<UserControl x:Class="WpfApplication18.SearchControl"
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
 xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
 mc:Ignorable="d" MinHeight="30" MinWidth="150" Background="Transparent"
 d:DesignHeight="30" d:DesignWidth="150">
 <Grid>
 <Grid.ColumnDefinitions>
 <ColumnDefinition Width="15"></ColumnDefinition>
 <ColumnDefinition Width="*"></ColumnDefinition>
 <ColumnDefinition Width="36"></ColumnDefinition>
 </Grid.ColumnDefinitions>
 <Rectangle Grid.Column="0" Grid.ColumnSpan="3" Fill="LightGray" RadiusX="15" RadiusY="15" Opacity="0.8"></Rectangle>
 
 <TextBox x:Name="TbxInput" Grid.Column="1" KeyDown="TbxInput_OnKeyDown">
 <TextBox.Template>
 <ControlTemplate TargetType="TextBox">
 <Grid>
 <TextBlock x:Name="Uc_TblShow" Text="請輸入..." Foreground="Gray" Opacity="0.5" VerticalAlignment="Center" Visibility="Collapsed"></TextBlock>
 <TextBox x:Name="Uc_TbxContent" Foreground="Gray" Background="Transparent" VerticalAlignment="Center" VerticalContentAlignment="Center" BorderThickness="0"
 Text="{Binding ElementName=TbxInput,Path=Text,Mode=TwoWay}" FontSize="18"></TextBox>
 </Grid>
 <ControlTemplate.Triggers>
 <Trigger SourceName="Uc_TbxContent" Property="Text" Value="">
 <Setter TargetName="Uc_TblShow" Property="Visibility" Value="Visible"></Setter>
 </Trigger>
 <Trigger SourceName="Uc_TbxContent" Property="IsFocused" Value="True">
 <Setter TargetName="Uc_TblShow" Property="Visibility" Value="Collapsed"></Setter>
 </Trigger>
 </ControlTemplate.Triggers>
 </ControlTemplate>
 </TextBox.Template>
 </TextBox>
 
 <Button x:Name="BtnSearch" Grid.Column="2" Click="BtnSearch_OnClick" Cursor="Hand">
 <Button.Template>
 <ControlTemplate TargetType="Button">
 <Grid>
 <Image x:Name="Uc_Image" Source="1181298.png" Height="20" Width="20"></Image>
 <ContentPresenter></ContentPresenter>
 </Grid>
 <ControlTemplate.Triggers>
 <Trigger Property="IsMouseOver" Value="true">
 <Setter TargetName="Uc_Image" Property="Height" Value="25"></Setter>
 <Setter TargetName="Uc_Image" Property="Width" Value="25"></Setter>
 </Trigger>
 </ControlTemplate.Triggers>
 </ControlTemplate>
 </Button.Template>
 </Button>
 </Grid>
</UserControl> 

 public partial class SearchControl : UserControl
 {
 public SearchControl()
 {
 InitializeComponent();
 }

 public event EventHandler<SearchEventArgs> OnSearch; 
 private void BtnSearch_OnClick(object sender, RoutedEventArgs e)
 {
 ExeccuteSearch();
 }

 private void TbxInput_OnKeyDown(object sender, KeyEventArgs e)
 {
 ExeccuteSearch();
 }

 private void ExeccuteSearch()
 {
 if (OnSearch!=null)
 {
 var args=new SearchEventArgs();
 args.SearchText = TbxInput.Text;
 OnSearch(this, args);
 }
 }
 }
 public class SearchEventArgs : EventArgs
 {
 public string SearchText { get; set; }
 }