一、简单设置水印TextBox控件，废话不多说看代码：
<TextBox TextWrapping="Wrap" Margin="10" Height="69" Visibility="Visible"> <TextBox.Style> <Style TargetType="TextBox"> <Style.Triggers> <MultiTrigger> <MultiTrigger.Conditions> <Condition Property="IsFocused" Value="false"/> <Condition Property="Text" Value=""/> </MultiTrigger.Conditions> <Setter Property="Background"> <Setter.Value> <VisualBrush AlignmentX="Left" AlignmentY="Top" Stretch="None"> <VisualBrush.Visual> <TextBlock Padding="5 2" Background="Transparent" TextWrapping="Wrap" Height="40" Foreground="Silver">您的评价对网友有很重要的参考作用，请认真填<LineBreak/>写，谢谢合作!</TextBlock> </VisualBrush.Visual> </VisualBrush> </Setter.Value> </Setter> </MultiTrigger> </Style.Triggers> </Style> </TextBox.Style> </TextBox>
这里的style可以单独提出来，方便多处使用。
设置之后的效果如下：
二、扩展增强TextBox
有的时候会碰到TextBox里面需要添加按钮，或者TextBox需要设置圆角。这个时候就需要添加自定义控件，添加依赖属性来扩展功能了。
2.1 添加自定义控件TextBoxEx
代码如下：
public class TextBoxEx : TextBox { static TextBoxEx() { DefaultStyleKeyProperty.OverrideMetadata(typeof(TextBoxEx), new FrameworkPropertyMetadata(typeof(TextBoxEx))); } public TextBoxEx() { CommandBindings.Add(new CommandBinding(SearchClickCommand, delegate { SearchClick?.Invoke(this, null); })); } public static RoutedUICommand SearchClickCommand = new RoutedUICommand(nameof(SearchClickCommand), nameof(SearchClickCommand), typeof(RoutedUICommand)); public event EventHandler SearchClick; public string WaterMark { get { return (string)GetValue(WaterMarkProperty); } set { SetValue(WaterMarkProperty, value); } } public static readonly DependencyProperty WaterMarkProperty = DependencyProperty.Register("WaterMark", typeof(string), typeof(TextBoxEx), new PropertyMetadata(null)); public ImageSource Icon { get { return (ImageSource)GetValue(IconProperty); } set { SetValue(IconProperty, value); } } public static readonly DependencyProperty IconProperty = DependencyProperty.Register("Icon", typeof(ImageSource), typeof(TextBoxEx), new PropertyMetadata(null)); public new Brush BorderBrush { get { return (Brush)GetValue(BorderBrushProperty); } set { SetValue(BorderBrushProperty, value); } } public static readonly new DependencyProperty BorderBrushProperty = DependencyProperty.Register("BorderBrush", typeof(Brush), typeof(TextBoxEx), new PropertyMetadata(new SolidColorBrush(Color.FromRgb(234,234,234)))); public Brush MouseOverBorderBrush { get { return (Brush)GetValue(MouseOverBorderBrushProperty); } set { SetValue(MouseOverBorderBrushProperty, value); } } public static readonly DependencyProperty MouseOverBorderBrushProperty = DependencyProperty.Register("MouseOverBorderBrush", typeof(Brush), typeof(TextBoxEx), new PropertyMetadata(new SolidColorBrush(Color.FromRgb(79,173,216)))); public new Brush Background { get { return (Brush)GetValue(BackgroundProperty); } set { SetValue(BackgroundProperty, value); } } public static readonly new DependencyProperty BackgroundProperty = DependencyProperty.Register("Background", typeof(Brush), typeof(TextBoxEx), new PropertyMetadata(new SolidColorBrush(Color.FromRgb(106,103,90)))); public Brush MouseOverBackground { get { return (Brush)GetValue(MouseOverBackgroundProperty); } set { SetValue(MouseOverBackgroundProperty, value); } } public static readonly DependencyProperty MouseOverBackgroundProperty = DependencyProperty.Register("MouseOverBackground", typeof(Brush), typeof(TextBoxEx), new PropertyMetadata(Color.FromRgb(106,103,90))); public CornerRadius CornerRadius { get { return (CornerRadius)GetValue(CornerRadiusProperty); } set { SetValue(CornerRadiusProperty, value); } } public static readonly DependencyProperty CornerRadiusProperty = DependencyProperty.Register("CornerRadius", typeof(CornerRadius), typeof(TextBoxEx), new PropertyMetadata(new CornerRadius(0))); public IconDirection IconDirection { get { return (IconDirection)GetValue(IconDirectionProperty); } set { SetValue(IconDirectionProperty, value); } } public static readonly DependencyProperty IconDirectionProperty = DependencyProperty.Register("IconDirection", typeof(IconDirection), typeof(TextBoxEx), new PropertyMetadata(IconDirection.Right)); } public enum IconDirection { Left, Right }
