Sys.WebForms.PageRequestManagerServerErrorException 12031

I’m occasionaly getting the following popup from an AJAX.NET application

Sys.WebForms.PageRequestManagerServerErrorException: An Unknown error occurred while processing the request on the server. The status code returned from the server was: 12031

From the Microsoft kb that status code indicates a ERROR_INTERNET_CONNECTION_RESET, but it doesn’t state what was the underlying issue the triggered the error in the first place.

How can I log/trace/etc the underlying error that generated the popup?


Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

If you’re getting that from an updatePanel, set EnablePartialRendering to false in the ScriptManager for the page, and then it should give you the actual error.

Also, if it only happens occasionally, I’ve found that it could be a viewstate problem, especially when the page goes a long time (20mins or so) between refreshes.

Otherwise, try some try/catch blocks. Those are some easy methods.

Hope that helps!

Method 2

It’s a viewstate problem, but not related with time but with size. Try playing with maxRequestLength in your web.config.

Method 3

add <httpRuntime requestValidationMode="2.0"/>
in web.config
and in YourPage.aspx set (ClientIDMode=”Static” ValidateRequest=”false”)


EXAMPLE: web.config

   <?xml version="1.0"?>
  For more information on how to configure your ASP.NET application, please visit
    <httpRuntime requestValidationMode="2.0"/>
    <compilation debug="true" targetFramework="4.0">
        <add assembly="System.Data.Entity, Version=, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>


    <add name="WT_ZadnjiEntities" connectionString="metadata=res://*/DAL.Model.csdl|res://*/DAL.Model.ssdl|res://*/DAL.Model.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=SATELLITE-PC;initial catalog=WT_Zadnji;integrated security=True;multipleactiveresultsets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />

Method 4

I’ve got this error in UpdatePanel with autopostback Dropdown after big delay (>20 min) between change dropdown selection.

Try increase session timeout in web.cofig. For example:

<sessionState mode="InProc" cookieless="true" timeout="720"/>;

Method 5

sometimes the error occurs if you have added a server SSL certificate(https).If the certificate is not valid it will give this error.

Method 6

I had the following error happening on postback:

Error: Sys.WebForms.PageRequestManagerServerErrorException: An unknown error occurred while processing the request on the server.

But for me, the issue was that I am converting my project from ASP.NET 2.0 to ASP.NET 4.0 and I had <asp:UpdatePanel runat="server"> used on the page.

I took off the <asp:UpdatePanel runat="server"> (for the time being), then ran the page to get the exact error. Which was “A potentially dangerous Request.Form value was detected”

I found that even though I have ValidateRequest="false" on the page, ASP.NET 4.0 requires you to add requestValidationMode="2.0" in the HttpRuntime tag of web.config.

<httpRuntime maxRequestLength="102400" requestValidationMode="2.0"/>


All methods was sourced from or, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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