Silverlight Tip of the Day #24: How to Apply a XAML Template to a Class
Let’s say you have a class where you want to declare elements via a XAML template instead of dynamically creating them.
For example, the XAML to declare an image and add it to a canvas would look like this:
<Canvas x:Name="MyCanvas">
<Image x:Name="MyImage" Source="Grass.png"></Image>
</Canvas>
To do the same thing programmatically you would need to declare the following code:
Image myImage = new Image();
Uri uri = new Uri("Grass.png", UriKind.Relative);
ImageSource imgSrc = new System.Windows.Media.Imaging.BitmapImage(uri);
myImage.SetValue(Image.SourceProperty, imgSrc);
The way to do this via a template in a class is to first put the XAML into a string like this:
private const string _contentTemplate
= "<ControlTemplate xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\"" +
" xmlns:x=\"http://schemas.microsoft.com/winfx/2006/xaml\">" +
"<Image x:Name=\"MyImage\" Source=\"Grass.png\"></Image>" +
"</ControlTemplate>";
Your class will need to inherit from Control:
public class MyControl : Control
Now, in the constructor of your class you can load this template via the XamlReader.Load() method. You will need to add a using statement first to reference the namespace System.Windows.Markup;
public MyControl()
{
Template = (ControlTemplate)XamlReader.Load(_contentTemplate);
ApplyTemplate();
}
ApplyTemplate() is where you can get the elements that are in declared in your XAML code. Override the function OnApplyTemplate like this:
private _myImage;
public override void OnApplyTemplate()
{
_myImage = (Image)GetTemplateChild("MyImage");
}
Complete class:
using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Windows.Markup;
namespace MapEditor
{
public class MyImage : Control
{
Image _myImage = null;
private const string _contentTemplate
= "<ControlTemplate xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\"" +
" xmlns:x=\"http://schemas.microsoft.com/winfx/2006/xaml\">" +
"<Image x:Name=\"MyImage\" Source=\"Grass.png\"></Image>" +
"</ControlTemplate>";
public override void OnApplyTemplate()
{
_myImage = (Image)GetTemplateChild("MyImage");
}
public MyImage()
{
Template = (ControlTemplate)XamlReader.Load(_contentTemplate);
ApplyTemplate();
}
}
}
Thank you,
--Mike Snow
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