RadDropDownList fully supports binding to various data sources:
Data sources can support both hierarchical and non-hierarchical structures. RadDropDownList , however, only works with a flat structure - items cannot contain children.
The following properties and methods are used when binding RadDropDownList to a data source:
DataSource property - set to an instance of your data source. This is mandatory when binding RadDropDownList at runtime.
DataSourceID property - set to the ID of your data source. This is mandatory when binding RadDropDownList declaratively.
DataTextField property - field name from the data source to bind to the Text property.
DataValueField property - field name from the data source to bind to the Value property.
DataBind method - must be called after the aforementioned properties are set, when binding at runtime. This method is mandatory for binding at runtime.
If you need to map additional fields from the Data Source to properties of RadDropDownList item, the ItemDataBound event should be used. See Binding To ASP DataSource Components, for an example.
RadDropDownList exposes the AppendDataBoundItems property (set to False by default). If you bind the RadDropDownList using the DataBind method, all RadDropDownList items are automatically cleared.
Setting AppendDataBoundItems to True preserves the items that are already present in RadDropDownList. This lets you bind RadDropDownList to multiple data sources or use both unbound and bound modes.