ASP.NET: Seeing What is in the ViewState in ASP.NET Web Forms

Have you ever wondered what is actually encoded in the __VIEWSTATE hidden variable on your WebForms? It’s actually a base64 serialized encoding of a datatype called a Triplet, that has other objects nested within it. I threw together a small class that has a single static method that will write the ViewState to a file. It intends to see the hierarchy. It also deserializes the ViewState into a Triplet object that you can view in the debugger. This code is only for debugging, and should not be left in the shipping application.

Call the method in the Page_Load event of your Web Form, like this:

DebugViewState.SeeViewState(Request.Form["__VIEWSTATE"], @"c:\temp\viewstate.txt");

And include this class in the project:

using System;
using System.Diagnostics;
using System.Web.UI;

public class DebugViewState
{
  // Written by Greg Reddick. http://www.xoc.net
  public static void SeeViewState(string strViewState, string strFilename)
  {
      if (strViewState != null)
      {
          Debug.Listeners.Clear();
          System.IO.File.Delete(strFilename);
          Debug.Listeners.Add(new TextWriterTraceListener(strFilename));
          string strViewStateDecoded =
          (new System.Text.UTF8Encoding()).
          GetString(Convert.FromBase64String(strViewState));
          string[] astrDecoded = strViewStateDecoded.Replace("<", "<\n").Replace(">", "\n>").Replace(";", ";\n").Split('\n');
          Debug.IndentSize = 4;
          foreach (string str in astrDecoded)
              if (str.Length > 0)
                  if (str.EndsWith(@"\<")) Debug.Write(str);
                  else if (str.EndsWith(@"\")) Debug.Write(str);
                  else if (str.EndsWith("<")) { Debug.WriteLine(str); Debug.Indent(); }
                  else if (str.StartsWith(">;") || str.StartsWith(">"))
                  {
                      Debug.Unindent();
                      Debug.WriteLine(str);
                  }
                  else if (str.EndsWith(@"\;"))
                      Debug.Write(str);
                  else
                      Debug.WriteLine(str);
          Debug.Close();
          Debug.Listeners.Clear();

          //Get into the debugger after executing this line to see how .NET looks
          //at
          //the ViewState info. Compare it to the text file produced above.
          Triplet trp = (Triplet)((new LosFormatter()).Deserialize(strViewState));
      }
  }
}