Silverlight 4 Asynchronous Issue

I am creating an application in Silverlight 4. The first screen the user comes in contact with is the Login screen (Login.xaml). I have written the following code in Login.xaml.cs file.

private void btnSubmit_Click(object sender, RoutedEventArgs e)
{
    //first validate if the user is authorised for this application
    if (this.ValidateEntry())
    {
        if (UserAuthenticationBL.AuthenticateUser(txtUserName.Text.Trim(), txtPassword.Password.Trim()))
        {
            //since the user is authenticated we will show the dashbo开发者_如何学编程ard screen
            this.Content = new MainPage();
        }
        else
        {
            this.ShowErrorMessage("Invalid username or password");
            txtUserName.Focus();
        }
    }
}

My problem is that the code gets executed before i get the data in the AuthenticateUser method. The code immediately comes down to the "Invalid username or password" and the list is loaded after all the execution on the xaml page has finished.

I know there is something going wrong with the Asynchronous thingi...and i also know i need to put an event to know when the loading has completed........

but i dont know how to go about it!!! can someone please put some light on this issue...

thank you.

---

If I understood it right, your AuthenticateUser method is running async, right?

You have to define a callback to the AuthenticateUserComplete event and run the method in the button submit event. In the callback write this if/else clause, then it will be called once the asynchronous method was completed.

Just one question, why are you doing asynchronously if your behavior should be synchronous? (You have to get the answer before deciding what to do).

This http://msdn.microsoft.com/en-us/library/aa719598%28VS.71%29.aspx may be helpful :)

Oscar