Saving a WPF canvas as an image following MVVM Pattern

Question

I have a canvas, e.g. similar to this solution or many others using the ItemsControl.

Now I want a button which should be bound to an ICommand. This command should call a method of ViewModel class which can save the image. The saving method is clear, but how do I do the binding following the MVVM pattern?

Answer 1

You could pass the Canvas to the ViewModel's Save method using a CommandParameter

<Button Content="Save" 
        Command="{Binding SaveCanvasCommand}" 
        CommandParameter="{Binding ElenementName=myCanvas}" ?>

<Canvas x:Name="myCanvas">
   <!-- Stuff to save -->
</Canvas>

And somewhere in you ViewModel or Command you'd have

void SaveCanvasCommandExecute(object parameter)
{
    UIElement toSave = (UIElement)parameter;
    //.. You'd probably use RenderTargetBitmap here to save toSave.
}