Friday, March 14, 2008

Dynamically load an image in Silverlight 2.0 Beta

[This was originally posted at]

You can easily dynamically load images in Silverlight. given a relative url, you can convert that to an absolute url, and then to an ImageSource, and then use that to set an image. Here's a sample method that takes the relative path, the parent canvas that we'll add the image too, and an x-y point:


    private void AddImage(string strRelativeImagePath, Canvas myCanvas, Point p)
      //Convert from RelativePath to AbsolutePath to Uri to ImageSource
      string strFullUrl = GetAbsoluteUrl(strRelativeImagePath);
      Uri u = new Uri(strFullUrl, UriKind.Absolute);
      System.Windows.Media.Imaging.BitmapImage b = new System.Windows.Media.Imaging.BitmapImage(u);

      //Create the image here
      Image img = new Image();
      img.Source = b;
      img.SetValue(Canvas.LeftProperty, p.X);
      img.SetValue(Canvas.TopProperty, p.Y);
      //set other properties here...

      //now add to a canvas:


And just call it like so:


    AddImage("MyImage.png", this.parentCanvas, new Point(100, 50));


Note some changes from the 1.1 Alpha:

  • Image.Source is no longer just a string url, but rather a strongly-typed class. You need to create an ImageSource object first, such as by instantiating a Bitmap image (this allows other image types, like png, not just bmp).

  • The relative-to directory has changed, such that it's easiest to just convert to an absolute url. When you directly add this to the page, it works fine, but if you add it to a userControl from another class library, then it doesn't. Just using absolute urls makes it work (hence the GetAbsoluteUrl method I blogged about yesterday).

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