Making Async custom message box

Question

I have created a Custom Message Box class which when called displays a message box on the current page. I have also provided buttons inside of message box to accept user preference. After the custom message box is added to the page execution of methods continue.
I want to make the page wait until user opts an option from the message box just like existing MessageBox class.
I have created a method show() which displays the custom message box on the current page. How do I make it async to stop the execution till an option is selected by the user?

Answer 1

See
Quickstart: Calling asynchronous APIs in  C# or Visual Basic and
Asynchronous Programming with Async and Await for an overview of how the .Net async system works.
The tl;dr for your scenario is to have your ShowAsync() method return a Task so it can be awaited:
class CustomMessageDialog
public Task ShowAsync()
// Do whatever is needed to show the MessageDialog
public Task<int> ShowAndReturnAsync()
int indexChosen; // the index of the command picked by the user
// Do whatever is needed to show the MessageDialog
return indexChosen;