One issue I’ve encountered while building Metro-style WinRT apps on Windows 8 is the need to have my app interact with a WCF service running on the same machine.

This is obviously a common scenario for any n-tier or SOA app development. The challenge we face is that WinRT apps are blocked from calling back to localhost (127.0.0.1). The challenge and solution are described here:

http://msdn.microsoft.com/en-us/library/windows/apps/Hh780593.aspx

To find the real application name (moniker) necessary, I wrote a simple command line utility to read the registry:

using System;
using Microsoft.Win32;

namespace WinRtAppList
{
  class Program
  {
    static void Main(string[] args)
    {
      var reg = Registry.
        CurrentUser.OpenSubKey("Software").
        OpenSubKey("Classes").
        OpenSubKey("Local Settings").
        OpenSubKey("Software").
        OpenSubKey("Microsoft").
        OpenSubKey("Windows").
        OpenSubKey("CurrentVersion").
        OpenSubKey("AppContainer").
        OpenSubKey("Mappings");

      var items = reg.GetSubKeyNames();
      string query = null;
      if (args.Length > 0)
        query = args[0].ToLower();

      foreach (var item in items)
      {
        var app = reg.OpenSubKey(item);
        var displayName = app.GetValue("DisplayName").ToString();
        if (string.IsNullOrEmpty(query) || displayName.ToLower().Contains(query))
        {
          Console.WriteLine(app.GetValue("DisplayName"));
          Console.WriteLine("  SID:     " + item);
          Console.WriteLine("  Moniker: " + app.GetValue("Moniker"));
          Console.WriteLine();
        }
      }

      Console.ReadLine();
    }
  }
}

Nothing fancy, but it helps avoid the need to dig around in the registry with regedit just to find the application moniker.