Dependency Property Generator
       by kirupa  |  29 March 2009

This site has a fair number of articles on dependency properties, but at the end of the day, they are still really hard to write. Remembering the syntax and making sure the C# equivalent of the i's and t's are dotted and crossed is very hard - even for experienced users.

To make this tedious task easier, I've written a small app that will create Dependency Properties for you as long as you give it the type, owning class, and property name. The app can be found below:

Get Microsoft Silverlight

If you are a reader of my blog, the above application should be old news to you. What will be new is the information on how to actually use the app and integrate its output into your own project.

Using the Dependency Property Generator
This little app asks for three pieces of information. First, you will be asked to enter your Property Name. This is the name you want to give your dependency property so that you can use it later on. To look at it another way, this is the value that you will see in the Properties Inspector of either Expression Blend or Visual Studio.

The next piece of information you will be asked is the Property Type. Your property type represents what form the data you store in the dependency property will be taking. Example values include string, double, int, MyCustomType, List, etc.

Finally, you will be asked the Owning Class Name. Your dependency property will be living inside something. This something is a class that you paste your dependency property code into. For example, let's look the code for a simple user control that I just created in Expression Blend:

using System;
using System.Collections.Generic;
using System.Net;
using System.Windows;
using System.Windows.Controls;
 
namespace DeepZoomProject
{
public partial class CustomPage : UserControl
{
public CustomPage()
{
InitializeComponent();
}
}
}

This user control's name is CustomPage, and my dependency property will live inside this usercontrol. This name is also the class name, so therefore, my Owning Class Name in this case will be CustomPage.

Integrating your Dependency Property
To close this example out, let's say I want to create a dependency property. My property will be called CustomName, its type will be string, and its owning class is CustomPage. I hit the Generate Code button, and out pops the following:

public string CustomName
{
get { return (string)GetValue(CustomNameProperty); }
set { SetValue(CustomNameProperty, value); }
}
 
public static readonly DependencyProperty CustomNameProperty = DependencyProperty.Register("CustomName", typeof(string), typeof(CustomPage), new PropertyMetadata("",CustomNameChanged));
 
private static void CustomNameChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
// Code for dealing with your property changes
}

Pasting the above into my CustomPage class, I get the following:

using System;
using System.Collections.Generic;
using System.Net;
using System.Windows;
using System.Windows.Controls;
 
namespace DeepZoomProject
{
public partial class CustomPage : UserControl
{
public string CustomName
{
get { return (string)GetValue(CustomNameProperty); }
set { SetValue(CustomNameProperty, value); }
}
 
public static readonly DependencyProperty CustomNameProperty = DependencyProperty.Register("CustomName", typeof(string), typeof(CustomPage), new PropertyMetadata("",CustomNameChanged));
 
private static void CustomNameChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
// Code for dealing with your property changes
}
 
public CustomPage()
{
InitializeComponent();
}
}
}

Notice that I pasted my dependency property code inside the area defined by my CustomPage class. The most common mistake is that you paste it outside your owning class's boundaries. Don't do that unless you want to see a build error or your dependency property not working.

That is all there is to filling in the three values, getting the code for your dependency property, and then simply pasting the code into the class you want the property to be exposed on.

Setting Default Values
The final detail is the default value that your dependency property may require. Currently, outside of string, double, and int types, I do not specify a default value for your dependency property. The reason is that each type will have its own unique way of specifying a default value for itself.

The default value is specified in the line defining your dependency property identifier:

public static readonly DependencyProperty CustomNameProperty = DependencyProperty.Register("CustomName", typeof(string), typeof(CustomPage), new PropertyMetadata("",CustomNameChanged));

More specifically, look in your PropertyMetadata constructor: new PropertyMetadata("",CustomNameChanged));

If there are two arguments, the first argument specifies the default value. For property types other than string, int, and double, you will not see two arguments. The only argument you see will be for the property changed callback, so insert your default value as the first argument to your PropertyMetadata constructor.


If you have a question about this or any other topic, the easiest thing is to drop by our forums where a bunch of the friendliest people you'll ever run into will be happy to help you out!

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