AlertDialog behind the keyboard

Hi all, I have alert dialog in my applicaiton. I am creating as follows:

            AlertDialog.Builder builder = new AlertDialog.Builder(this)
            EditText input = new EditText(this);
            input.InputType = InputTypes.ClassNumber;
            builder.SetView(input);

            builder.SetMessage("Enter your Number");
            builder.SetCancelable(true);
            builder.Show()

I have two problems: - Keyboard is not showing automaticaly only after clicking on EditText - Keyboard is hide part of dialog button, how can i bid it higher ?