WebResource.axd (404) not found

Good morning guys!

A few days ago I was working on an ASP.NET web form application which uses the control library Telerik ASP.NET AJAX. The application worked without problems until it was moved in a new server running Windows Server 2019.

Running in the new environment it stopped working and in the browser’s development console I found the following error:

http://192.168.1.179/WebResource.axd?d=e1fJsJFz7dj_REV7goreuE6rTrJgNckVYcNF5QZTQi8D8NPA3ikIkl5P2o3zcgfQZ0QChDOntG2bqXblHn9EATnjjEgqJ1isYAp_gOm_zpEODUi43QJvmDmatf5IjLlmM70Yblyiu0QLk5_Z-62E1FJEZJ-eJPytslEcs9Qh4GazQtbm7eaEku3YlJE5EOBi0&t=9484985410605809954 net::ERR_ABORTED 404 (Not Found)

Searching the internet, I found various reasons that could cause this problem and none of them applied to me. The turning point was reading the IIS log which reported the exact http error code obtained from the request, which in my case was 404.15.

Looking at the meaning of the error code 404.15 (for example here), I found that 404.15 means “query string too long”.

So I solved the problem modifying the web.config of the application adding the following attribute

maxQueryStringLength=”8192″

to the tag httpRuntime.

My situation now looks like this:

<system.web>
    ...
    <httpRuntime ... maxQueryStringLength="8192" />
    ...
</system.web>

Now the application works fine… Note that the value 8192 is suitable for my situation, clearly it can be changed according to your needs.