Change WPF button background image programmatically

Question

I'm trying to create a <Button/> with a png image for the background AND a background color.

Note: The png image source may not yet be known, so I can't just put them in the template.

I've got a Style that looks like this:

<Style x:Key="MyButton" TargetType="Button">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="Button">
                <Border CornerRadius="0">
                    <Image Margin="0" Source="/MyApp;component/Images/my-image.png" Stretch="None" />
                    <Border.Style>
                        <Style TargetType="{x:Type Border}">
                            <Setter Property="Background" Value="LimeGreen" />
                        </Style>
                    </Border.Style>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

which gives me a button with a png image on top of a solid LimeGreen background.

My MainWindow.xaml looks somewhat like this:

<Button Style="{StaticResource MyButton}" Click="btnMine_Click" /* some other props */ />

and the code behind it is like this:

private void btnMine_Click(object sender, RoutedEventArgs e)
{
    // TODO: change the image src on this button
    var myButton = sender as Button;

    // This won't work:
    // myButton.Border.Image.Source = getNewImageString();
}

How do I change the image source from /MyApp2;component/Images/my-image.png to something else?

Answer 1

Sigh, in Windows Forms it was literally one line. In WPF it looks like it will be several hundred.

That's because it was the ONLY thing you could place in a button in winforms. WPF is a true UI framework, not some random semi-deprecated dinosaur that only allows to do the default stuff (which by the way looks horrible).

Option 1: Place the Image as Button's Content:

If you just want to place an Image in the button, and nothing else, why not just do that?

        <Style TargetType="Button">
            <Setter Property="Background" Value="LimeGreen"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Button">
                        <Border Background="{TemplateBinding Background}">
                            <ContentPresenter ContentSource="Content"/>
                        </Border>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

Then:

     <Button>
        <!-- Background not set, defaults to what's set in the Style -->
        <Image Source="./ChessPieces/BlackKnight.png"/>
    </Button>
    <Button Background="Red">
        <Image Source="./ChessPieces/BlackBishop.png"/>
    </Button>
    <Button Background="Blue">
        <Image Source="./ChessPieces/BlackPawn.png"/>
    </Button>

    <!-- WPF's idea of "Dynamic" is not the same as win(hack)forms' -->
    <Button Background="White">
        <Image Source="{Binding SomeStringPropertyDefinedInAViewModel}"/>
    </Button>

Result:

Option 2 (not very elegant): Use the Tag Property:

If, in addition to the Image, you want to put something else inside the Button, you can resort to a somewhat hacky approach of putting the ImageSource in the Button's Tag property.

        <Style TargetType="Button">
            <Setter Property="Background" Value="LimeGreen"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Button">
                        <Border Background="{TemplateBinding Background}">
                            <StackPanel Orientation="Horizontal">
                                <Image Source="{Binding Tag, RelativeSource={RelativeSource TemplatedParent}}"
                                       Height="50" Width="50"/>
                                <ContentPresenter ContentSource="Content"/>
                            </StackPanel>
                        </Border>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

Then:

    <Button Tag="./ChessPieces/BlackKnight.png"
            Background="Blue"
            Foreground="White"
            Content="Some Text"/>

    <Button Tag="./ChessPieces/BlackBishop.png"
            Background="LightGray">
        <CheckBox Content="A CheckBox!" VerticalAlignment="Center"/>
    </Button>

Result:

Option 3: Use an Attached Property

Same as option 2, but using a property declared elsewhere, for example:

 <Button ButtonImage.Source="./ChessPieces/BlackBishop.png"
         <!-- etc -->

Option 4: Create a Custom Control:

Create a class (.cs file with no XAML) derived from Button and add a DependencyProperty to hold the image, then set the template to that and use that value.

Option 5: MVVM

Create a ButtonViewModel, or actually use a DelegateCommand declared in the ViewModel to bind the Button's properties.

Not an Option: Traverse the Visual Tree and change the Image.Source in code.

That's not something you will want to do. It's not a good approach at all.

I could go on forever, but I have to go to sleep. If you want me to elaborate on any of these approaches just let me know.

Answer 2

A few ways spring to mind:

1. Access the style at runtime and traverse it to find the image
2. Give the image a name and reference that at runtime and just change the source

The best solution I believe is to create a usercontrol and have the image source as a dependency property see: http://www.codeproject.com/Articles/224230/Exploring-the-use-of-Dependency-Properties-in-User

That way you'll have a ready-to-use "custom" control that supports what you're after and allows you to just reference it directly and use bindings, that way you avoid the messy solutions from using a style.

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After discussion and expansion on requirements, please see:

How can I access ResourceDictionary in wpf from C# code?