Catch the Sitecore MVC Exceptions before executing an application error - The Global Exception Tentacle to avoid Yellow Pages of Death

GlobalExceptionHandler.Config

<?xml version="1.0"?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
    <pipelines>
      <mvc.exception>
          <!--
            The Global Exception Tentacle to avoid Yellow Pages of Death
            If ShowExceptionsInPageEditor == true -> The system will throw an exception in the PageEditor
            If ShowExceptionsInPreview == true -> The system will throw an exception in preview mode
            If ShowExceptionsInDebugger == true -> The system will throw an exception in debbuger mode
          -->
            <processor type="Custom.Project.Core.Processors.GlobalExceptionHandler, Custom.Project.Core" patch:before="*[@type='Sitecore.Mvc.Pipelines.MvcEvents.Exception.ShowAspNetErrorMessage, Sitecore.Mvc']">
            <ShowExceptionsInPageEditor>true</ShowExceptionsInPageEditor>
            <ShowExceptionsInPreview>false</ShowExceptionsInPreview>
            <ShowExceptionsInDebugger>true</ShowExceptionsInDebugger>
        </processor>
      </mvc.exception>
    </pipelines>
</configuration>

GlobalExceptionHandler.cs

using System;
using System.Linq;
using System.Web;
using System.Web.Configuration;
using System.Web.Mvc;
using Namics.Opensource.Modules.Logger;
using SC = Sitecore;

namespace Custom.Project.Core.Processors
{
    public class GlobalExceptionHandler : Sitecore.Mvc.Pipelines.MvcEvents.Exception.ExceptionProcessor, IExceptionFilter
    {
        /// <summary>
        /// If Property is true -> The system will throw an exception in the PageEditor
        /// </summary>
        public bool ShowExceptionsInPageEditor { get; set; }
        /// <summary>
        /// If Property is true -> The system will throw an exception in preview mode
        /// </summary>
        public bool ShowExceptionsInPreview { get; set; }
        /// <summary>
        /// If Property is true -> The system will throw an exception in debbuger mode
        /// </summary>
        public bool ShowExceptionsInDebugger { get; set; }

        /// <summary>
        /// The HTTP-Response Header to get an exception information to the client
        /// </summary>
        private const string ExceptionHeader = "X-Exception-Code";

        /// <summary>
        /// Raised by mvc.exception pipeline
        /// </summary>
        /// <param name="context">The Sitecore pipeline exception context</param>
        public void OnException(ExceptionContext context)
        {
            Exception ex = context.Exception;

            // I don't like to manage http exceptions if any guys are trying to get the httpContext in some worker threads...
            if (!(ex is HttpException))
            {
                var excp = new SC.Mvc.Pipelines.MvcEvents.Exception.ExceptionArgs(context);
                this.Process(excp);
            }
        }

        /// <summary>
        /// Last handling possibility of MVC exceptions in Sitecore
        /// </summary>
        /// <param name="args">Sitecore pipeline Exception arguments</param>
        public override void Process(SC.Mvc.Pipelines.MvcEvents.Exception.ExceptionArgs args)
        {
            // Generation of an autogen Exception-Code to refer between http response code and exception line in the log-file
            // That's very usefull to search and find an exception between users and DevOps
            string exceptionCode = Guid.NewGuid().ToString();
            HttpContext current = HttpContext.Current;

            // Log the Exception into the Sitecore log. The Class Logger could be ignored. Please use the normal Sitecore Log feature.
            Logger.Warn(string.Format(
                "An Exception occured (({3}) {0} // Request -> {2} : {1}",
                args.ExceptionContext.Exception.Message,
                args.ExceptionContext.HttpContext.Request.Url,
                args.ExceptionContext.HttpContext.Request.HttpMethod,
                exceptionCode),
                args.ExceptionContext.Exception);

            // If occured multiple exceptions, each code would be separated with a "Pipe"
            if (current.Response.Headers.AllKeys.Contains(ExceptionHeader))
            {
                current.Response.Headers[ExceptionHeader] = current.Response.Headers[ExceptionHeader] + " | " +
                                                               exceptionCode;
            }
            else
            {
                current.Response.Headers.Add(ExceptionHeader, exceptionCode);
            }

            // Control to show an Exception or not
            if (ShouldShowError())
            {
                return;
            }

            // No Exception would be raised by the System
            args.ExceptionContext.ExceptionHandled = true;
        }

        /// <summary>
        /// Exception logic
        /// </summary>
        /// <returns></returns>
        protected bool ShouldShowError()
        {
            CustomErrorsMode mode = SC.Configuration.Settings.CustomErrorsMode;

            return mode == CustomErrorsMode.Off // don't forget the build in CustomErrorMode Logic by Sitecore :-)
              || (this.ShowExceptionsInPageEditor && SC.Context.PageMode.IsPageEditor)
              || (this.ShowExceptionsInPreview && SC.Context.PageMode.IsPreview)
              || (this.ShowExceptionsInDebugger && SC.Context.PageMode.IsDebugging);
        }
    }
}