WPF trouble applying a style to a textbox-CodePudding

I am a bit new to WPF and am in need of some assistance.. I am trying to setup a mouse over trigger event to change the 'style' of a textbox.. ie - when the user moves the mouse over the textbox, I want the border and background to change. So, after doing some digging around and reading here and there on this, I ended up with this:

<Window.Resources>
    <Style x:Key="WMCTextBoxStyle"  TargetType="{x:Type TextBox}" BasedOn="{StaticResource WMCTextBoxStyle}">
        <Setter Property="SnapsToDevicePixels" Value="True" />
        <Setter Property="OverridesDefaultStyle" Value="True" />
        <Setter Property="KeyboardNavigation.TabNavigation"  Value="None" />
        <Setter Property="AllowDrop" Value="False" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type TextBoxBase}">
                    <Border Name="Border1"
                            CornerRadius="3"
                            Padding="2"
                            BorderThickness="1"
                            Height="Auto" 
                            Width="auto" 
                            VerticalAlignment="Center" 
                            HorizontalAlignment="Center">
                        <Border.BorderBrush>
                            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                                <GradientStop Color="#FFA4B3C5" Offset="0"/>
                                <GradientStop Color="#FFA4B3C5" Offset="1"/>
                            </LinearGradientBrush>
                        </Border.BorderBrush>

                        <Border Name="Border2"
                            CornerRadius="0"
                            BorderThickness="1"
                            VerticalAlignment="Center" 
                            HorizontalAlignment="Center"
                            BorderBrush="Black">
                            <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>
                            <ScrollViewer Margin="0" x:Name="PART_ContentHost" />
                        </Border>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="Style" Value="{DynamicResource WMCTextBoxStyle}"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>

        </Setter>
    </Style>
</Window.Resources>

When I try to compile, I get the following two errors:

Error XDG0062 '{DependencyProperty.UnsetValue}' is not a valid value for the 'System.Windows.Controls.Control.Template' property on a Setter." in Line:12

Error XDG0062 Style object is not allowed to affect the Style property of the object to which it applies. in Line 19

I know that I am missing something basic on this, but not sure exactly how to get around it. When remove the --- out of the code, and then create a textbox and manually set the style, it works.. so I know that I am doing something wrong with the triggers... and I am sure it is something basic and 'newbie' ish...

any help would be appreciated.. :)

Here is the latest version

<Window.Resources>
    <Style x:Key="WMCTextBoxStyle"
       TargetType="TextBox">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type TextBoxBase}">
                    <Border x:Name="border"
                           Background="{TemplateBinding Background}"
                             BorderBrush="{TemplateBinding BorderBrush}"
                             BorderThickness="{TemplateBinding BorderThickness}"
                             SnapsToDevicePixels="True">
                        <ScrollViewer x:Name="PART_ContentHost"
                                    Focusable="false"
                                    HorizontalScrollBarVisibility="Hidden"
                                    VerticalScrollBarVisibility="Hidden" />

                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsEnabled"
                                Value="false">
                            <Setter Property="Opacity"
                                   TargetName="border"
                                    Value="0.56" />
                        </Trigger>
                        <Trigger Property="IsMouseOver"
                                   Value="True">

                            <Setter TargetName="border">
                                <Setter.Value>
                                    <Border Name="OuterBorder"
                                CornerRadius="3"
                                Padding="2"
                                BorderThickness="1"
                                Height="Auto" 
                                Width="auto" 
                                VerticalAlignment="Center" 
                                HorizontalAlignment="Center">
                                        <Border.BorderBrush>
                                            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                                                <GradientStop Color="#FFA4B3C5" Offset="0"/>
                                                <GradientStop Color="#FFA4B3C5" Offset="1"/>
                                            </LinearGradientBrush>
                                        </Border.BorderBrush>
                                        <Border Name="InnerBorder"
                                          CornerRadius="0"
                                            BorderThickness="1"
                                            VerticalAlignment="Center" 
                                             HorizontalAlignment="Center"
                                             BorderBrush="Black">
                                            <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>
                                    </Border>
                                </Setter.Value>
                            </Setter>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</Window.Resources>

CodePudding user response：

To understand how styles work, I recommend the following read (better don't skip it): How to create a style for a control (WPF .NET) (and Styles and templates in WPF).

"Error XDG0062 '{DependencyProperty.UnsetValue}' is not a valid value for the 'System.Windows.Controls.Control.Template' property on a Setter." in Line:12"

You can't base a Style n itself (doesn't make sense either - I'm sure this also creates a designer error, showing squiggles to indicate the exact erroneous piece of code).

