WPF设置TextBox内容为空时的提示文字的两种方式

 1 <TextBox x:Name="TxtUserName1" Grid.Column="1" FontSize="18" TextChanged="TxtUserName1_TextChanged"
 2                              Foreground="#FFB4EEFF" Margin="1" BorderThickness="4" VerticalContentAlignment="Center">
 3                 <TextBox.Resources>
 4                     <VisualBrush x:Key="HintText" TileMode="None" Opacity="0.5" Stretch="None" AlignmentX="Left">
 5                         <VisualBrush.Visual>
 6                             <TextBlock Text="请输入用户名" Foreground="Gray"/>
 7                         </VisualBrush.Visual>
 8                     </VisualBrush>
 9                 </TextBox.Resources>
10                 <TextBox.Style>
11                     <Style TargetType="TextBox">
12                         <Style.Triggers>
13                             <Trigger Property="Text" Value="{x:Null}">
14                                 <Setter Property="Background" Value="{StaticResource HintText}"/>
15                             </Trigger>
16                             <Trigger Property="Text" Value="">
17                                 <Setter Property="Background" Value="{StaticResource HintText}"/>
18                             </Trigger>
19                         </Style.Triggers>
20                     </Style>
21                 </TextBox.Style>
22             </TextBox>

1 <Grid Grid.Row="3">
2             <TextBox x:Name="TxtUserName2" Grid.Column="1" FontSize="18" TextChanged="TxtUserName2_TextChanged"  Background="AliceBlue"
3                              Foreground="#FFB4EEFF" Margin="1" BorderThickness="4" VerticalContentAlignment="Center">
4             </TextBox>
5             <TextBlock Name="txtTip" Text="请输入用户名" Padding="10"></TextBlock>
6         </Grid>

1  private void TxtUserName2_TextChanged(object sender, TextChangedEventArgs e)
2         {
3             txtTip.Visibility = string.IsNullOrEmpty(TxtUserName2.Text) ? Visibility.Visible : Visibility.Hidden;
4         }