The ContainerControlDesigner.GetDesignTimeCssAttributes method returns a collection of style attributes for the design-time representation of the control.

To examine a style attribute value at design time for a control, use the style attribute name as a key to the returned collection. Style attribute values are stored as strings in the collection. 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.GetDesignTimeCssAttributes method returns an empty collection.