Use memcpy instead of iterating in C#.
Add null checks. Also add CheckBox.IsChecked, a two-state version of Checked, so that bindings to a bool work on WinRT.
Test code: Use CheckBox.IsChecked instead of Checked to avoid conversion errors on WinRT. Also use feature detection while instantiating NumericUpDown in test code.
Add null check, and refactor method.
Fixes to Eto.Platform.Xaml.Graphics.