DataControlBase.CustomUniqueValuesCommand Property

Gets or sets a command that populates a column’s Drop-down Filter with unique values.

Namespace: DevExpress.Xpf.Grid

Assembly: DevExpress.Xpf.Grid.v23.1.Core.dll

NuGet Package: DevExpress.Wpf.Grid.Core

Declaration

C#

public ICommand<UniqueValuesArgs> CustomUniqueValuesCommand { get; set; }

VB.NET

Public Property CustomUniqueValuesCommand As ICommand(Of UniqueValuesArgs)

Property Value

Type	Description
ICommand<UniqueValuesArgs>	A command that populates a column’s Drop-down Filter with unique values.

Remarks

Bind a command to the CustomUniqueValuesCommand property to maintain a clean MVVM pattern. The command works like a CustomUniqueValues event handler and allows you to specify a custom set of unique values in a View Model.

The GridControl executes the command bound to the CustomUniqueValuesCommand property before a user opens a column’s Drop-down Filter. This command allows you to manually specify filter values.

XAML

<dxg:GridControl ItemsSource="{Binding Products}" 
                 AutoGenerateColumns="AddNew" 
                 CustomUniqueValuesCommand="{Binding CustomUniqueValuesCommand}"/>

C#

using DevExpress.Mvvm;
using DevExpress.Mvvm.DataAnnotations;
using DevExpress.Mvvm.Xpf;
using DevExpress.Xpf.Data;

// ...

[Command]
public void CustomUniqueValues(UniqueValuesArgs args) {
    if (args.FieldName == "CategoryName") {

        // Synchronously:
        // Specify the UniqueValues / UniqueValuesAndCounts property.

        args.UniqueValuesAndCounts = GetProductsQueryCore()
            .GroupBy(x => x.CategoryName)
            .Select(x => new ValueAndCount(x.Key, x.Count()))
            .ToArray();

        // Asynchronously:
        // Specify the UniqueValuesAsync / UniqueValuesAndCountsAsync property.

        args.UniqueValuesAndCountsAsync = Task.Run(() => {
            return GetProductsQueryCore()
                .GroupBy(x => x.CategoryName)
                .Select(x => new ValueAndCount(x.Key, x.Count()))
                .ToArray();
        });
    }
}

VB.NET

Imports DevExpress.Mvvm
Imports DevExpress.Mvvm.DataAnnotations
Imports DevExpress.Mvvm.Xpf
Imports DevExpress.Xpf.Data

<Command>
Public Sub CustomUniqueValues(ByVal args As UniqueValuesArgs)
    If args.FieldName = NameOf(Product.ProductName) Then
        args.UniqueValues = ProductsDataModel.GetProducts()
            .GroupBy(Function(x) x.ProductName)
            .[Select](Function(x) x.Key)
            .ToArray()

        args.UniqueValuesAsync = Task.Run(Function() ProductsDataModel.GetProducts()
            .GroupBy(Function(x) x.ProductName)
            .[Select](Function(x) x.Key)
            .Cast(Of Object)()
            .ToArray())
    End If
End Sub

If your data source implements the IQueryable interface, you can use the GridQueryableExtensions.Distinct and GridQueryableExtensions.DistinctWithCounts methods from the DevExpress.Xpf.Grid.23.1.Extensions.dll library to obtain unique values.

C#

[Command]
public void CustomUniqueValues(UniqueValuesArgs args) {
    if (args.FieldName == "CategoryName") {
        args.UniqueValuesAndCountsAsync = Task.Run(() => {
            return GetProductsQueryCore().DistinctWithCounts(args.FieldName);
        }
    }
}

VB.NET

<Command>
Public Sub CustomUniqueValues(ByVal args As UniqueValuesArgs)
    If args.FieldName = "CategoryName" Then
        args.UniqueValuesAndCountsAsync = Task.Run(Function() GetProductsQueryCore().DistinctWithCounts(args.FieldName))
    End If
End Sub