如何定义TextBox输入限制？
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如何限制TextBox仅接受大写字母，例如数字，或禁止放置任何特殊字符？
当然，抓住TextInput事件并在此处理文本是一块蛋糕，但这是否是正确的方法呢？
答案
我以前用附加的行为完成了这个，可以像这样使用：
<TextBox b:Masking.Mask="^p{Lu}*$"/>
附加的行为代码如下所示：
/// <summary>
/// Provides masking behavior for any <see cref="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;
}
}
另一答案
我通过处理以前可能导致模式被违反的以下操作改进了Kent Boogaart的答案：
- 退格
- 以可能违反模式的方式选择和拖动文本
- 削减命令
例如，Kent Boogaart的答案允许用户首先输入“abc”进入“ac”，然后删除带有退格的“b”，这违反了以下正则表达式
^(a|ab|abc)$
用法（不变）：
<TextBox b:Masking.Mask="^p{Lu}*$"/>
面具类：
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 h以上是关于如何定义TextBox输入限制？的主要内容，如果未能解决你的问题，请参考以下文章