Passing parameters to a template

Question

Hi,

Say I have defined a button with rounded corners.

<Style x:Key="RoundButton" TargetType="Button">
 <!-- bla bla -->
 <Setter Property="Template">
  <Setter.Value>
   <ControlTemplate TargetType="Button">
    <Border CornerRadius="0,5,5,0" />
    <!-- bla bla -->
   </ControlTemplate>
  </Setter.Value>
 </Setter>
</Style>

I it possible that the user of this button can specify the CornerRadius? Can I use a TemplateBinding? But where should I bind to? (to Tag?)

Answer 1

In order to use a TemplateBinding, there must be a property on the templated control (Button, in this case). Button does not have a CornerRadius or equivalent property, so your options are:

• hard code the value in the template
• Hijack another property (such as Tag) to store this information. This is quicker, but lacks type safety, is harder to maintain, and prevents other uses of that property.
• Subclass Button and add the propery you need, then provide a template for that subclass. This takes a little longer but yields a much nicer experience for consumers of your control.

HTH, Kent

Answer 2

In addition to Kent's suggestions, you could also create an attached property to define the CornerRadius on the button, and bind to that property in the template

Answer 3

The button type doesn't have a property for CornerRadius, so templating this won't be possible. I think the easiest way is creating a new class which inherits from Button and add a new dependency property for the CornerRadius. Like this:

using System.Windows;
using System.Windows.Controls;

namespace WpfApplication3
{
    public class RoundedButton:Button
    {
        public CornerRadius CornerRadius
        {
            get { return (CornerRadius) GetValue(CornerRadiusProperty); }
            set { SetValue(CornerRadiusProperty, value); }
        }
        public static readonly DependencyProperty CornerRadiusProperty =
            DependencyProperty.Register("CornerRadius", typeof (CornerRadius), 
            typeof (RoundedButton), new UIPropertyMetadata());
    }
}

In xaml you can use it like:

<Local:RoundedButton 
    Style="{DynamicResource RoundButton}" 
    Width="64" Height="32" 
    Content="Hello" 
    CornerRadius="1,5,10,5" 
    Background="#FF9CFFD5" />

A template binding to the CornerRadius will work without a problem now.