ApiResponse<T>> DeleteAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
         {
             var config = configuration ?? GlobalConfiguration.Instance;
             return ExecAsync<T>(NewRequest(HttpMethod.Delete, path, options, config), options, config, cancellationToken);
@@ -697,7 +697,7 @@ namespace {{packageName}}.Client
         /// GlobalConfiguration has been done before calling this method.</param>
         /// <param name="cancellationToken">Token that enables callers to cancel the request.</param>
         /// <returns>A Task containing ApiResponse</returns>
-        public Task<ApiResponse<T>> HeadAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
+        public System.Threading.Tasks.Task<ApiResponse<T>> HeadAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
         {
             var config = configuration ?? GlobalConfiguration.Instance;
             return ExecAsync<T>(NewRequest(HttpMethod.Head, path, options, config), options, config, cancellationToken);
@@ -712,7 +712,7 @@ namespace {{packageName}}.Client
         /// GlobalConfiguration has been done before calling this method.</param>
         /// <param name="cancellationToken">Token that enables callers to cancel the request.</param>
         /// <returns>A Task containing ApiResponse</returns>
-        public Task<ApiResponse<T>> OptionsAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
+        public System.Threading.Tasks.Task<ApiResponse<T>> OptionsAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
         {
             var config = configuration ?? GlobalConfiguration.Instance;
             return ExecAsync<T>(NewRequest(HttpMethod.Options, path, options, config), options, config, cancellationToken);
@@ -727,7 +727,7 @@ namespace {{packageName}}.Client
         /// GlobalConfiguration has been done before calling this method.</param>
         /// <param name="cancellationToken">Token that enables callers to cancel the request.</param>
         /// <returns>A Task containing ApiResponse</returns>
-        public Task<ApiResponse<T>> PatchAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
+        public System.Threading.Tasks.Task<ApiResponse<T>> PatchAsync<T>(string path, RequestOptions options, IReadableConfiguration configuration = null, CancellationToken cancellationToken = default)
         {
             var config = configuration ?? GlobalConfiguration.Instance;
             return ExecAsync<T>(NewRequest(HttpMethod.Patch, path, options, config), options, config, cancellationToken);