Hey Kerem,

Thank you for your patience!

I have tried to reproduce this access issue, although I couldn't. Below you will find a sample that is implementing the exact scenario. I have a WebDataGrid with WebDataMenu which is used as a context menu, and on first item click I call a WebService/GetData WebMethod which is returning a simple string. That string is passed as a content to a DialogWindow.

Could you please have a look at the sample and let me know what I am missing from your scenario. I hope that you will find the sample helpful.

Code snippet:

<script id="igClientScript">
 function GridMouseDown(grid, eventArgs) {
  var menu = $find("<%= this.WebDataMenu1.ClientID %>");
  var targetElement = eventArgs.get_browserEvent().target;
  var selectedRow = grid.get_behaviors().get_selection().get_selectedRows().getItem(0);
  var currentlySelectedRow = eventArgs.get_item().get_row();

  if (eventArgs.get_item() == null || !eventArgs.get_item().get_row) {
   return;
  }

  menu.showAt(null, null, eventArgs.get_browserEvent());
 }

 function getData(sender, eventArgs) {
  if (eventArgs.getItem().get_key() === "miRun") {
   $.ajax({
    type: "POST",
    url: "WebService.asmx/GetData",
    data: "{}",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function (response) {
     var data = response.d;
     var $dialog = $find("wdw1");
     $dialog.show();
     $($dialog.findChild("content")).html(data);
    },
    error: function (response) {
     console.log(response);
    }
   });
  }
 }
</script>

WebService:

[System.Web.Script.Services.ScriptService]
public class WebService : System.Web.Services.WebService {

    public WebService () {

        //Uncomment the following line if using designed components
        //InitializeComponent();
    }
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    [WebMethod]
    public string GetData()
    {
        return "Some data";
    }
}

Looking forward to hearing from you.