Handle all Custom Errors in Sitecore MVC

Question

I've edited a patched a pipeline using the following bit of code.

<sitecore>
  <pipelines>
    <mvc.exception>
      <processor type="Sitecore.Mvc.Pipelines.MvcEvents.Exception.ShowAspNetErrorMessage, Sitecore.Mvc">
        <patch:attribute name="type">ProjectName.PublicSite.Web.App_Pipelines.ExceptionHandler.ExceptionHandler, ProjectName.PublicSite.Web</patch:attribute>
    </processor>
</mvc.exception>

In addition, I've created the following class to handle things that fall in the mvc.exception pipeline.

namespace ProjectName.PublicSite.Web.App_Pipelines.ExceptionHandler
{
using Sitecore.Mvc.Pipelines.MvcEvents.Exception;
using Sitecore.Diagnostics;
using System.Configuration;
using System.Web.Configuration;

public class ExceptionHandler : ExceptionProcessor
{
    public override void Process(ExceptionArgs args)
    {
        var context = args.ExceptionContext;
        var httpContext = context.HttpContext;
        var exception = context.Exception;

        if (context.ExceptionHandled || httpContext == null || exception == null || !httpContext.IsCustomErrorEnabled)
        {
            return;
        }
        else
        {
            Log.Error(exception.Message, exception);

            httpContext.Server.ClearError();
            string redirect = "/error";
            httpContext.Response.Redirect(redirect, false);
        }
    }
}

}

The problem that I'm having is that this only handles certain exceptions that can occur, as detailed here and here. I'd like to handle other exceptions that can arise. I've tried adding the following code to the Global.asax.cs file.

protected void Application_Error (object sender, EventArgs e)
{
    Sitecore.Diagnostics.Log.Error("This is an error.", sender);
}

However, I'm not able to get it to hit when I throw an exception in the code. My overall goal is to be able to log any exceptions that may occur in the Sitecore logs.

Answer 1

So for Sitecore - a global error handler in the global.asax will not work properly. The better way to do it is to override the code that calls each rendering and handle the errors there.

ExecuteRenderer

With a simple override of ExecuteRenderer we can easily catch all exceptions:

public class ExecuteRenderer : Sitecore.Mvc.Pipelines.Response.RenderRendering.ExecuteRenderer
{
    public override void Process(RenderRenderingArgs args)
    {
        try
        {
            base.Process(args);
        }
        catch (Exception ex)
        {
            args.Cacheable = false;
            // TODO: Log the error here and deal with how you want to display it to the user
            Log.Error(ex.Message, ex, this);
        }
    }
}

Notice that we are setting args.Cacheable = false - that means that this error handler will work nicely with cached renderings too.

To enable it, simply patch the processor in, replacing the existing one:

<?xml version="1.0"?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
    <sitecore>
        <pipelines>
            <mvc.renderRendering>
                <processor type="Sitecore.Mvc.Pipelines.Response.RenderRendering.ExecuteRenderer, Sitecore.Mvc">
                    <patch:attribute name="type">Sitecore.Exception.Handler.Pipelines.Response.RenderRendering.RenderRendering.ExecuteRenderer, Sitecore.Exception.Handler</patch:attribute>
                </processor>
            </mvc.renderRendering>
        </pipelines>
    </sitecore>
</configuration>

Now you have a global error handler, that will trap errors per rendering. This allows the rest of the site to continue to load nicely and just hides the offending rendering.

For more detail and some more ideas, see my original blog post here Sitecore Rendering Exception Handling