Use .NET Assemblies in FiddlerScript

To use a .NET addon (for this example, a C# addon that modifies the user-agent string):

Add References

  1. Close Fiddler.

  2. Save the .NET file (for example, this file called UASimulator.cs):

    using System;
    using System.Windows.Forms;
    using Fiddler;
    
    namespace FiddlerUtility{
    
          public class UASimulator {
                string m_sUAString;
                public UASimulator(string s_UAString){
                      m_sUAString = s_UAString;
                }
    
                public bool OverwriteUA(Session oSession){
                      oSession.oRequest["User-Agent"] = m_sUAString;
                      return true;
                }
          }
    }
    
  3. In a VS command prompt, go to the folder where the .CS file is found.

  4. Enter the command to create a DLL in the VS command prompt. For example:

    csc /target:library /out:c:\UASim.dll UASimulator.cs /reference:"C:\program files\fiddler2\fiddler.exe"
    
  5. In Fiddler, click Tools > Fiddler Options.

  6. Click the Extensions tab.

  7. In the References field, enter the location of the DLL. For example:

    C:\UASim.dll
    

Update Fiddler Rules

Add a rule to Fiddler to update your script. For example:

    import System;
    import System.Windows.Forms;
    import Fiddler;
    import FiddlerUtility;

    class Handlers{

          static var UASim = new UASimulator("Mozilla/12.0");

          static function OnBeforeRequest(oSession:Fiddler.Session){

                UASim.OverwriteUA(oSession);

          }

       static function Main(){

           var today: Date = new Date();      

           FiddlerObject.StatusText = " CustomRules.js was loaded at: " + today;

       }

    }

See Also