#region TextBoxIDCard selection
private bool textBoxIDCardGotFocus = false;
private void TextBoxIDCard_GotFocus(object sender, RoutedEventArgs e)
{
    this.TextBoxIDCard.SelectAll();
}

private void TextBoxIDCard_LostFocus(object sender, RoutedEventArgs e)
{
    textBoxIDCardGotFocus = false;
}

private void TextBoxIDCard_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
    if (textBoxIDCardGotFocus == false)
    {
        e.Handled = true;
        this.TextBoxIDCard.Focus();
        textBoxIDCardGotFocus = true;
    }
} 
#endregion

我也有同样的问题。在VB。Net的工作方式很简单:

VB XAML:

<TextBox x:Name="txtFilterFrequency" />

Codehind:

Private Sub txtFilterText_GotFocus(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles txtFilterText.GotFocus
    Me.Dispatcher.BeginInvoke(Sub()
                                  txtFilterText.SelectAll()
                              End Sub, DispatcherPriority.ApplicationIdle, Nothing)
End Sub

c#(感谢ViRuSTriNiTy)

private delegate void TextBoxSelectAllDelegate(object sender);

private void TextBoxSelectAll(object sender)
{
    (sender as System.Windows.Controls.TextBox).SelectAll();
}

private void MyTextBox_GotFocus(object sender, System.Windows.RoutedEventArgs e)
{
    TextBoxSelectAllDelegate d = TextBoxSelectAll;

    this.Dispatcher.BeginInvoke(d,
        System.Windows.Threading.DispatcherPriority.ApplicationIdle, sender);
}

尝试这个扩展方法，添加所需的行为到任何文本框控件。我还没有对它进行广泛测试，但它似乎满足了我的需求。

public static class TextBoxExtensions
{
    public static void SetupSelectAllOnGotFocus(this TextBox source)
    {
        source.GotFocus += SelectAll;
        source.PreviewMouseLeftButtonDown += SelectivelyIgnoreMouseButton;
    }

    private static void SelectAll(object sender, RoutedEventArgs e)
    {
        var textBox = e.OriginalSource as TextBox;
        if (textBox != null)
            textBox.SelectAll();
    }

    private static void SelectivelyIgnoreMouseButton(object sender, MouseButtonEventArgs e)
    {
        var textBox = (sender as TextBox);
        if (textBox != null)
        {
            if (!textBox.IsKeyboardFocusWithin)
            {
                e.Handled = true;
                textBox.Focus();
            }
        }
    }
}

在App.xaml文件中:

<Application.Resources>
    <Style TargetType="TextBox">
        <EventSetter Event="GotKeyboardFocus" Handler="TextBox_GotKeyboardFocus"/>
    </Style>
</Application.Resources>

在App.xaml.cs文件中:

private void TextBox_GotKeyboardFocus(Object sender, KeyboardFocusChangedEventArgs e)
{
    ((TextBox)sender).SelectAll();
}

有了这段代码，你可以在你的应用程序中找到所有的文本框。

这似乎对我有用……

private bool TextBoxFocusBool;

private void TextBox_GotFocus(object sender, RoutedEventArgs e)
{
    TextBoxFocusBool = true;
}

private void TextBox_LostMouseCapture(object sender, MouseEventArgs e)
{
    if (TextBox.SelectionLength == 0 & TextBoxFocusBool == true)
    {
        TextBox.SelectAll();
        TextBoxFocusBool = false;
    }
}

private void TextBox_LostFocus(object sender, RoutedEventArgs e)
{
    TextBoxFocusBool = true;
}

我用附加行为解决了这个问题，而不是谢尔盖回答中的表达式行为。这意味着我不需要依赖Blend SDK中的System.Windows.Interactivity:

public class TextBoxBehavior
{
    public static bool GetSelectAllTextOnFocus(TextBox textBox)
    {
        return (bool)textBox.GetValue(SelectAllTextOnFocusProperty);
    }

    public static void SetSelectAllTextOnFocus(TextBox textBox, bool value)
    {
        textBox.SetValue(SelectAllTextOnFocusProperty, value);
    }

    public static readonly DependencyProperty SelectAllTextOnFocusProperty =
        DependencyProperty.RegisterAttached(
            "SelectAllTextOnFocus",
            typeof (bool),
            typeof (TextBoxBehavior),
            new UIPropertyMetadata(false, OnSelectAllTextOnFocusChanged));

    private static void OnSelectAllTextOnFocusChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var textBox = d as TextBox;
        if (textBox == null) return;

        if (e.NewValue is bool == false) return;

        if ((bool) e.NewValue)
        {
            textBox.GotFocus += SelectAll;
            textBox.PreviewMouseDown += IgnoreMouseButton;
        }
        else
        {
            textBox.GotFocus -= SelectAll;
            textBox.PreviewMouseDown -= IgnoreMouseButton;
        }
    }

    private static void SelectAll(object sender, RoutedEventArgs e)
    {
        var textBox = e.OriginalSource as TextBox;
        if (textBox == null) return;
        textBox.SelectAll();
    }

    private static void IgnoreMouseButton(object sender, System.Windows.Input.MouseButtonEventArgs e)
    {
        var textBox = sender as TextBox;
        if (textBox == null || (!textBox.IsReadOnly && textBox.IsKeyboardFocusWithin)) return;

        e.Handled = true;
        textBox.Focus();
    }
}

然后你可以像这样在XAML中使用它:

<TextBox Text="Some Text" behaviors:TextBoxBehavior.SelectAllTextOnFocus="True"/>

我在这里写过博客。