# DelegateGroupDescriptor

The difference between the `DelegateGroupDescriptor` and the [`PropertyGroupDescriptor`](https://www.telerik.com/winui/documentation/controls/raddatagrid/grouping/raddagagrid-propertygroupdescriptor) is that the `DelegateGroupDescriptor` groups data by a custom key, while the `PropertyGroupDescriptor` groups by a defined key, which is a property from our model.

## Adding a DelegateGroupDescriptor

To use a `DelegateSortDescriptor`, create a class that implements the `IKeyLookup` interface which will return the key you want to group by. Then, you need to add the `DelegateGroupDescriptor` to the `GroupDescriptors` collection and set its `KeyLookUp` property as shown in the following example. The DataGrid is populated with data in the same manner as demonstrated in the [**Populate the DataGrid with Data** example from the PropertyGroupDescriptor article](https://www.telerik.com/winui/documentation/controls/raddatagrid/grouping/raddagagrid-propertygroupdescriptor).

#### **Define the DataGrid in XAML**

```XAML
<Grid xmlns:grid="using:Telerik.UI.Xaml.Controls.Grid"
	  xmlns:dataCore="using:Telerik.Data.Core">
	<grid:RadDataGrid Width="600" Height="460" x:Name="grid">
		<grid:RadDataGrid.GroupDescriptors>
			<dataCore:DelegateGroupDescriptor>
				<dataCore:DelegateGroupDescriptor.KeyLookup>
					<local:CustomIKeyLookup/>
				</dataCore:DelegateGroupDescriptor.KeyLookup>
			</dataCore:DelegateGroupDescriptor>
		</grid:RadDataGrid.GroupDescriptors>
	</grid:RadDataGrid>
</Grid>
```

The following example demonstrates the implementation of the `IKeyLookup` interface. The `GetKey` method will receive an instance of our custom object. In this case, you will group the grid items by the first letter of a city.

#### **Define the CustomIKeyLookup Class**

```C#
public class CustomIKeyLookup : IKeyLookup
{
	public object GetKey(object instance)
	{
		return (instance as Data).City[0];
	}
}
```

**Grouped RadDataGrid**

![WinUI Delegate Group Descriptor](https://www.telerik.com/winui/documentation/assets/05818c57575041d0f9bed265082e16af/delegategroupdescriptor.png)

## See Also

* [PropertyGroupDescriptor](https://www.telerik.com/winui/documentation/controls/raddatagrid/grouping/raddagagrid-propertygroupdescriptor)