<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:local="clr-namespace:CustomControlLib"><Style TargetType="{x:Type local:MyControl}"><Setter Property="Template"><Setter.Value><ControlTemplate TargetType="{x:Type local:MyControl}"><Border Background="{TemplateBinding Background}"BorderBrush="{TemplateBinding BorderBrush}"BorderThickness="{TemplateBinding BorderThickness}"><StackPanel><TextBlock x:Name="PART_TextBlock" /></StackPanel></Border></ControlTemplate></Setter.Value></Setter></Style>
</ResourceDictionary>

custom control的程序部分

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;namespace CustomControlLib
{public class MyControl : Button{private const string TextBlockPart = "PART_TextBlock";TextBlock textBlock;static MyControl(){DefaultStyleKeyProperty.OverrideMetadata(typeof(MyControl), new FrameworkPropertyMetadata(typeof(MyControl)));}public override void OnApplyTemplate() //OnApplyTemplate get called everytime a template is applied to the control,control update
        {base.OnApplyTemplate(); //Button有自己的OnApplyTemplate我们需要call这个beofre call我们自己写的OnApplyTemplate方法if (textBlock != null) //避免memory leak每次call OnApplyTemplate方法时都给同一个textBlock加上event
            {textBlock.TextInput -= new TextCompositionEventHandler(textBlock_TextInput);}textBlock = GetTemplateChild(TextBlockPart) as TextBlock;if (textBlock != null){textBlock.Text = "Set from code";textBlock.TextInput +=new TextCompositionEventHandler(textBlock_TextInput);}}private void textBlock_TextInput(object sender, TextCompositionEventArgs e){}}
}

使用该control<Window x:Class="CustomControlDemo.MainWindow"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:cc="clr-namespace:CustomControlLib;assembly=CustomControlLib"Title="MainWindow"Width="525"Height="350"><Grid><cc:MyControl /></Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;namespace CustomControlLib
{[TemplatePart(Name = TextBlockPart, Type = typeof(TextBlock))] //告诉使用template的作者这里x:Name为PART_TextBlock的control一定要是TextBlock类型的public class MyControl : Button{private const string TextBlockPart = "PART_TextBlock";TextBlock _textBlock; //避免每一次call OnApplyTemplate都在方法体里创建一个TextBlock，在方法前定义一个变量来储存protected TextBlock TextBlock{get {return _textBlock; }set{if (_textBlock != null) //避免memory leak每次call OnApplyTemplate方法时都给同一个textBlock加上event
                {_textBlock.TextInput -= new TextCompositionEventHandler(textBlock_TextInput);}_textBlock = value;if (_textBlock != null){_textBlock.Text = "Set from code";_textBlock.TextInput += new TextCompositionEventHandler(textBlock_TextInput);}}}static MyControl(){DefaultStyleKeyProperty.OverrideMetadata(typeof(MyControl), new FrameworkPropertyMetadata(typeof(MyControl)));}public override void OnApplyTemplate() //OnApplyTemplate get called everytime a template is applied to the control,control update
        {base.OnApplyTemplate(); //Button有自己的OnApplyTemplate我们需要call这个beofre call我们自己写的OnApplyTemplate方法
            TextBlock = GetTemplateChild(TextBlockPart) as TextBlock; //每次call都赋值属性
        }private void textBlock_TextInput(object sender, TextCompositionEventArgs e){}}
}

TemplatePart(Name="PART_Decrease", Type=typeof(RepeatButton))

一直没明白这是干嘛用的，搜了一下，记载一下。

以Button的定义为例：

namespace System.Windows.Controls
{// Summary://     Represents a button control, which reacts to the Click event.[TemplatePart(Name = "Normal State", Type = typeof(Storyboard))][TemplatePart(Name = "MouseOver State", Type = typeof(Storyboard))][TemplatePart(Name = "RootElement", Type = typeof(FrameworkElement))][TemplatePart(Name = "Pressed State", Type = typeof(Storyboard))][TemplatePart(Name = "FocusVisualElement", Type = typeof(UIElement))][TemplatePart(Name = "Disabled State", Type = typeof(Storyboard))]public class Button : ButtonBase{// Summary://     Initializes a new instance of the Button class.public Button();// Summary://     Apply a template to the Button.protected override void OnApplyTemplate();//// Summary://     Called when the IsEnabled property changes.//// Parameters://   isEnabled://     New value of the IsEnabled property.protected override void OnIsEnabledChanged(bool isEnabled);}
}

[TemplatePart(Name = "Normal State", Type = typeof(Storyboard))] 这种东东是做什么用的 ， 其实这是一种契约 ， 是一种推荐的控件设计模式（只是推荐） ， 意思是告诉要来写ControlTemplate的用户 ， 你的ControlTemplate中需要有一个x:Name为“Normal State” , 类型为Storyboard ， 当然这个类型可以是继承来的， 为什么一定要包含这些契约规定的元素 ， 因为逻辑部分对这些东西进行了引用，它们将对控件的默认行为起着关键作用， 可以理解为这个控件的最基本元素 ， 是实现默认行为的最小集合， 自然，你的ControlTemplate中如果没有包含契约中的内容 ， 则相应的逻辑将无法实现。

所以说白了，就是提示用的.....这么写比较规范。