Created
January 13, 2017 21:16
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WPF TextBox Input Restrictions
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/// <summary> | |
/// Provides masking behavior for any TextBox | |
/// </summary> | |
public static class Masking | |
{ | |
private static readonly DependencyPropertyKey _maskExpressionPropertyKey = DependencyProperty.RegisterAttachedReadOnly(""MaskExpression"", | |
typeof(Regex), | |
typeof(Masking), | |
new FrameworkPropertyMetadata()); | |
/// <summary> | |
/// Identifies the <see cref=""Mask""/> dependency property. | |
/// </summary> | |
public static readonly DependencyProperty MaskProperty = DependencyProperty.RegisterAttached(""Mask"", | |
typeof(string), | |
typeof(Masking), | |
new FrameworkPropertyMetadata(OnMaskChanged)); | |
/// <summary> | |
/// Identifies the <see cref=""MaskExpression""/> dependency property. | |
/// </summary> | |
public static readonly DependencyProperty MaskExpressionProperty = _maskExpressionPropertyKey.DependencyProperty; | |
/// <summary> | |
/// Gets the mask for a given <see cref=""TextBox""/>. | |
/// </summary> | |
/// <param name=""textBox""> | |
/// The <see cref=""TextBox""/> whose mask is to be retrieved. | |
/// </param> | |
/// <returns> | |
/// The mask, or <see langword=""null""/> if no mask has been set. | |
/// </returns> | |
public static string GetMask(TextBox textBox) | |
{ | |
if (textBox == null) | |
{ | |
throw new ArgumentNullException(""textBox""); | |
} | |
return textBox.GetValue(MaskProperty) as string; | |
} | |
/// <summary> | |
/// Sets the mask for a given <see cref=""TextBox""/>. | |
/// </summary> | |
/// <param name=""textBox""> | |
/// The <see cref=""TextBox""/> whose mask is to be set. | |
/// </param> | |
/// <param name=""mask""> | |
/// The mask to set, or <see langword=""null""/> to remove any existing mask from <paramref name=""textBox""/>. | |
/// </param> | |
public static void SetMask(TextBox textBox, string mask) | |
{ | |
if (textBox == null) | |
{ | |
throw new ArgumentNullException(""textBox""); | |
} | |
textBox.SetValue(MaskProperty, mask); | |
} | |
/// <summary> | |
/// Gets the mask expression for the <see cref=""TextBox""/>. | |
/// </summary> | |
/// <remarks> | |
/// This method can be used to retrieve the actual <see cref=""Regex""/> instance created as a result of setting the mask on a <see cref=""TextBox""/>. | |
/// </remarks> | |
/// <param name=""textBox""> | |
/// The <see cref=""TextBox""/> whose mask expression is to be retrieved. | |
/// </param> | |
/// <returns> | |
/// The mask expression as an instance of <see cref=""Regex""/>, or <see langword=""null""/> if no mask has been applied to <paramref name=""textBox""/>. | |
/// </returns> | |
public static Regex GetMaskExpression(TextBox textBox) | |
{ | |
if (textBox == null) | |
{ | |
throw new ArgumentNullException(""textBox""); | |
} | |
return textBox.GetValue(MaskExpressionProperty) as Regex; | |
} | |
private static void SetMaskExpression(TextBox textBox, Regex regex) | |
{ | |
textBox.SetValue(_maskExpressionPropertyKey, regex); | |
} | |
private static void OnMaskChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e) | |
{ | |
var textBox = dependencyObject as TextBox; | |
var mask = e.NewValue as string; | |
textBox.PreviewTextInput -= textBox_PreviewTextInput; | |
textBox.PreviewKeyDown -= textBox_PreviewKeyDown; | |
DataObject.RemovePastingHandler(textBox, Pasting); | |
if (mask == null) | |
{ | |
textBox.ClearValue(MaskProperty); | |
textBox.ClearValue(MaskExpressionProperty); | |
} | |
else | |
{ | |
textBox.SetValue(MaskProperty, mask); | |
SetMaskExpression(textBox, new Regex(mask, RegexOptions.Compiled | RegexOptions.IgnorePatternWhitespace)); | |
textBox.PreviewTextInput += textBox_PreviewTextInput; | |
textBox.PreviewKeyDown += textBox_PreviewKeyDown; | |
DataObject.AddPastingHandler(textBox, Pasting); | |
} | |
} | |
private static void textBox_PreviewTextInput(object sender, TextCompositionEventArgs e) | |
{ | |
var textBox = sender as TextBox; | |
var maskExpression = GetMaskExpression(textBox); | |
if (maskExpression == null) | |
{ | |
return; | |
} | |
var proposedText = GetProposedText(textBox, e.Text); | |
if (!maskExpression.IsMatch(proposedText)) | |
{ | |
e.Handled = true; | |
} | |
} | |
private static void textBox_PreviewKeyDown(object sender, KeyEventArgs e) | |
{ | |
var textBox = sender as TextBox; | |
var maskExpression = GetMaskExpression(textBox); | |
if (maskExpression == null) | |
{ | |
return; | |
} | |
//pressing space doesn't raise PreviewTextInput - no idea why, but we need to handle | |
//explicitly here | |
if (e.Key == Key.Space) | |
{ | |
var proposedText = GetProposedText(textBox, "" ""); | |
if (!maskExpression.IsMatch(proposedText)) | |
{ | |
e.Handled = true; | |
} | |
} | |
} | |
private static void Pasting(object sender, DataObjectPastingEventArgs e) | |
{ | |
var textBox = sender as TextBox; | |
var maskExpression = GetMaskExpression(textBox); | |
if (maskExpression == null) | |
{ | |
return; | |
} | |
if (e.DataObject.GetDataPresent(typeof(string))) | |
{ | |
var pastedText = e.DataObject.GetData(typeof(string)) as string; | |
var proposedText = GetProposedText(textBox, pastedText); | |
if (!maskExpression.IsMatch(proposedText)) | |
{ | |
e.CancelCommand(); | |
} | |
} | |
else | |
{ | |
e.CancelCommand(); | |
} | |
} | |
private static string GetProposedText(TextBox textBox, string newText) | |
{ | |
var text = textBox.Text; | |
if (textBox.SelectionStart != -1) | |
{ | |
text = text.Remove(textBox.SelectionStart, textBox.SelectionLength); | |
} | |
text = text.Insert(textBox.CaretIndex, newText); | |
return text; | |
} | |
} |
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NOTE:
Attached behavior must be used like this:
<TextBox b:Masking.Mask=""^\p{Lu}*$""></TextBox>
Taken from StackOverflow:
http://stackoverflow.com/questions/1103765/how-to-define-textbox-input-restrictions"