Ajax enabled webpart not working on second postback

Trying to develope an Ajax webpart with aspx.net 2.0 I came up with this msdn example  which seemed to be exactly what I was looking for. I followed the steps suggested by the article but I ended up with some weird behaviour from the webpart when finally deployed in my Sharepoint server.

Apparently everything was working as expected and when I clicked the webpart the first time, the ajax method was correctly executed and the “Hello! XXX” text succesfully displayed. However, clicking again the button didn’t seem to do anything, also, other page actions that should submit the form and do some action (like the “Edit Page” item from the “Site Actions” menu) stopped working.

I finally found that the problem was in the EnsurePanelFix function of the example which was not working as expected

private void EnsurePanelFix()
{
   if (this.Page.Form != null)
   {
     String fixupScript = @"
     _spBodyOnLoadFunctionNames.push(""_initFormActionAjax"");
     function _initFormActionAjax()
     {
       if (_spEscapedFormAction == document.forms[0].action)
       {
         document.forms[0]._initialAction =
         document.forms[0].action;
       }
     }
     var RestoreToOriginalFormActionCore =
       RestoreToOriginalFormAction;
     RestoreToOriginalFormAction = function()
     {
       if (_spOriginalFormAction != null)
       {
         RestoreToOriginalFormActionCore();
         document.forms[0]._initialAction =
         document.forms[0].action;
       }
     }";
   ScriptManager.RegisterStartupScript(this,
     typeof(SayHelloWebPart), "UpdatePanelFixup",
     fixupScript, true);
   }
}

So what I did is to provide my own implementation of that function. What we needed is to invalidate the onSubmit wrapper that Sharepoint calls in order to ensure some callback scenarios, this can be done by setting to true the _spSuppressFormOnSubmitWrapper variable so I replaced the original function by the following implementation

private void EnsurePanelFix()
        {
              ScriptManager.RegisterStartupScript
                (this,
                 typeof(AjaxEnabledWebpart),
                 "UpdatePanelFixup",
                 "_spOriginalFormAction = document.forms[0].action; _spSuppressFormOnSubmitWrapper=true;",
                 true);
}

And that’s it ! my Ajax webpart is working properly no matter how many times we click the Hello World ! button 🙂