ASP.NET Diagnostic Page to Dump ASP.NET and Environment Configuration

A handy ASPX page that you can just copy on any website and it dumps the Environment settings and common ASP.NET settings to help diagnose various problems.

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Introduction

Sometimes you need to quickly see if your ASP.NET site is running on the correct server, from the correct code location, using the correct .NET runtime, on a correct OS and hardware environment. Especially if you are running on a shared hosting and you do not have access to the server configuration, dumping Environment variables gives you valuable information about the server processor and you can find out whether the hosting company is putting you on a cheap server. Here’s a handy ASPX page that you can just copy on any website and it dumps the Environment settings and common ASP.NET settings to help diagnose various problems.

It dumps all the Environment variables. I have only shown a few on the screenshot. Then it dumps some useful Request properties. Then it has the ASP.NET tracing output which gives very useful content.

The code of the page is very simple:

<%@ Page Language="C#" AutoEventWireup="true" Trace="true" TraceMode="SortByCategory" %>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
  <title>ASP.NET Diagnostic Page</title>
</head>
<body>
  <form id="form1" runat="server">
  
  <h2>Environment Variables</h2>
  <pre>
  <table>  
<%
    var variables = Environment.GetEnvironmentVariables();
    foreach (DictionaryEntry entry in variables)
    {
      Response.Write("<tr><td>");
      Response.Write(entry.Key);
      Response.Write("</td><td>");
      Response.Write(entry.Value);
      Response.Write("</td></tr>");
    }
  %>
  </table>
  </pre>

  <h2>Misc</h2>
  <pre>
  Response.Filter = <%= Request.Filter.ToString() %>
  Request.ApplicationPath = <%= Request.ApplicationPath %>
  Request.PhysicalApplicationPath = <%= Request.PhysicalApplicationPath %>
  Request.PhysicalPath = <%= Request.PhysicalPath %>
  Request.UrlReferrer = <%= Request.UrlReferrer %>
  Request.UserLanguages = <%= string.Join(",", (Request.UserLanguages ?? new string[0])) %>
  </pre>
  
  </form>
</body>
</html>

That’s all in the Dump.aspx. Just drop this page on a website and you are ready to go.

How to Use this Page

You can use this to test many things:

Dump the cookies browser is sending to your website and see if the cookies are correct. Sometimes you get bad cookie injected in browser by some code and it causes your code to fail. Using this page, you can test that.
See if server has the right .NET framework installed.
Verify if the site is running from the correct webserver by looking at the machine name.
Test if load balancer is working. Deploy this page on all your webservers. Then keep refreshing the page. You should see a different machine name being dumped on different page loads.
Check what is in Session and see if there's something incorrect stored in session that might be causing your application to fail. See if Session is being created at all or not.
Test if you are getting right Request Headers.
Set this page as some form's POST page and make a post to this page to see what is getting posted.

These are just some of the ways you can make use of this page to test your webserver, application code, form posts, AJAX calls and so on.