WPF TextBox change color on focus

Question

I try to change color on my input box when is focused.

First I declare input button:

<TextBox x:Name="usernameTextBox"
         HorizontalAlignment="Left"
         Height="23" 
         Margin="115,31,0,0"
         TextWrapping="Wrap"
         VerticalAlignment="Top"
         Width="277"
         GotFocus="usernameTextBox_GotFocus"/>

And below I try to add style for that textbox

<Style x:Key="usernameTextBox"
       TargetType="{x:Type TextBox}">
      <Style.Triggers>
          <Trigger Property="IsFocused"
                   Value="true">
               <Setter Property="Background"
                       Value="{StaticResource OnMouseOverColor}" />
         </Trigger>
    </Style.Triggers>
</Style>

Error:

Error 1 A value of type 'Style' cannot be added to a collection or dictionary of type 'UIElementCollection'. D:\\VS\\VIM\\VIM_WPF\\login.xaml 15 9 VIM_Wpf

Any other solution how to fix this?

Answer 1

Either you define your style as a resource (eg in your usercontrol / window's resources), and then do something like

<TextBox Style="{StaticResource theKeyOfYourStyle}" ..../>

or you explicitly set it in the TextBox:

<TextBox x:Name="usernameTextBox" HorizontalAlignment="Left" Height="23" Margin="115,31,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="277" GotFocus="usernameTextBox_GotFocus">
  <TextBox.Style>
    <Style TargetType="{x:Type TextBox}">
       <Style.Triggers>
         <Trigger Property="IsFocused" Value="true">
           <Setter Property="Background" Value="{StaticResource OnMouseOverColor}" />
         </Trigger>
       </Style.Triggers>
     </Style>
   </TextBox.Style>
</TextBox>