Apply the ThumbnailAttribute to assign a toolbox icon to a custom WPF or Silverlight control.

The following steps show how to add an icon representing your control to a type.

1. Create a design-time metadata assembly for your custom control. For more information, see How to: Use the Metadata Store.

2. Add an image at the same folder hierarchy as the type you pass to the ThumbnailAttribute. Supported extensions and file types are BMP, GIF, JPG, JPEG and PNG.

   Different designer hosts use different image sizes for the toolbox icon. You can specify a different image for the WPF Designer and Expression Blend by specifying the ThumbnailAttribute in the host-specific metadata assemblies, *.VisualStudio.Design.dll and *.Expression.Design.dll.

   Expression Blend uses 24x24 for the large icon size and 12x12 for the small icon size. The WPF Designer uses 16x16.

3. In the Properties window, set the build action for the image to EmbeddedResource.

   Note:
   The project sub-folders affect the namespace in which embedded resources are found.

4. Use the metadata store to add the ThumbnailAttribute to your control’s class. You can reuse the same image across multiple types by applying the same ThumbnailAttribute to multiple controls.

   The ThumbnailAttribute is also used to find a default icon for types added to the Collection Editor or Sub-Properties Editor “new instance” functionality.

The following code example shows how to add the ThumbnailAttribute to a custom Silverlight control by using the MetadataStore.

public class Metadata : IRegisterMetadata
{
    public void Register()
    {
        AttributeTableBuilder builder = new AttributeTableBuilder();
        builder.AddCustomAttributes(typeof(Proseware.Core.Controls.ProseControl), 
        new ThumbnailAttribute(typeof(Metadata), "SLControlLibrary.Design. logo.gif"));
        MetadataStore.AddAttributeTable(builder.CreateTable());
    }
} 

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