Non Visual Controls in Visual Studio Designer
While working in Visual Studio Designer, Following controls don’t show up on the designer, you can see the HTML for them though. These controls are called Non-Visual Controls. Some of them are:
SqlDataSource
AccessDataSource
ObjectDataSource
XMLDataSource
SiteMapDataSource
In order to view them on the designer surface, you have to check the "Non Visual Controls" property in View Menu of the Visual Studio.