Use:

Private Sub DetailTextBox_PreviewTextInput( _
  ByVal sender As Object, _
  ByVal e As System.Windows.Input.TextCompositionEventArgs) _
  Handles DetailTextBox.PreviewTextInput

    If _IsANumber Then
        If Not Char.IsNumber(e.Text) Then
            e.Handled = True
        End If
    End If
End Sub

在使用这里的一些解决方案一段时间后，我开发了自己的解决方案，该解决方案适用于我的MVVM设置。注意，在允许用户输入错误字符的意义上，它不像其他一些那样动态，但它阻止用户按下按钮，从而阻止他们做任何事情。这很好地配合了我的主题，即当操作无法执行时将按钮变灰。

我有一个文本框，用户必须输入一些文档页面要打印:

<TextBox Text="{Binding NumberPagesToPrint, UpdateSourceTrigger=PropertyChanged}"/>

.．.使用这个绑定属性:

private string _numberPagesToPrint;
public string NumberPagesToPrint
{
    get { return _numberPagesToPrint; }
    set
    {
        if (_numberPagesToPrint == value)
        {
            return;
        }

        _numberPagesToPrint = value;
        OnPropertyChanged("NumberPagesToPrint");
    }
}

我还有一个按钮:

<Button Template="{DynamicResource CustomButton_Flat}" Content="Set"
        Command="{Binding SetNumberPagesCommand}"/>

.．.使用此命令绑定:

private RelayCommand _setNumberPagesCommand;
public ICommand SetNumberPagesCommand
{
    get
    {
        if (_setNumberPagesCommand == null)
        {
            int num;
            _setNumberPagesCommand = new RelayCommand(param => SetNumberOfPages(),
                () => Int32.TryParse(NumberPagesToPrint, out num));
        }

        return _setNumberPagesCommand;
    }
}

然后是SetNumberOfPages()方法，但对于本主题不重要。它在我的案例中工作得很好，因为我不需要向视图的代码隐藏文件中添加任何代码，并且它允许我使用Command属性控制行为。

我使用了一些已经在这里的东西，并使用一个行为把我自己的扭曲，这样我就不必在大量的视图中传播这段代码……

public class AllowableCharactersTextBoxBehavior : Behavior<TextBox>
{
    public static readonly DependencyProperty RegularExpressionProperty =
         DependencyProperty.Register("RegularExpression", typeof(string), typeof(AllowableCharactersTextBoxBehavior),
         new FrameworkPropertyMetadata(".*"));
    public string RegularExpression
    {
        get
        {
            return (string)base.GetValue(RegularExpressionProperty);
        }
        set
        {
            base.SetValue(RegularExpressionProperty, value);
        }
    }

    public static readonly DependencyProperty MaxLengthProperty =
        DependencyProperty.Register("MaxLength", typeof(int), typeof(AllowableCharactersTextBoxBehavior),
        new FrameworkPropertyMetadata(int.MinValue));
    public int MaxLength
    {
        get
        {
            return (int)base.GetValue(MaxLengthProperty);
        }
        set
        {
            base.SetValue(MaxLengthProperty, value);
        }
    }

    protected override void OnAttached()
    {
        base.OnAttached();
        AssociatedObject.PreviewTextInput += OnPreviewTextInput;
        DataObject.AddPastingHandler(AssociatedObject, OnPaste);
    }

    private void OnPaste(object sender, DataObjectPastingEventArgs e)
    {
        if (e.DataObject.GetDataPresent(DataFormats.Text))
        {
            string text = Convert.ToString(e.DataObject.GetData(DataFormats.Text));

            if (!IsValid(text, true))
            {
                e.CancelCommand();
            }
        }
        else
        {
            e.CancelCommand();
        }
    }

    void OnPreviewTextInput(object sender, System.Windows.Input.TextCompositionEventArgs e)
    {
        e.Handled = !IsValid(e.Text, false);
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        AssociatedObject.PreviewTextInput -= OnPreviewTextInput;
        DataObject.RemovePastingHandler(AssociatedObject, OnPaste);
    }

    private bool IsValid(string newText, bool paste)
    {
        return !ExceedsMaxLength(newText, paste) && Regex.IsMatch(newText, RegularExpression);
    }

    private bool ExceedsMaxLength(string newText, bool paste)
    {
        if (MaxLength == 0) return false;

        return LengthOfModifiedText(newText, paste) > MaxLength;
    }

    private int LengthOfModifiedText(string newText, bool paste)
    {
        var countOfSelectedChars = this.AssociatedObject.SelectedText.Length;
        var caretIndex = this.AssociatedObject.CaretIndex;
        string text = this.AssociatedObject.Text;

        if (countOfSelectedChars > 0 || paste)
        {
            text = text.Remove(caretIndex, countOfSelectedChars);
            return text.Length + newText.Length;
        }
        else
        {
            var insert = Keyboard.IsKeyToggled(Key.Insert);

            return insert && caretIndex < text.Length ? text.Length : text.Length + newText.Length;
        }
    }
}

下面是相关的视图代码:

<TextBox MaxLength="50" TextWrapping="Wrap" MaxWidth="150" Margin="4"
 Text="{Binding Path=FileNameToPublish}" >
     <interactivity:Interaction.Behaviors>
         <v:AllowableCharactersTextBoxBehavior RegularExpression="^[0-9.\-]+$" MaxLength="50" />
     </interactivity:Interaction.Behaviors>
</TextBox>

我们可以对文本框更改事件进行验证。下面的实现可以防止除数字和一个小数点以外的按键输入。

private void textBoxNumeric_TextChanged(object sender, TextChangedEventArgs e) 
{         
      TextBox textBox = sender as TextBox;         
      Int32 selectionStart = textBox.SelectionStart;         
      Int32 selectionLength = textBox.SelectionLength;         
      String newText = String.Empty;         
      int count = 0;         
      foreach (Char c in textBox.Text.ToCharArray())         
      {             
         if (Char.IsDigit(c) || Char.IsControl(c) || (c == '.' && count == 0))             
         {                 
            newText += c;                 
            if (c == '.')                     
              count += 1;             
         }         
     }         
     textBox.Text = newText;         
     textBox.SelectionStart = selectionStart <= textBox.Text.Length ? selectionStart :        textBox.Text.Length;     
} 

事件处理程序正在预览文本输入。在这里，正则表达式只在文本输入不是数字时才匹配文本输入，然后它就不会进入文本框。

如果只需要字母，则将正则表达式替换为[^a-zA-Z]。

XAML

<TextBox Name="NumberTextBox" PreviewTextInput="NumberValidationTextBox"/>

XAML.CS文件

using System.Text.RegularExpressions;
private void NumberValidationTextBox(object sender, TextCompositionEventArgs e)
{
    Regex regex = new Regex("[^0-9]+");
    e.Handled = regex.IsMatch(e.Text);
}

Use:

Private Sub DetailTextBox_PreviewTextInput( _
  ByVal sender As Object, _
  ByVal e As System.Windows.Input.TextCompositionEventArgs) _
  Handles DetailTextBox.PreviewTextInput

    If _IsANumber Then
        If Not Char.IsNumber(e.Text) Then
            e.Handled = True
        End If
    End If
End Sub