Registering a protocol handler in Windows 8

You were on the right track with the Default Programs web page - in fact, it's my reference for this post.

The following adapts their example:

First, you need a ProgID in HKLM\SOFTWARE\Classes that dictates how to handle any input given to it (yours may already exist):

HKLM\SOFTWARE\Classes     MyApp.ProtocolHandler //this is the ProgID, subkeys are its properties        (Default) = My Protocol //name of any type passed to this        DefaultIcon           (Default) = %ProgramFiles%\MyApp\MyApp.exe, 0 //for example        shell           open              command                 (Default) = %ProgramFiles%\MyApp\MyApp.exe %1 //for example

Then fill the registry with DefaultProgram info inside a Capabilities key:

HKLM\SOFTWARE\MyApp    Capabilities       ApplicationDescription           URLAssociations              myprotocol = MyApp.ProtocolHandler //Associated with your ProgID

Finally, register your application's capabilities with DefaultPrograms:

HKLM\SOFTWARE      RegisteredApplications         MyApplication = HKLM\SOFTWARE\MyApp\Capabilities

Now all "myprotocol:" links should trigger %ProgramFiles%\MyApp\MyApp.exe %1.

Side note since this is a top answer found when googling this kind of an issue: Make sure the path in the shell command open is a proper path to your application. I spent an entire day debugging issue that seemed only to affect Chrome and Edge on Windows 10. They never triggered the protocol handler while Firefox did.What was the issue? The path to the .bat file used mixed \ and / slashes.Using only proper \ slashes in the path made Edge & Chrome suddenly able to pick up the request.

LaunchUriAsync(Uri)

Starts the default app associated with the URI scheme name for the specified URI. You can allow the user to specify, in this case.

http://msdn.microsoft.com/library/windows/apps/Hh701476

    // Create the URI to launch from a string.    var uri = new Uri(uriToLaunch);    // Calulcate the position for the Open With dialog.    // An alternative to using the point is to set the rect of the UI element that triggered the launch.    Point openWithPosition = GetOpenWithPosition(LaunchUriOpenWithButton);    // Next, configure the Open With dialog.    // Here is where you choose the program.    var options = new Windows.System.LauncherOptions();    options.DisplayApplicationPicker = true;    options.UI.InvocationPoint = openWithPosition;    options.UI.PreferredPlacement = Windows.UI.Popups.Placement.Below;    // Launch the URI.    bool success = await Windows.System.Launcher.LaunchUriAsync(uri, options);    if (success)    {       // URI launched: uri.AbsoluteUri    }    else    {        // URI launch failed.  uri.AbsoluteUri    }