PagedAsyncSource.GetUniqueValues Event

Allows you to get unique values.

Namespace: DevExpress.Xpf.Data

Assembly: DevExpress.Xpf.Core.v24.1.dll

NuGet Package: DevExpress.Wpf.Core

Declaration

C#

public event EventHandler<GetUniqueValuesAsyncEventArgs> GetUniqueValues

VB.NET

Public Event GetUniqueValues As EventHandler(Of GetUniqueValuesAsyncEventArgs)

Event Data

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

Property	Description
Filter	Gets the GridControl‘s filtering. Inherited from GetUniqueValuesEventArgsBase.
PropertyName	Gets the property name. Inherited from GetUniqueValuesEventArgsBase.
Result	Gets or sets the result of the get unique values operation (only values).
ResultWithCounts	Gets or sets the result of the get unique values operation (values and their counts).

Remarks

View Example: How to Bind to PagedAsyncSource

Handle the GetUniqueValues event to show unique values in a column’s drop-down filter. You can also show counts of these values.

To show only unique values, get a list of these values and specify the GetUniqueValuesAsyncEventArgs.Result property.

To show unique values with their counts, get a list of these values with counts and specify the GetUniqueValuesAsyncEventArgs.ResultWithCounts property.

C#

source.GetUniqueValues += (o, e) => {
    if (e.PropertyName == "User") {
        e.ResultWithCounts = Task.Run(() => {
            return GetIssueDataQueryable().DistinctWithCounts(e.PropertyName);
        });
    } 
    e.Result = Task.Run(() => {
        return GetIssueDataQueryable().Distinct(e.PropertyName);
    });
};

VB.NET

AddHandler source.GetUniqueValues, Sub(o, e)
    If e.PropertyName = "User" Then
        e.ResultWithCounts = Task.Run(Function()
            Return GetIssueDataQueryable().DistinctWithCounts(e.PropertyName)
        End Function)
    End If
    e.Result = Task.Run(Function()
        Return GetIssueDataQueryable().Distinct(e.PropertyName)
    End Function)
End Sub 

In the code sample above, a data source implements the IQueryable interface. You can use the GridQueryableExtensions.Distinct and GridQueryableExtensions.DistinctWithCounts methods from the DevExpress.Xpf.Grid.24.1.Extensions.dll library to obtain unique values.

If you want to maintain a clean MVVM pattern and process unique values in a ViewModel, create a command and bind it to the PagedAsyncSource.GetUniqueValuesCommand property.

Related GitHub Examples

The following code snippet (auto-collected from DevExpress Examples) contains a reference to the GetUniqueValues event.

Note

The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.

C#

wpf-data-grid-bind-to-pagedasyncsource/CS/PagedAsyncSourceSample/MainWindow.xaml.cs#L26

source.GetUniqueValues += (o, e) => {
    if(e.PropertyName == "Priority") {

VB.NET

wpf-data-grid-bind-to-pagedasyncsource/VB/PagedAsyncSourceSample/MainWindow.xaml.vb#L19

AddHandler source.FetchPage, Sub(o, e) e.Result = FetchRowsAsync(e)
AddHandler source.GetUniqueValues, Sub(o, e)
    If Equals(e.PropertyName, "Priority") Then