我对此有一个稍微简化的答案(只有PreviewMouseLeftButtonDown事件)，这似乎模仿了浏览器的常用功能:

在XAML中，你有一个文本框说:

<TextBox Text="http://www.blabla.com" BorderThickness="2" BorderBrush="Green" VerticalAlignment="Center" Height="25"
                 PreviewMouseLeftButtonDown="SelectAll" />

在后台代码:

private void SelectAll(object sender, MouseButtonEventArgs e)
{
    TextBox tb = (sender as TextBox);

    if (tb == null)
    {
        return;
    }

    if (!tb.IsKeyboardFocusWithin)
    {
        tb.SelectAll();
        e.Handled = true;
        tb.Focus();
    }
}

我以为这样简单多了。

nameOfTextbox.Focus();
nameOfTextbox.Select(0, nameOfTextbox.Text.Length);

同样，如果别人有你的光标不聚焦在文本框的问题，你可以使用这个在nameOfTextbox.Focus();以上。

Dispatcher.BeginInvoke(DispatcherPriority.Input,
new Action(delegate () {
    nameOfTextbox.Focus();         // Set Logical Focus
    Keyboard.Focus(nameOfTextbox); // Set Keyboard Focus
}));

不知道为什么它在GotFocus事件中失去了选择。

但是一个解决方案是在GotKeyboardFocus和GotMouseCapture事件上进行选择。这样它就能一直工作。

——编辑——

在这里添加一个例子来告诉人们如何解决上面提到的一些缺点:

private void TextBox_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
    // Fixes issue when clicking cut/copy/paste in context menu
    if (textBox.SelectionLength == 0) 
        textBox.SelectAll();
}

private void TextBox_LostMouseCapture(object sender, MouseEventArgs e)
{
    // If user highlights some text, don't override it
    if (textBox.SelectionLength == 0) 
        textBox.SelectAll();

    // further clicks will not select all
    textBox.LostMouseCapture -= TextBox_LostMouseCapture; 
}

private void TextBox_LostKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
    // once we've left the TextBox, return the select all behavior
    textBox.LostMouseCapture += TextBox_LostMouseCapture;
}

我选择了部分Donnelle的答案(跳过双击)，因为我认为这更自然。然而，像grokies一样，我不喜欢创建派生类的需要。但我也不喜欢Grokys的OnStartup方法。我需要在“一般但不总是”的基础上这样做。

我已经实现了这作为一个附加的DependencyProperty，所以我可以设置local:SelectTextOnFocus。在xaml中Active =“True”。我觉得这种方式最令人愉快。

using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;

public class SelectTextOnFocus : DependencyObject
{
    public static readonly DependencyProperty ActiveProperty = DependencyProperty.RegisterAttached(
        "Active",
        typeof(bool),
        typeof(SelectTextOnFocus),
        new PropertyMetadata(false, ActivePropertyChanged));

    private static void ActivePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is TextBox)
        {
            TextBox textBox = d as TextBox;
            if ((e.NewValue as bool?).GetValueOrDefault(false))
            {
                textBox.GotKeyboardFocus += OnKeyboardFocusSelectText;
                textBox.PreviewMouseLeftButtonDown += OnMouseLeftButtonDown;
            }
            else
            {
                textBox.GotKeyboardFocus -= OnKeyboardFocusSelectText;
                textBox.PreviewMouseLeftButtonDown -= OnMouseLeftButtonDown;
            }
        }
    }

    private static void OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        DependencyObject dependencyObject = GetParentFromVisualTree(e.OriginalSource);

        if (dependencyObject == null)
        {
            return;
        }

        var textBox = (TextBox)dependencyObject;
        if (!textBox.IsKeyboardFocusWithin)
        {
            textBox.Focus();
            e.Handled = true;
        }
    }

    private static DependencyObject GetParentFromVisualTree(object source)
    {
        DependencyObject parent = source as UIElement;
        while (parent != null && !(parent is TextBox))
        {
            parent = VisualTreeHelper.GetParent(parent);
        }

        return parent;
    }

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

    [AttachedPropertyBrowsableForChildrenAttribute(IncludeDescendants = false)]
    [AttachedPropertyBrowsableForType(typeof(TextBox))]
    public static bool GetActive(DependencyObject @object)
    {
        return (bool) @object.GetValue(ActiveProperty);
    }

    public static void SetActive(DependencyObject @object, bool value)
    {
        @object.SetValue(ActiveProperty, value);
    }
}

对于我的“一般但不总是”功能，我在(全局)文本框样式中将这个附件属性设置为True。这样，“选择文本”总是“打开”的，但我可以在每个文本框的基础上禁用它。

以下是@Nasenbaer发布的答案的c#版本

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);
}

而MyTextBox_GotFocus是分配给MyTextBox的GotFocus事件的事件处理程序。

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);
}