ASP.NET Ajax Error: Sys.WebForms.PageRequestManagerParserErrorException

Question

My website has been giving me intermittent errors when trying to perform any Ajax activities. The message I get is

Sys.WebForms.PageRequestManagerP         


        

Answer 1

I solved this same problem by removing mistakenly-nested UpdatePanels.

Answer 2

I finally solved my variant of this same problem. I was attempting to copy/move a selected value between 2 listboxes in a webform. In my case, I had to specifically call {listbox}.ClearSelection() prior performing the action the 2nd time around.

So obviously this problem/error message can occur for a multitude of reasons.

Answer 3

Change of the app pool FROM INTEGRATED to asp.net classic solved the problem for me.

Answer 4

Update the ScriptMode to "Release"

<asp:ScriptManager ID="ScriptManager" runat="server" ScriptMode="Release"></asp:ScriptManager>

Answer 5

Probably there is an error occuring on post back. In this case, you can view the details about the error by adding a PostBackTrigger to your updatepanel and referencing the button which causes the problem:

    <asp:updatepanel ID="updatepanel1" runat="server">
        <Triggers>
            <asp:PostBackTrigger ControlID="button1" /> 
        </Triggers>
        <ContentTemplate>

        </ContentTemplate>
    </asp:updatepanel>

Answer 6

I had this happen to me and none of the causes on the list in the answer applied. I didn't find the root of the problem until I disabled my AJAX altogether. Discovered that the code was saving an object to the ViewState that contained an unserializable object. I made the object serializable and it started working again.