Please note: The FiddlerAPI is still under construction, and future releases may require changes to your code.  Thanks for your patience.

Importers and Exporters

Introduction

Fiddler 2.2.9.5 introduced the ISessionImport and ISessionExport interfaces, allowing you to import traffic to Fiddler and export it to other file formats. Fiddler ships with a number of these "transcoders" by default, but you can also write your own using any .NET language.

Prerequisites

Writing extensions for Fiddler2 requires Visual Studio .NET 2005+ or the free .NET Framework v2 command-line compilers.  Fiddler2 loads only .NET CLR v2.0 assemblies; use Visual Studio 2005+ to compile your extension. You should also ensure your project targets AnyCPU to ensure that it works properly with 64bit Fiddler.

You will also need to have the most recent version of Fiddler2 installed in order to develop Fiddler extensions.

Direct Fiddler2 to load your Transcoder assemblies

Fiddler loads extension assembly DLLs from the %ProgramFiles%\Fiddler2\ImportExport\ and %USERPROFILE%\Documents\Fiddler2\ImportExport\ folders.  Install to the %ProgramFiles% location to make your extensions available to all users on the machine, or the %UserProfile% folder to make the extension available only to the current user.

In addition to placing your Transcoder DLLs in the appropriate folder, you must also mark your assembly to indicate the minimum version of Fiddler required for your Assembly to load correctly. 

Set the Fiddler.RequiredVersion attribute in your AssemblyInfo.cs file (or elsewhere in your code), as follows:

using Fiddler;

// Extension requires Fiddler 2.2.9.7+ because that is when the
// ISessionImport and ISessionExport interfaces were finalized.
[assembly: Fiddler.RequiredVersion("2.2.9.7")]

If Fiddler finds a RequiredVersion attribute that indicates a later version of Fiddler is required, the user will be notified that a later version of Fiddler is required to use your extension.  Assemblies which do not contain a RequiredVersion attribute are silently ignored.

Threading, FiddlerCore, and other notes

Currently, the ISessionImporter and ISessionExporter interfaces are called on the MAIN UI thread. This is almost certain to change in the future, so you should ensure that your classes are thread safe and that they do not attempt to directly manipulate the Fiddler UI.

Manipulation of the Fiddler UI is further ill-advised because Fiddler itself may not be loaded; FiddlerCore may be hosting your Importer/Exporter directly. In order to support FiddlerCore, it's advised that you support the Filename key (with string value of a fully-qualified path) in the dictOptions parameter, and consider supporting a Silent key (value as boolean) as well.

The ISessionImporter Interface

Extensions that implement the ISessionImporter interface (which implements the IDisposable interface) are called when the user uses the File > Import menu option.

public interface ISessionImporter : IDisposable
{
   Session[] ImportSessions(string sImportFormat, Dictionary<string, object> dictOptions,
         EventHandler<ProgressCallbackEventArgs> evtProgressNotifications);
}

The method should return an array of Session objects created from the Import of the data.

The dictOptions dictionary may be null, or may contain a set of string-keyed objects. Most importers support specification of a filename like so dictOptions["Filename"] = "C:\\test.file"

The ISessionExporter Interface

Extensions that implement the ISessionExporter interface (which implements the IDisposable interface) are called when the user uses the File > Export menu option.

public interface ISessionExporter : IDisposable
{
    bool ExportSessions(string sExportFormat, Session[] oSessions,
        Dictionary<string, object> dictOptions, EventHandler<ProgressCallbackEventArgs> evtProgressNotifications);
}

The method should return True if the export of the sessions passed via the oSessions parameter is successful.

The dictOptions dictionary may be null, or may contain a set of string-keyed objects. Most importers support specification of a filename like so dictOptions["Filename"] = "C:\\test.file"

The ProgressCallbackEventArgs class

This class is defined by Fiddler and allows you to report on the progress of an import or export operation.

If the completion ratio cannot be determined, simply pass 0 or a "guess" between 0 and 1.0.

If the Cancel flag is set on the ProgressCallbackEventArgs object after being passed to the evtProgressNotifications callback, import or export should gracefully terminate as soon as possible.

public class ProgressCallbackEventArgs: EventArgs
{
  public ProgressCallbackEventArgs(float flCompletionRatio, string sProgressText)
  public string ProgressText { get; }
  public string PercentComplete { get; }
  public bool Cancel { get; set; }
}