# DataBinding Overview

**RadDropDownList** fully supports binding to various data sources:

* [Array, ArrayList](https://www.telerik.com/products/aspnet-ajax/documentation/controls/dropdownlist/databinding/server-side-binding-/binding-to-array-or-arraylist)

* [DataTable, DataSet, DataView](https://www.telerik.com/products/aspnet-ajax/documentation/controls/dropdownlist/databinding/server-side-binding-/binding-to-datatable)

* [All ASP DataSource types](https://www.telerik.com/products/aspnet-ajax/documentation/controls/dropdownlist/databinding/server-side-binding-/binding-to-asp-datasource-components)

* [OData](https://www.telerik.com/products/aspnet-ajax/documentation/controls/dropdownlist/databinding/client-side-binding/binding-to-odata)

> note Data sources can support both hierarchical and non-hierarchical structures. **RadDropDownList** , however, only works with a flat structure - items cannot contain children.

## Databinding Properties and Methods

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.

> note 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](https://docs.telerik.com/devtools/aspnet-ajax/controls/dropdownlist/databinding/server-side-binding-/binding-to-asp-datasource-components#binding-to-asp-datasource-components), for an example.

## Appending Data Bound Items

**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.