Assembly: System.Web.Extensions (in System.Web.Extensions.dll)
When the DataKeyNames property is set, the ListView control automatically creates a DataKey object for each item in the control. The DataKey object contains the values of the field or fields that are specified in the DataKeyNames property. The DataKey objects are then added to the control's collection.
You can use the SelectedDataKey property to retrieve the DataKey object for the currently selected item. You can also use the SelectedValue property to retrieve the data-key value for the currently selected item directly.
The following example shows how to use the property to determine the data-key values for the items in a ListView control. It also shows how to preserve the user selection based on a data item instead of the default behavior that uses the index.