use a boolean property instead of a char property for backward-compatibility

Microsoft.Toolkit.Uwp.UI/Extensions/TextBoxMask/TextBoxMask.Properties.cs

@@ -30,10 +30,10 @@ namespace Microsoft.Toolkit.Uwp.UI.Extensions
         public static readonly DependencyProperty CustomMaskProperty = DependencyProperty.RegisterAttached("CustomMask", typeof(string), typeof(TextBoxMask), new PropertyMetadata(null, InitTextBoxMask));
 
         /// <summary>
-        /// Represents the character that's used to escape variables in the mask
+        /// Represents whether the variables in the mask can be escaped
         /// </summary>
-        public static readonly DependencyProperty EscapeCharacterProperty =
-            DependencyProperty.RegisterAttached("EscapeCharacter", typeof(string), typeof(TextBoxMask), new PropertyMetadata("\0"));
+        public static readonly DependencyProperty EscapeVariablesProperty =
+            DependencyProperty.RegisterAttached("EscapeVariables", typeof(bool), typeof(TextBoxMask), new PropertyMetadata(false, InitTextBoxMask));
 
         private static readonly DependencyProperty RepresentationDictionaryProperty = DependencyProperty.RegisterAttached("RepresentationDictionary", typeof(Dictionary<char, string>), typeof(TextBoxMask), new PropertyMetadata(null));
         private static readonly DependencyProperty OldTextProperty = DependencyProperty.RegisterAttached("OldText", typeof(string), typeof(TextBoxMask), new PropertyMetadata(null));
@@ -42,7 +42,7 @@ namespace Microsoft.Toolkit.Uwp.UI.Extensions
         private static readonly DependencyProperty OldSelectionStartProperty = DependencyProperty.RegisterAttached("OldSelectionStart", typeof(int), typeof(TextBoxMask), new PropertyMetadata(0));
 
         private static readonly DependencyProperty EscapedMaskProperty = DependencyProperty.RegisterAttached("EscapedMask", typeof(string), typeof(TextBoxMask), new PropertyMetadata(null));
-        private static readonly DependencyProperty MaskEscapedCharIndecesProperty = DependencyProperty.RegisterAttached("MaskEscapedCharIndeces", typeof(List<int>), typeof(TextBoxMask), new PropertyMetadata(null));
+        private static readonly DependencyProperty MaskEscapedCharactersProperty = DependencyProperty.RegisterAttached("MaskEscapedCharacters", typeof(List<int>), typeof(TextBoxMask), new PropertyMetadata(null));
 
         /// <summary>
         /// Gets mask value
@@ -109,19 +109,19 @@ namespace Microsoft.Toolkit.Uwp.UI.Extensions
         /// </summary>
         /// <param name="obj"></param>
         /// <returns></returns>
-        public static string GetEscapeCharacter(DependencyObject obj)
+        public static bool GetEscapeVariables(DependencyObject obj)
         {
-            return (string)obj.GetValue(EscapeCharacterProperty);
+            return (bool)obj.GetValue(EscapeVariablesProperty);
         }
 
         /// <summary>
-        /// Sets EscapeCharacter property which represents the character that's used to escape variables in the mask
+        /// Sets EscapeCharacter property which determines whether the variables in the mask can be escaped
         /// </summary>
         /// <param name="obj"></param>
         /// <param name="value"></param>
-        public static void SetEscapeCharacter(DependencyObject obj, string value)
+        public static void SetEscapeVariables(DependencyObject obj, bool value)
         {
-            obj.SetValue(EscapeCharacterProperty, value);
+            obj.SetValue(EscapeVariablesProperty, value);
         }
     }
 }

Microsoft.Toolkit.Uwp.UI/Extensions/TextBoxMask/TextBoxMask.cs

@@ -18,6 +18,7 @@ namespace Microsoft.Toolkit.Uwp.UI.Extensions
     public partial class TextBoxMask
     {
         private const string DefaultPlaceHolder = "_";
+        private const char EscapeChar = '\\';
         private static readonly KeyValuePair<char, string> AlphaCharacterRepresentation = new KeyValuePair<char, string>('a', "[A-Za-z]");
         private static readonly KeyValuePair<char, string> NumericCharacterRepresentation = new KeyValuePair<char, string>('9', "[0-9]");
         private static readonly KeyValuePair<char, string> AlphaNumericRepresentation = new KeyValuePair<char, string>('*', "[A-Za-z0-9]");
@@ -56,28 +57,30 @@ namespace Microsoft.Toolkit.Uwp.UI.Extensions
                 throw new ArgumentException("PlaceHolder can't be null or empty");
             }
 
-            var escapeCharValue = textbox.GetValue(EscapeCharacterProperty) as string;
-            if (string.IsNullOrEmpty(escapeCharValue))
-            {
-                throw new ArgumentException("EscapeCharacter can't be null or empty.");
-            }
-
-            var escape = escapeCharValue[0];
-
             var escapedChars = new List<int>();
-            var builder = new StringBuilder(mask);
-            for (int i = 0; i < builder.Length - 1; i++)
+
+            string escapedMask;
+            var shouldEscapeVariables = (bool)textbox.GetValue(EscapeVariablesProperty);
+            if (shouldEscapeVariables)
             {
-                if (builder[i] == escape)
+                var builder = new StringBuilder(mask);
+                for (int i = 0; i < builder.Length - 1; i++)
                 {
-                    escapedChars.Add(i);
-                    builder.Remove(i, 1);
+                    if (builder[i] == EscapeChar)
+                    {
+                        escapedChars.Add(i);
+                        builder.Remove(i, 1);
+                    }
                 }
+                escapedMask = builder.ToString();
+            }
+            else
+            {
+                escapedMask = mask;
             }
 
-            var escapedMask = builder.ToString();
-            textbox.SetValue(MaskEscapedCharIndecesProperty, escapedChars);
-            textbox.SetValue(EscapeCharacterProperty, escapedMask);
+            textbox.SetValue(MaskEscapedCharactersProperty, escapedChars);
+            textbox.SetValue(EscapedMaskProperty, escapedMask);
 
             var placeHolder = placeHolderValue[0];
 
@@ -208,7 +211,7 @@ namespace Microsoft.Toolkit.Uwp.UI.Extensions
             }
 
             var escapedMask = textbox.GetValue(EscapedMaskProperty) as string;
-            var escapedChars = textbox.GetValue(MaskEscapedCharIndecesProperty) as List<int>;
+            var escapedChars = textbox.GetValue(MaskEscapedCharactersProperty) as List<int>;
 
             // to update the textbox text without triggering TextChanging text
             int oldSelectionStart = (int)textbox.GetValue(OldSelectionStartProperty);
@@ -264,8 +267,8 @@ namespace Microsoft.Toolkit.Uwp.UI.Extensions
         private static void Textbox_TextChanging(TextBox textbox, TextBoxTextChangingEventArgs args)
         {
             var mask = textbox.GetValue(MaskProperty) as string;
-            var escapedMask = textbox.GetValue(EscapeCharacterProperty) as string;
-            var escapedChars = textbox.GetValue(MaskEscapedCharIndecesProperty) as List<int>;
+            var escapedMask = textbox.GetValue(EscapedMaskProperty) as string;
+            var escapedChars = textbox.GetValue(MaskEscapedCharactersProperty) as List<int>;
 
             var representationDictionary = textbox.GetValue(RepresentationDictionaryProperty) as Dictionary<char, string>;
             var placeHolderValue = textbox?.GetValue(PlaceHolderProperty) as string;