2.2 设置TextBoxEx样式
<Style TargetType="{x:Type local:TextBoxEx}"> <Setter Property="Foreground" Value="#555558"/> <Setter Property="Background" Value="#6a675a"/> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type local:TextBoxEx}"> <Border x:Name="_border" CornerRadius="{TemplateBinding CornerRadius}" Padding="{TemplateBinding CornerRadius,Converter={StaticResource cornerRadiusToThickness} }" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" SnapsToDevicePixels="True"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition x:Name="columleft" Width="auto"/> <ColumnDefinition Width="*"/> <ColumnDefinition x:Name="columright" Width="auto"/> </Grid.ColumnDefinitions> <Image Source="{TemplateBinding Icon}" Cursor="Hand" Stretch="None" VerticalAlignment="Center" HorizontalAlignment="Center"> <i:Interaction.Triggers> <i:EventTrigger EventName="MouseLeftButtonUp"> <i:InvokeCommandAction Command="local:TextBoxEx.SearchClickCommand"/> </i:EventTrigger> </i:Interaction.Triggers> </Image> <ScrollViewer x:Name="PART_ContentHost" VerticalAlignment="Center" Foreground="{TemplateBinding Foreground}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" Grid.Column="1"/> <TextBlock x:Name="_txtWater" IsHitTestVisible="False" Margin="3 0 0 0" VerticalAlignment="Center" Foreground="#9f9f9f" Text="{TemplateBinding WaterMark}" Visibility="Hidden" Grid.Column="1"/> <Image Source="{TemplateBinding Icon}" Cursor="Hand" Stretch="None" Grid.Column="2" VerticalAlignment="Center" HorizontalAlignment="Center"> <i:Interaction.Triggers> <i:EventTrigger EventName="MouseLeftButtonUp"> <i:InvokeCommandAction Command="local:TextBoxEx.SearchClickCommand"/> </i:EventTrigger> </i:Interaction.Triggers> </Image> </Grid> </Border> <ControlTemplate.Triggers> <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Text}" Value=""> <Setter TargetName="_txtWater" Property="Visibility" Value="Visible" /> </DataTrigger> <Trigger Property="IsEnabled" Value="False"> <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/> </Trigger> <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=IconDirection}" Value="Left"> <Setter TargetName="columright" Property="Width" Value="0" /> </DataTrigger> <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=IconDirection}" Value="Right"> <Setter TargetName="columleft" Property="Width" Value="0" /> </DataTrigger> <Trigger Property="IsMouseOver" Value="True"> <Setter Property="BorderBrush" Value="{Binding MouseOverBorderBrush,RelativeSource={RelativeSource TemplatedParent}}"/> <Setter Property="Background" Value="{Binding MouseOverBackground,RelativeSource={RelativeSource TemplatedParent}}"/> </Trigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter> </Style>
这里面使用了一个转换器cornerRadiusToThickness，转换器的作用是当TextBox设置了圆角之后，保证TextBox里的内容不溢出圆角。WPF转换器的使用大家可以百度。
转换器的内容如下：
public class CornerRadiusToThickness : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { Thickness result = new Thickness(0); if (value is CornerRadius) { var tem = (CornerRadius)value; result = new Thickness(tem.TopLeft, 0, tem.TopRight, 0); } return result; } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotImplementedException(); } }
另外为了触发TextBox按钮的单击事件，添加了这个两个dll文件引用，Microsoft.Expression.Interactions.dll和System.Windows.Interactivity.dll。
在顶部定义 xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
2.3 引用方法
<local:TextBoxEx WaterMark="请输入搜索内容..." SearchClick="TextBoxEx_SearchClick" KeyDown="TextBoxEx_KeyDown" Background="#dfe1e3" VerticalAlignment="Center" MouseOverBackground="#dfe1e3" CornerRadius="13.5" IconDirection="Right" Icon="/Images/Title/search.png" Height="25" />
所有代码已经上传到github：https://github.com/caomfan/WpfDemo.git