Configuration c = new Configuration();
System.Net.WebProxy webProxy = new System.Net.WebProxy("http://myProxyUrl:80/");
webProxy.Credentials = System.Net.CredentialCache.DefaultCredentials;
c.Proxy = webProxy;

using System.Collections.Generic;
using System.Diagnostics;
using TestIt.Client.Api;
using TestIt.Client.Client;
using TestIt.Client.Model;

namespace Example
{
    public class Example
    {
        public static void Main()
        {

            Configuration config = new Configuration();
            config.BasePath = "Your TMS address";
            config.AddApiKeyPrefix("Authorization","PrivateToken");
            config.AddApiKey("Authorization","Your private token");

            var apiInstance = new AttachmentsApi(config);
            var id = "id_example";  // Guid |

            try
            {
                // Delete attachment file
                apiInstance.ApiV2AttachmentsIdDelete(id);
            }
            catch (ApiException e)
            {
                Debug.Print("Exception when calling AttachmentsApi.ApiV2AttachmentsIdDelete: " + e.Message );
                Debug.Print("Status Code: "+ e.ErrorCode);
                Debug.Print(e.StackTrace);
            }

        }
    }
}