FiddlerScript C# is an extension for Telerik Fiddler that lets you use C# for scripting instead of the build-in JScript.NET.

FiddlerScript C# is powered by Roslyn Scripting.

#Installation To install, compile the project and copy the contents of the output into ~/Documents/Fiddler2/Scripts.

#Use Create a file with the .crx extension in ~/Documents/Fiddler2/Scripts and begin writing code, that's it. You can create as many scripts in this directory as you would like, however they cannot be guaranteed to run in any particular order. A simple example that alternates the colors of sessions in the user interface:

using Fiddler;

public void OnBeforeRequest(Session oSession)
{
	oSession["ui-color"] = oSession.id % 2 == 0 ? "red" : "green";
}
FiddlerApplication.Log.LogString("Script has been initialized.");

That's all you need in the file. Unlike full C#, Roslyn scripting doesn't require a full class declaration.

#Comparison with JScript.NET Engine Currently the FiddlerScript C# bindings are more limited than the JScript.NET ones, however some of the major features have been implemented.

#Namespaces and assemblies FiddlerScript C# automatically imports the following assemblies:

• mscorlib
• System
• System.Core
• Microsoft.CSharp
• Fiddler

Additional references can be supplied using the #r syntax. For example, at the top of your script:

#r "System.Drawing"
#r "System.Windows.Forms"
using System.Windows.Forms;

Assemblies are searched for in the ~/Documents/Fiddler2/Scripts directory and the installation directory of Fiddler.

By default, the following namespaces are automatically imported:

• System
• Fiddler

#API

###OnBeforeRequest (AutoTamperRequestBefore)

//The "AutoTamperRequestBefore" name is also acceptable
public void OnBeforeRequest(Session session)
{
	//Access the session before the client has sent the request
}

###OnAfterRequest (AutoTamperRequestAfter)

//The "AutoTamperRequestAfter" name is also acceptable
public void OnAfterRequest(Session session)
{
	//Access the session after the request has been sent to the server
}

###OnBeforeResponse (AutoTamperResponseBefore)

//The "AutoTamperResponseBefore" name is also acceptable
public void OnBeforeResponse(Session session)
{
	//Access the session after the request has been sent to the server but
	//before the client has received the response
}

###OnAfterResponse (AutoTamperResponseAfter)

//The "AutoTamperResponseAfter" name is also acceptable
public void OnAfterResponse(Session session)
{
	//Access the session after the client has received the response.
}

###OnPeekAtRequestHeaders

public void OnPeekAtRequestHeaders(Session session)
{
	//Access the request headers before the request body is available
}

###OnPeekAtResponseHeaders

public void OnPeekAtResponseHeaders(Session session)
{
	//Access the response headers before the response body is available
}

###OnReturningError (OnBeforeReturningError)

//The "OnBeforeReturningError" name is also acceptable
public void OnReturningError(Session session)
{
	//Occures when Fiddler itself returns an error during the request / response.
}

###OnBeforeShutdown

public bool OnBeforeShutdown()
{
	//Return false to prevent fiddler from closing
}

###Main

public void Main()
{
	//Executed immediately after the script is loaded.
}

#Globals

FiddlerScript C# supports the same global properties that JScript.NET does.

###UI

Supports the same UI helpers that JScript.NET does, such as:

UI.actRemoveAllSessions();

###FiddlerObject

Supports a subset of helpers that JScript.NET does, currently:

• void alert(string message)
• void utilIssueRequest(string request)
• string prompt(string message, string defaultValue = "FiddlerScript C# Prompt", string windowTitle = "FiddlerScript C# Prompt")
• void playSound(string soundname)
• void log(string sMessage)