SSIS - Script task export import variable

  public void Main()

        {

            // TODO: Add your code here

            string str = Dts.Variables["User::Internal_Sales_File_Name"].Value.ToString();

            str = str.Substring(str.Length - 9, 4);

            Dts.Variables["Internal_Sales_Year"].Value = str;

           // string test = Dts.Variables["User::Internal_Sales_Year"].Value.ToString();

       

            Dts.TaskResult = (int)ScriptResults.Success;

        }

    }

}