WPF Textbox Template assistance - wpf

Question

I am working on setting up a template for a textbox - and I am running into an issue with setting up the style for the box and am hoping for some assistance. Here is what I have so far:
---
<Window.Resources>
<Style TargetType="{x:Type TextBox}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBoxBase}">
<Border x:Name="Border">
<ScrollViewer x:Name="PART_ContentHost" Focusable="false" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden"/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter TargetName="Border">
<Setter.Value>
<Border BorderThickness="1" BorderBrush="Black" CornerRadius="0">
<Border.Background>
<RadialGradientBrush GradientOrigin="0.225,-0.616" RadiusY="0.863" RadiusX="0.757">
<GradientStop Color="#EEFFFFFF"/>
<GradientStop Color="#00FFFFFF" Offset="0.696"/>
</RadialGradientBrush>
</Border.Background>
</Border>
</Setter.Value>
</Setter>
</Trigger>
<Trigger Property="IsKeyboardFocused" Value="True">
</Trigger>
<Trigger Property="IsKeyboardFocused" Value="False">
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
---
When I try to compile this, I get a message stating:
Severity Code Description Project File Line Suppression State
Error MC3000 'The 'Setter' start tag on line 22 position 34 does not match the end tag of 'Trigger'. Line 35, position 31.' XML is not valid.
Anyone have any idea on what I missed here or am doing wrong? I think that I have closed all of the lines correctly.

Answer 1

The setter isn't working quite how you think it is. You're currently creating a border in your template and giving it an x:Name="Border", but then trying to overwrite it in the trigger, with the assumption that it will replace the existing border altogether:
<Setter TargetName="Border">
<Setter.Value>
<Border BorderThickness="1" BorderBrush="Black" CornerRadius="0">
That's not how setters work. Setters need three things:
A reference to an object that you want to modify (although in some cases this is implied).
The name of a property of that object that you wish to modify.
The new value for that property.
You're only providing 1 and 3, hence the error. Instead of trying to replace the border you have to instead modify the properties of the existing border:
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter TargetName="Border" Property="BorderThickness" Value="1" />
<Setter TargetName="Border" Property="BorderBrush" Value="Black" />
<Setter TargetName="Border" Property="CornerRadius" Value="0" />
<Setter TargetName="Border" Property="Background">
<Setter.Value>
<RadialGradientBrush GradientOrigin="0.225,-0.616" RadiusY="0.863" RadiusX="0.757">
<GradientStop Color="#EEFFFFFF"/>
<GradientStop Color="#00FFFFFF" Offset="0.696"/>
</RadialGradientBrush>
</Setter.Value>
</Setter>
</Trigger>
</ControlTemplate.Triggers>
In practice you'd typically wrap all these up in their own style and apply that instead to keep the code clean, but that's an implementation detail.
If you really do want to replace the actual border object then there are ways to do it (e.g. by changing the template itself), but in most cases the above should suffice.