The C1HtmlHost can be populated in two ways:

• Use the SourceHtml property to specify an HTML string that should be displayed in the control. This option is useful if your application builds or loads the HTML content.
• Use the SourceUri property to specify the URL that will be displayed in the control. This option is useful if your application needs to display content that is already available at a given URL.

The C1HtmlHost control has an important requirement. In order to display the HTML content within the Silverlight plug-in, the plug-in must have its Windowless property set to True. If you run the application now, you will see an error message that notes:

The control cannot modify the properties of the plug-in, the page author must do that instead. To make the necessary change, open the page that creates the plug-in and add a line to set the Windowless property to True. For details see Windowless Mode.