The control has problems when selecting, overtyping and inserting content.

Type something:

Select all text:

Type "1":

I'd expect the entire existing content to be deleted and new value to be "1".

Same goes for inserting a character:

Attempt to insert "4" between "3" and "5":

"5" is overtyped. Inserting doesn't work.

sample MaskedInput definition:

_Telephone = new RadMaskedInput
            { 
                Mask = "[(][0-9]{3}[)] [0-9]{3}-[0-9]{4}",
                MaskType = MaskType.Regex,
                WatermarkText = "Phone # (999) 999-9999",
                RejectedSymbolErrorText = "Only Numbers Allowed!",
                InvalidInputErrorText = "Invalid Input",
                WatermarkTextColor = Color.Black,
                ErrorColor = Color.Red,
                DisplayedTextColor = Color.Black,
            };

            _Telephone.InputValue = "2223334444";
            Grid.Children.Add(_Telephone, 0, 0);

and the result:

An exception is thrown in iOS when attempting to paste something that will result in the text being longer than the mask.

Available in the R3 2018 SP release.

Implement a Keyboard property which will allow users to set the virtual keyboard according to the expected input

Available in R2 2018 SP release.

The Xamarin.Forms MaskedInput control running on Android with the SwiftKey keyboard app installed does not allow for correct text entry and causes the app to Crash. Using the default keyboard the control works correctly.