VerticalAlignment="Stretch" for label inside canvas doesn't work - wpf

Question

How to use VerticalAlignment="Stretch" with a Label inside a Canvas? I'm trying to center the text "Cancel" in the button as in the code below. To use fixed height and width for the label isn't a desired option.
<Button Name="buttonCancel" Width="80" Height="40" IsCancel="True" Padding="0" HorizontalContentAlignment="Stretch" VerticalContentAlignment="Stretch">
<Canvas>
<Label Canvas.Top="0" Canvas.Left="0" Padding="0" FontSize="10">Esc</Label>
<Label VerticalContentAlignment="Center" HorizontalContentAlignment="Center" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">Cancel</Label>
</Canvas>
</Button>

Answer 1

Use a binding to the Canvas's ActualWidth:
<Canvas>
<Label Width="{Binding RelativeSource={RelativeSource AncestorType={x:Type Canvas}}, Path=ActualWidth}">...</Label>
</Canvas>
But as mentioned above, if you are interested in dynamic stretching layouts, the Canvas is not the ideal choice of control.

Answer 2

A Canvas does not perform any scaling layout of its contents; if you want to scale the contents, you could use Grid in this case, which will, by default, scale both Label elements to fill the Content space.

Answer 3

Assuming you need the canvas for other objects that are of a fixed nature, you could overlay the Canvas on a Grid, and then put the labels in the grid. You can put the labels before the canvas to make them background z-index (overwritten by canvas objects) or after the canvas to make them higher z-index (will overwrite canvas objects). For example:
<Button Name="buttonCancel" Width="80" Height="40" IsCancel="True" Padding="0" HorizontalContentAlignment="Stretch" VerticalContentAlignment="Stretch">
<Grid>
<Label Padding="0" FontSize="10">Esc</Label>
<Label VerticalContentAlignment="Center" HorizontalContentAlignment="Center" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">Cancel</Label>
<Canvas>
<!-- Your Canvas content here -->
</Canvas>
</Grid>
</Button>

Answer 4

Repeating my solution from the comments, since (a) you really don't want a Canvas and (b) it sounds like this solved your problems, so I'll make it an answer where it will be more visible to others.
Canvas is meant for fixed-pixel-size layouts, which is probably the least common case. You should replace your Canvas with a Grid as shown below, so that both Labels are laid out dynamically (and independently) within the available space:
<Grid>
<Label Padding="0" FontSize="10">Esc</Label>
<Label VerticalAlignment="Center" HorizontalAlignment="Center">Cancel</Label>
</Grid>