The ContainerControlDesigner.AddDesignTimeCssAttributes(IDictionary) method adds a set of style attributes for the design-time representation of the control. The style attribute values are added to the styleAttributes collection, keyed by the style attribute name. For example, you can access the height value in the collection as styleAttributes["height"] for C# or styleAttributes("height") for Microsoft Visual Basic.

If the associated control is not derived from the System.Web.UI.WebControls.WebControl class, the ContainerControlDesigner.AddDesignTimeCssAttributes(IDictionary) method does not add attribute values to the styleAttributes collection.