DataControlBase.CustomUniqueValues Event

Allows you to specify unique values displayed within a column’s Drop-down Filter.

Namespace: DevExpress.Xpf.Grid

Assembly: DevExpress.Xpf.Grid.v21.2.Core.dll

NuGet Package: DevExpress.Wpf.Grid.Core

Declaration

C#

public event CustomUniqueValuesEventHandler CustomUniqueValues

VB.NET

Public Event CustomUniqueValues As CustomUniqueValuesEventHandler

Event Data

The CustomUniqueValues event's data class is CustomUniqueValuesEventArgs. The following properties provide information specific to this event:

Property	Description
AsyncCompleted	Gets an AsyncCompletedHandler delegate referencing a method that should be executed after the operation is completed.
Column	Gets a column for which a drop-down filter is shown.
Filter	Gets the current filter.
Handled	Gets or sets a value that indicates the present state of the event handling for a routed event as it travels the route. Inherited from RoutedEventArgs.
IncludeFilteredOut	Gets whether a drop-down filter’s values are displayed with ignoring filters by other columns.
OriginalSource	Gets the original reporting source as determined by pure hit testing, before any possible Source adjustment by a parent class. Inherited from RoutedEventArgs.
RoundDateTime	Gets or sets whether to ignore time values when you filter by DateTime values.
RoutedEvent	Gets or sets the RoutedEvent associated with this RoutedEventArgs instance. Inherited from RoutedEventArgs.
Source	Gets a control (GridControl or TreeListControl) that raised the event.
UniqueValues	Gets or sets unique values.
UniqueValuesAndCounts	Gets or sets unique values and their counts.
UniqueValuesAndCountsAsync	Gets or sets a task that allows you to asynchronously return unique values and their counts.
UniqueValuesAsync	Gets or sets a task that allows you to asynchronously return unique values.

The event data class exposes the following methods:

Method	Description
InvokeEventHandler(Delegate, Object)	When overridden in a derived class, provides a way to invoke event handlers in a type-specific way, which can increase efficiency over the base implementation. Inherited from RoutedEventArgs.
OnSetSource(Object)	When overridden in a derived class, provides a notification callback entry point whenever the value of the Source property of an instance changes. Inherited from RoutedEventArgs.

Remarks

The CustomUniqueValues event fires before a column’s drop-down filter is populated with unique column values. This event allows you to manually specify filter values.

Xaml

<dxg:GridControl Name="gridControl" ItemsSource="{Binding Products}"
                 CustomUniqueValues="gridControl_CustomUniqueValues">
    <dxg:GridControl.Columns>
        <dxg:GridColumn FieldName="ProductName" IsSmart="True"/>
        <dxg:GridColumn FieldName="CategoryName" IsSmart="True"/>
    </dxg:GridControl.Columns>
    <dxg:GridControl.View>
        <dxg:TableView/>
    </dxg:GridControl.View>
</dxg:GridControl>

C#

void gridControl_CustomUniqueValues(object sender, CustomUniqueValuesEventArgs e) {
    if (e.Column.FieldName == "CategoryName") {
        e.Handled = true;

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

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

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

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

VB.NET

Private Sub gridControl_CustomUniqueValues(ByVal sender As Object, ByVal e As CustomUniqueValuesEventArgs)
    If e.Column.FieldName = "CategoryName" Then
        e.Handled = True
        e.UniqueValuesAndCounts = GetProductsQueryCore()
            .GroupBy(Function(x) x.CategoryName)
            .[Select](Function(x) New ValueAndCount(x.Key, x.Count()))
            .ToArray()


        e.UniqueValuesAndCountsAsync = Task.Run(Function() 
            GetProductsQueryCore()
                .GroupBy(Function(x) x.CategoryName)
                .[Select](Function(x) New ValueAndCount(x.Key, x.Count()))
                .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.21.2.Extensions.dll library to obtain unique values.

C#

void gridControl_CustomUniqueValues(object sender, CustomUniqueValuesEventArgs e) {
    if (e.Column.FieldName == "CategoryName") {
        e.Handled = true;
        e.UniqueValuesAndCountsAsync = Task.Run(() => {
            return GetProductsQueryCore().DistinctWithCounts(e.Column.FieldName);
        }
    }
}

VB.NET

Private Sub gridControl_CustomUniqueValues(ByVal sender As Object, ByVal e As CustomUniqueValuesEventArgs)
    If e.Column.FieldName = "CategoryName" Then
        e.Handled = True
        e.UniqueValuesAndCountsAsync = Task.Run(Function() 
            GetProductsQueryCore().DistinctWithCounts(e.Column.FieldName))
    End If
End Sub 

If you want to maintain a clean MVVM pattern and specify a custom set of unique values in a View Model, create a command and bind it to the CustomUniqueValuesCommand property.