Update Microsoft.Toolkit.Uwp.UI/Extensions/TextBox/TextBoxExtensions.Mask.Internals.cs

This makes sense. We shouldn't ignore the casing.

Co-authored-by: Nirmal Guru <Nirmal4G@gmail.com>

Author: puppetsw

Microsoft.Toolkit.Uwp.UI/Extensions/TextBox/TextBoxExtensions.Mask.Internals.cs

@@ -298,7 +298,7 @@ private static void Textbox_TextChanging(TextBox textbox, TextBoxTextChangingEve
             if (oldSelectionStart >= oldText.Length && !isDeleteOrBackspace)
             {
                 // ignore change(s) if oldtext is a substring of new text value
-                if (textbox.Text.Contains(oldText, StringComparison.OrdinalIgnoreCase))
+                if (textbox.Text.Contains(oldText))
                 {
                     textbox.Text = oldText;
 
@@ -435,4 +435,4 @@ private static int GetSelectionStart(string mask, List<int> escapedChars, int se
             return selectionIndex;
         }
     }
-}
+}