How to prevent Alert Dialog from being shut down

Question

I am using c# and Xamarin.Android.
I want to create an app, and when it realized it has a new version, it will let user download the new version and force itself off.
So I used AlertDialog.
My code:

            if (NeedUpdate)
        {
            alertDialog = null;
            builder = new AlertDialog.Builder(this);
            alertDialog = builder
            .SetTitle("New Version")
            .SetMessage("please update the app to the latest version.")
            .SetPositiveButton("OK", (s, e) =>
            {
            })
            .Create();       //Create alertDialog

            alertDialog.Show();
            var dialog = new AlertDialog.Builder(this);
        }

In my code, NeedUpdate is a variable to store whether there's a new version.
But the question has begun.
In this app, the AlertDialog is translucent.
So the user can click on the translucent area to close it (without triggering the event I wrote).
I just want to ask, how to avoid user to close it without triggering the event I wrote, or if that's a event for what I said?
I admit, it's a very bad idea that force my users to update the app.
But I just want to know how to achieve it. Who have solutions?

PS:Some parts of the article is translated by machine, include this sentence.

Answer 1

Well i guess you could do the following

alertDialog.SetCancelable(false); 

Also if the above is what you want have you checked the Google Play core's playstore update plugin?