Question

For a website/ vpath, it’s possible to handle the Application_Error event to catch errors before they get sent back to the browser. Is it possible to also do this at the server level somehow? That is, define a method at the root level that will execute if an error occurs in a website, but that website fails to handle the error for whatever reason.

I know you can use the web.config at the root level to define custom error messages per HTTP status code. However, this isn’t ideal for my case, because I want to return different types of content (ie, HTML or something else) depending on the application logic.

Answer 1

A custom http module can be registered at applicationHost.config. Then this module is used by all IIS applications on the target machine.

1) Create a signed class library project with http module:

public class ErrorHandlingModule : IHttpModule
{
    public void Dispose() { }

    public void Init(HttpApplication context)
    {
        context.Error += new EventHandler(context_Error);
    }

    void context_Error(object sender, EventArgs e)
    {
        // handle error
    }
}

2) Install the class library into GAC, so it can be shared by all IIS applications.

3) Install the http module to applicationHost.config file. This file usualy resides in C:\Windows\System32\inetsrv\config. Files in this folder can be accessed only by 64-bit processes (there is no such issue on 32-bit OSes), VS2010 cannot see them but Explorer can. The applicationHost.config fragment could look like this:

<location path="" overrideMode="Allow">
    <system.webServer>
        <modules>
            <add name="MyModule" preCondition="managedHandler" type="GlobalErrorHandler.ErrorHandlingModule, GlobalErrorHandler, Version=1.0.0.0, Culture=neutral, PublicKeyToken=bfd166351ed997df" />