title: TwoCheckout System.ArgumentNullException : Value cannot be null Parameter name: s
body: <p>I'm trying to integrate my code with 2checkout payment SDK available here:
  <a href="https://github.com/2Checkout/2checkout-dotnet" rel="nofollow">https://github.com/2Checkout/2checkout-dotnet</a></p>
  
  <p>This below code throws the following error:</p>
  
  <blockquote>
    <p>System.ArgumentNullException : Value cannot be null. Parameter name: s</p>
  </blockquote>
  
  <pre><code>[Test]
  public void _004_TestSaleStop()
  {
  
      TwoCheckoutConfig.ApiUsername = "username";
      TwoCheckoutConfig.ApiPassword = "password";
      TwoCheckoutConfig.Sandbox = true;
  
  
      try
      {
  
          var ServiceObject = new SaleService();
          var ArgsObject = new SaleStopServiceOptions();
          ArgsObject.sale_id = 9093729066354;
          var result = ServiceObject.Stop(ArgsObject);
          Assert.IsInstanceOf&lt;TwoCheckoutResponse&gt;(result);
      }
      catch (TwoCheckoutException e)
      {
          Assert.IsInstanceOf&lt;TwoCheckoutException&gt;(e);
      }
  }
  </code></pre>
  
  <p>The error is internal to their code, so it's hard to know why this is thrown.</p>
  
  <p>I've seen some articles suggest that the ASP.NET process does not have write permission. So I right-clicked the solution and added "IIS_IUSRS" with all perms. This doesn't help either.</p>
  
  <p>Any help would be greatly appreciated.</p>