WPF案例：如何设计搜索框（自定义控件的原则和方法）

我们平时自定义WPF控件的方法有：Style，DataTemplate，ControlTemplate， DependencyProperty， CustomControl等几个方法。

按照优先顺序应该是从左到右。（所谓Style，这里仅包括Setter）

对于搜索框，其组成也就是TextBox+Button（清空），这里我们用CustomControl的方法比较合适。

1.创建SearchBox继承于TextBox，并声明2个Part属性， 表明此控件组成

     [TemplatePart(Name = "PART_SearchTextBox", Type = typeof(TextBox))]

     [TemplatePart(Name = "PART_ClearButton", Type = typeof(Button))]

      public class SearchBox : TextBox

2.创建2个子控件的Style， 注意ControlTemplate中的子控件命名和上述属性声明一致

<Style TargetType="{x:Type local:SearchBox}">
      <Setter Property="Template">   
         <Setter.Value>                
               <ControlTemplate TargetType="{x:Type local:SearchBox}">
                    <!-------------子控件PART_SearchTextBox,PART_ClearButton及其它设置--------------->
               </ControlTemplate>
          </Setter.Value>
      </Setter>
</Style>
3.如果在当前程序集里，必须放在.\Themes文件夹下; 必须在程序集的AssemblyInfo.cs里指定ThemeInfo（用来指定控件默认Style）
[assembly: ThemeInfo(
    ResourceDictionaryLocation.None, //where theme specific resource dictionaries are located
    //(used if a resource is not found in the page,
    // or application resource dictionaries)
    ResourceDictionaryLocation.SourceAssembly //where the generic resource dictionary is located
    //(used if a resource is not found in the page,
    // app, or any theme specific resource dictionaries)
)]

4.在自定义控件的实现中注册路由事件等等其它逻辑处理
比如：对子元素Clear按钮进行处理

       public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            Button btnClear = base.GetTemplateChild("PART_ClearButton") as Button;
            if (btnClear != null)
            {
               btnClear.Click += new RoutedEventHandler(OnClearButton_Click);
            }
        }

        private void OnClearButton_Click(Object sender, RoutedEventArgs e)
        {
            TextBox txtSearch = base.GetTemplateChild("PART_SearchTextBox") as TextBox;

            if (txtSearch!= null)
            {
               txtSearch.Text = String.Empty;
               txtSearch.Focus();
            }
        }