/// <summary>
/// Starts the user interface that prompts a user for a certificate.
/// </summary>
/// <param name="channel">The client channel.</param>
/// <param name="callback">The callback object.</param>
/// <param name="state">Any state data.</param>
/// <returns>The System.IAsyncResult to use to call back when processing has completed.</returns>
public IAsyncResult BeginDisplayInitializationUI(IClientChannel channel, AsyncCallback callback, Object state)
{
// Any worker thread can request a channel, so the user prompt needs to be invoked on a Single Threaded Apartment (STA) thread. This will create that
// thread and communicate to it the current state of the channel.
CredentialAsyncResult credentialAsyncResult = new CredentialAsyncResult()
{
AsyncCallback = callback,
AsyncState = state,
Credentials = this.Credentials,
IClientChannel = channel
};
// Only single threaded apartments are allowed to call the user interface to prompt the user. Background threads must wait until an apartment that can
// prompt the user has validated the credentials.
if (Thread.CurrentThread.GetApartmentState() == ApartmentState.STA)
{
// Only prompt the user once for their credentials. After a set of credentials are chosen, they'll be used by all subsequent calls to use this
// channel until the 'IsPrompted' flag is cleared.
if (InteractiveChannelInitializer.IsPrompted)
{
// This will prompt the user for their credentials. It effectively creates a modal dialog box and prevents the other threads from executing,
// which effectively obviates the whole IAsyncResult strategy here, but this was the only way to come up with a consistent way to call the
// channels from the console or a Windows environment. Note that the frame will only return control to this thread when we set the 'Continue'
// property to 'false'.
DispatcherFrame dispatcherFrame = new DispatcherFrame();
dispatcherFrame.Dispatcher.BeginInvoke(DispatcherPriority.Normal, this.Prompt, credentialAsyncResult);
dispatcherFrame.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action(() => dispatcherFrame.Continue = false));
Dispatcher.PushFrame(dispatcherFrame);
}
else
{
// If we have already prompted the user then return the credentials immediately.
credentialAsyncResult.Credentials = this.Credentials;
credentialAsyncResult.SetCompletedSynchronously();
}
}
else
{
// The non-UI threads must wait here until a UI thread has validated the credentials.
InteractiveChannelInitializer.ValidCredentials.WaitOne();
// Setting the credentials in this way will make the channel act synchronously (that is, without prompting the user). This is important after the
// first time the channel has been initialized as we don't want to keep bother the user for credentials.
credentialAsyncResult.Credentials = this.Credentials;
credentialAsyncResult.SetCompletedSynchronously();
}
// This will be used by the caller to manage the asynchronous task that prompts the user and then invoke the EndDisplayInitializationUI with the results
// of the dialog.
return(credentialAsyncResult);
}
