只需为您的文本框使用自定义模板；以下答案可能对您有所帮助：
Visible line count of a TextBlock
更新
更改答案以按 OP 预期工作。
<Style x:Key="Local_TextBox" TargetType="{x:Type TextBoxBase}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBoxBase}">
<Border Name="Border" Background="{TemplateBinding Background}">
<ScrollViewer x:Name="PART_ContentHost" />
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
设计师，
<DockPanel>
<TextBlock Text="{Binding ElementName=uiTextBox, Path=(local:AttachedProperties.BindableLineCount)}"/>
<TextBox x:Name="uiTextBox" TextWrapping="Wrap" local:AttachedProperties.HasBindableLineCount="True"
AcceptsReturn="True" Text="{Binding LongText}" Style="{StaticResource Local_TextBox}" />
</DockPanel>
附加属性，
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
namespace Cmsn.Software.Tutorials.numberedTextBox
{
public class AttachedProperties
{
#region BindableLineCount AttachedProperty
public static string GetBindableLineCount(DependencyObject obj)
{
return (string)obj.GetValue(BindableLineCountProperty);
}
public static void SetBindableLineCount(DependencyObject obj, string value)
{
obj.SetValue(BindableLineCountProperty, value);
}
// Using a DependencyProperty as the backing store for BindableLineCount. This enables animation, styling, binding, etc...
public static readonly DependencyProperty BindableLineCountProperty =
DependencyProperty.RegisterAttached(
"BindableLineCount",
typeof(string),
typeof(AttachedProperties),
new UIPropertyMetadata("1"));
#endregion // BindableLineCount AttachedProperty
#region HasBindableLineCount AttachedProperty
public static bool GetHasBindableLineCount(DependencyObject obj)
{
return (bool)obj.GetValue(HasBindableLineCountProperty);
}
public static void SetHasBindableLineCount(DependencyObject obj, bool value)
{
obj.SetValue(HasBindableLineCountProperty, value);
}
// Using a DependencyProperty as the backing store for HasBindableLineCount. This enables animation, styling, binding, etc...
public static readonly DependencyProperty HasBindableLineCountProperty =
DependencyProperty.RegisterAttached(
"HasBindableLineCount",
typeof(bool),
typeof(AttachedProperties),
new UIPropertyMetadata(
false,
new PropertyChangedCallback(OnHasBindableLineCountChanged)));
private static void OnHasBindableLineCountChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
var textBox = (TextBox)o;
if ((e.NewValue as bool?) == true)
{
textBox.SizeChanged += new SizeChangedEventHandler(box_SizeChanged);
textBox.SetValue(BindableLineCountProperty, textBox.LineCount.ToString());
}
else
{
textBox.SizeChanged -= new SizeChangedEventHandler(box_SizeChanged);
}
}
static void box_SizeChanged(object sender, SizeChangedEventArgs e)
{
var textBox = (TextBox)sender;
string x = string.Empty;
for (int i = 0; i < textBox.LineCount; i++)
{
x += i + 1 + "\n";
}
textBox.SetValue(BindableLineCountProperty, x);
}
#endregion // HasBindableLineCount AttachedProperty
}
}