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copied!<p><strong>UPDATE</strong><br> Since this answer does provide a solution, I will not edit it, but I have found a much cleaner way of solving this problem. See <a href="https://stackoverflow.com/a/9572858/346561">my other answer</a> for details...</p> <p><strong>Original Answer:</strong><br> I figured out why the <code>Application_Error()</code> method is not being invoked...</p> <p><strong>Global.asax.cs</strong></p> <pre><code>public class MvcApplication : System.Web.HttpApplication { public static void RegisterGlobalFilters(GlobalFilterCollection filters) { filters.Add(new HandleErrorAttribute()); // this line is the culprit } ... } </code></pre> <p>By default (when a new project is generated), an MVC application has some logic in the <code>Global.asax.cs</code> file. This logic is used for mapping routes and registering filters. By default, it only registers one filter: a <code>HandleErrorAttribute</code> filter. When customErrors are on (or through remote requests when it is set to RemoteOnly), the HandleErrorAttribute tells MVC to look for an Error view and it never calls the <code>Application_Error()</code> method. I couldn't find documentation of this but it is explained in <a href="https://softwareengineering.stackexchange.com/questions/45195/what-are-the-definitive-guidelines-for-custom-error-handling-in-asp-net-mvc-3/45197#45197">this answer on programmers.stackexchange.com</a>.</p> <p>To get the ApplicationError() method called for <strong>every</strong> unhandled exception, simple remove the line which registers the HandleErrorAttribute filter.</p> <p>Now the problem is: How to configure the customErrors to get what you want...</p> <p>The customErrors section defaults to <code>redirectMode="ResponseRedirect"</code>. You can specify the defaultRedirect attribute to be a MVC route too. I created an ErrorController which was very simple and changed my web.config to look like this...</p> <p><strong>web.config</strong></p> <pre><code><customErrors mode="RemoteOnly" redirectMode="ResponseRedirect" defaultRedirect="~/Error"> <error statusCode="404" redirect="~/Error/PageNotFound" /> </customErrors> </code></pre> <p>The problem with this solution is that it does a 302 redirect to your error URLs and then those pages respond with a 200 status code. This leads to Google indexing the error pages which is bad. It also isn't very conformant to the HTTP spec. What I wanted to do was not redirect, and overrite the original response with my custom error views.</p> <p>I tried to change <code>redirectMode="ResponseRewrite"</code>. Unfortunately, <a href="https://stackoverflow.com/questions/781861/customerrors-does-not-work-when-setting-redirectmode-responserewrite/3770265#3770265">this option does not support MVC routes</a>, only static HTML pages or ASPX. I tried to use an static HTML page at first but the response code was still 200 but, at least it didn't redirect. I then got an idea from <a href="https://softwareengineering.stackexchange.com/questions/45195/what-are-the-definitive-guidelines-for-custom-error-handling-in-asp-net-mvc-3/45197#45197">this answer</a>...</p> <p>I decided to give up on MVC for error handling. I created an <code>Error.aspx</code> and a <code>PageNotFound.aspx</code>. These pages were very simple but they had one piece of magic...</p> <pre><code><script type="text/C#" runat="server"> protected override void OnLoad(EventArgs e) { base.OnLoad(e); Response.StatusCode = (int) System.Net.HttpStatusCode.InternalServerError; } </script> </code></pre> <p>This block tells the page to be served with the correct status code. Of coarse, on the PageNotFound.aspx page, I used <code>HttpStatusCode.NotFound</code> instead. I changed my web.config to look like this...</p> <pre><code><customErrors mode="RemoteOnly" redirectMode="ResponseRewrite" defaultRedirect="~/Error.aspx"> <error statusCode="404" redirect="~/PageNotFound.aspx" /> </customErrors> </code></pre> <p>It all worked perfectly!</p> <p><strong>Summary:</strong></p> <ul> <li>Remove the line: <code>filters.Add(new HandleErrorAttribute());</code></li> <li>Use <code>Application_Error()</code> method to log exceptions</li> <li>Use customErrors with a ResponseRewrite, pointing at ASPX pages</li> <li>Make the ASPX pages responsible for their own response status codes</li> </ul> <p>There are a couple downsides I have noticed with this solution.</p> <ul> <li>The ASPX pages can't share any markup with Razor templates, I had to rewrite our website's standard header and footer markup for a consistent look and feel.</li> <li>The *.aspx pages can be accessed directly by hitting their URLs</li> </ul> <p>There are work-arounds for these problems but I wasn't concerned enough by them to do any extra work.</p> <p>I hope this helps everyone!</p>

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