static async void SendTweetWithSinglePicture(string message, string image)
{
var auth = new SingleUserAuthorizer
{
CredentialStore = new SingleUserIn
You should use PageAsyncTask. It has samples in MSDN page.
// Register the asynchronous task.
Page.RegisterAsyncTask(new PageAsyncTask(SendTweetWithSinglePicture(message, image));
// Execute the register asynchronous task.
Page.ExecuteRegisteredAsyncTasks();
as I pointed the sample and explanations on MSDN page is pretty good.