Launching a Protocol URI

Any app may request that the OS launch a protocol URI. This is achieved using the Windows.System.Launcher class.

The following excerpt from the MainPageViewModel constructs a URI by appending the protocol name with a custom message. The Launcher’s LaunchFileAsync method is then called like so:

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void LaunchProtocol()
{
    Launcher.LaunchUriAsync(new Uri("unleashed:" + protocolMessage));
}

The viewmodel contains a string property named ProtocolMessage, which allows the user to compose a message to be sent to a registered app for the protocol.

The view contains a TextBox that is bound to the ProtocolMessage property as shown:

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<TextBox Text="{Binding ProtocolMessage, Mode=TwoWay}"
                         Width="250"/>

The viewmodel contains an ICommand named launchProtocolCommand that calls the LaunchProtocol method:

launchProtocolCommand
           = new DelegateCommand(obj => LaunchProtocol());

A Button in the view is bound to the LaunchProtocolCommand property:

<Button Content="Launch Protocol" Command="{Binding LaunchProtocolCommand}" />

Tapping the button causes the protocol URI to be constructed, and the app is deactivated. The OS dispatches the URI to the app that is registered to handle the unleashed protocol. The OS launches the WPUnleashed.FileAndProtocolAssociations, and the app navigates to the ProtocolMessageView.xaml page, which is displayed in Figure 30.2.

FIGURE 30.2 The protocol message is displayed by the ProtocolMessageView.xaml page.

Protocol associations allow your app to communicate with other apps on the device and allow the user to select the app that best suits his or her needs for handling a particular protocol message.