>If this is a web app, it's running in your web server, not VS. But if you run in debug, VS attaches the debugger to the process.
>
>You could try stopping the IIS application pool. I don't know for sure if that will work as I don't use IIS for development.
>
No, this is not a WEB app. I am actually running tests, e.g. I press F6 to build the application, then I go to the Tests.cs file where I have test like this:

  [TestMethod][TestCategory("Validation")]
      public void V_vpTestValidatePass_AutoSale2()
      {
          String cResult = "0-OK";
          String cInvoke = @"<func>checkandvalidatepass</func><tcwhichkey></tcwhichkey><tcprefix>A</tcprefix>
<tnpassno>10023001</tnpassno><tcoperator>SAM</tcoperator><tcsalespoint>SC9190</tcsalespoint>
<tcphyslocation>SC9190</tcphyslocation><tnnumvals>1</tnnumvals><typrice>0.00</typrice>
<tcReturnType>STR</tcReturnType><tcdptcatitm></tcdptcatitm>";

          cResult = middlewareMain.Invoke(cInvoke);

          String cExpected = "<ERR>0</ERR><STATUSCODE>0</STATUSCODE><MSG>OK  0-0-OK - PASS_NO: 10023001 - WARNINGS: 0 - DCI: CONSIGNMT VOUCHERS  VOUCHERADT - PASSTABLE: ACCESS </MSG>";
          Assert.IsTrue(String.Equals(cResult.Right(100), cExpected.Right(100), StringComparison.OrdinalIgnoreCase)); // Expected has extra 0-0-OK -- need to work on that
      }

I put a cursor on the cResult line and click on 'Debug Test'. While debugging when I find an error, I stop the debugger to fix the offending piece. After that I try to press F6 again and get the error.