An object implementing an IEnumerable interface containing the design-time System.Web.UI.WebControls.BaseDataList.DataSource property of the associated control; otherwise, null if a data source is not found.
The BaseDataListDesigner.GetSelectedDataSource method uses the System.Web.UI.Design.DesignTimeData.GetSelectedDataSource(System.ComponentModel.IComponent, string) method to construct a data source from the object that is specified by the System.Web.UI.WebControls.BaseDataList.DataSource property of the associated control derived from the System.Web.UI.WebControls.BaseDataList class.