<!-- Illegal 'BasedOn' reference to itself as base style -->
<Style x:Key="WMCTextBoxStyle" 
       BasedOn="{StaticResource WMCTextBoxStyle}">

"Error XDG0062 Style object is not allowed to affect the Style property of the object to which it applies. in Line 19"

You can't set the Style property from inside a Style that is the current value of the Style property. Apart from that it does not make sense to set the Style prooperty to itself.

<!-- Illegal modification of the Style property. Aside from that
     'WMCTextBoxStyle' is already the Style, otherwise the triggers are not in effect -->
<Setter Property="Style" Value="{DynamicResource WMCTextBoxStyle}"/>

When you define an explicit Style (a named Style), you must assign it explictly:

<TextBox Style="{StaticResource WMCTextBoxStyle}" />

The simplest Style to change the BorderThickness, Background and BorderBrush on mouse over is:

<Window>
  <Window.Resources>
    <Style x:Key="WMCTextBoxStyle"
           TargetType="TextBox">
      <Setter Property="Template">
        <Setter.Value>
          <ControlTemplate TargetType="{x:Type TextBoxBase}">
            <Border x:Name="border"
                    Background="{TemplateBinding Background}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    BorderThickness="{TemplateBinding BorderThickness}"
                    SnapsToDevicePixels="True">
              <ScrollViewer x:Name="PART_ContentHost"
                            Focusable="false"
                            HorizontalScrollBarVisibility="Hidden"
                            VerticalScrollBarVisibility="Hidden" />
            </Border>
            <ControlTemplate.Triggers>
              <Trigger Property="IsEnabled"
                       Value="false">
                <Setter Property="Opacity"
                        TargetName="border"
                        Value="0.56" />
              </Trigger>
              <Trigger Property="IsMouseOver"
                       Value="True">
                <Setter Property="BorderThickness"
                        Value="2" />
                <Setter Property="BorderBrush"
                        Value="OrangeRed" />
                <Setter Property="Background"
                        Value="PaleGreen" />
              </Trigger>
            </ControlTemplate.Triggers>
          </ControlTemplate>
        </Setter.Value>
      </Setter>
    </Style>
  </Window.Resources>

  <!-- Apply the Style -->
  <TextBox Style="{StaticResource WMCTextBoxStyle}" />
</Window>

If you are not interested in modifying the BorderBrush you can even skip the complete template and move the triggers to the Style.Triggers property.

CodePudding user response：

Here is the updated code:

<Window.Resources>
    <Style x:Key="WMCTextBoxStyle"
       TargetType="TextBox">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type TextBoxBase}">
                    <Border x:Name="border"
                             Background="{TemplateBinding Background}"
                             BorderBrush="{TemplateBinding BorderBrush}"
                             BorderThickness="{TemplateBinding BorderThickness}"
                             SnapsToDevicePixels="True">
                        <ScrollViewer x:Name="PART_ContentHost"
                                    Focusable="false"
                                    HorizontalScrollBarVisibility="Hidden"
                                    VerticalScrollBarVisibility="Hidden" />

                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsEnabled"
                                Value="false">
                            <Setter Property="Opacity"
                                   TargetName="border"
                                    Value="0.56" />
                        </Trigger>
                        <Trigger Property="IsMouseOver"
                                   Value="True">

                            <Setter TargetName="border">
                                <Setter.Value>
                                    <Border Name="OuterBorder"
                                CornerRadius="3"
                                Padding="2"
                                BorderThickness="1"
                                Height="Auto" 
                                Width="auto" 
                                VerticalAlignment="Center" 
                                HorizontalAlignment="Center">
                                        <Border.BorderBrush>
                                            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                                                <GradientStop Color="#FFA4B3C5" Offset="0"/>
                                                <GradientStop Color="#FFA4B3C5" Offset="1"/>
                                            </LinearGradientBrush>
                                        </Border.BorderBrush>
                                        <Border Name="InnerBorder"
                                          CornerRadius="0"
                                            BorderThickness="1"
                                            VerticalAlignment="Center" 
                                             HorizontalAlignment="Center"
                                             BorderBrush="Black">
                                            <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>
                                    </Border>
                                </Setter.Value>
                            </Setter>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</Window.Resources>

When I actually use it as a style for the textbox control, that is when I get the error message. Here is an example of how I am using it in a textbox:

    <TextBox x:Name="inner" Text=" Return To Previous Folder" Grid.Row="2" Foreground="white" FontSize="35"  Style="{DynamicResource WMCTextBoxStyle}" Grid.ColumnSpan="3" Margin="190,10,50,174" />

If you want/need the full form code, I can post that as well.