Two Help Classes for WPF Regarding Design

Introduction

This article shows a combination of two helper classes I wrote for WPF.

Background

For various reasons, I needed to set values to an element only to be shown in the Designer. This is done by the first class. The second class is used by the first to check whether code is running under the Designer.

Set a value to a control only in Design mode

Can you set a value to the DependencyProperty of a DependencyObject in Design mode? Using a custom MarkupExtension, you can. Here is the implementation:

[ContentProperty("Value")]
public class DesignTimeDummy : MarkupExtension
{
    public DesignTimeDummy()
    {
    }

    public object Value { get; set; }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        if (Helpers.Designer.InDesignMode)
        {
            return Value;
        }

        return DependencyProperty.UnsetValue;
    }
}

Here are two examples for the XAML code:

<Button Style="{DynamicResource styleName}" 
   Content="{CoreME:DesignTimeDummy Value=DesignContentValue}"/>

or

<Button Style="{DynamicResource styleName}" >
<Button.Content>
<CoreME:DesignTimeDummy>
Dummy </CoreME:DesignTimeDummy>
</Button.Content>
</Button>

where CoreME is an xmlns defined namespace shortcut.

Check to see if it is in Design mode

The above code uses this class:

public static class Designer
{
    private static DependencyObject dummy = new DependencyObject();
    public static bool InDesignMode
    {
        get { return DesignerProperties.GetIsInDesignMode(dummy); }
    }
}

Hope you find them useful.

Blog links

• http://sarafianalex.wordpress.com/2008/06/14/set-a-value-to-a-control-only-in-design-mode/
• http://sarafianalex.wordpress.com/2008/06/14/in-design-mode/