Gets the data source component from the associated control container, resolved to a specific data member.
An object implementing an IEnumerable interface containing the design-time System.Web.UI.WebControls.BaseDataList.DataSource of the associated control, resolved to the System.Web.UI.WebControls.BaseDataList.DataMember parameter; 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, string) method to construct a data source from the object that is specified by the System.Web.UI.WebControls.BaseDataList.DataSource and System.Web.UI.WebControls.BaseDataList.DataMember properties of the associated control derived from the System.Web.UI.WebControls.BaseDataList class.