wpf-devexpress-dot-xpf-dot-data-dot-infiniteasyncsource.md
Allows you to get unique values.
Namespace : DevExpress.Xpf.Data
Assembly : DevExpress.Xpf.Core.v25.2.dll
NuGet Package : DevExpress.Wpf.Core
public event EventHandler<GetUniqueValuesAsyncEventArgs> GetUniqueValues
Public Event GetUniqueValues As EventHandler(Of GetUniqueValuesAsyncEventArgs)
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). |
View Example: How to Bind to InfiniteAsyncSource
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.
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);
});
};
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.25.2.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 InfiniteAsyncSource.GetUniqueValuesCommand property.
The following code snippets (auto-collected from DevExpress Examples) contain references 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.
wpf-data-grid-bind-to-custom-service-with-restrictions/CS/MainWindow.xaml.cs#L27
source.GetUniqueValues += (o, e) => {
e.Result = GetUniqueValuesAsync(e.PropertyName);
wpf-data-grid-use-virtual-sources-to-bind-to-in-memory-data/CS/MainWindow.xaml.cs#L37
source.GetUniqueValues += (o, e) => {
if(e.PropertyName == "Priority") {
wpf-data-grid-bind-to-infiniteasyncsource/CS/InfiniteAsyncSourceSample/MainWindow.xaml.cs#L26
source.GetUniqueValues += (o, e) => {
if(e.PropertyName == "Priority") {
wpf-data-grid-bind-to-custom-service-with-restrictions/VB/MainWindow.xaml.vb#L20
AddHandler source.FetchRows, Sub(o, e) e.Result = FetchRowsAsync(e)
AddHandler source.GetUniqueValues, Sub(o, e) e.Result = GetUniqueValuesAsync(e.PropertyName)
Me.grid.ItemsSource = source
wpf-data-grid-use-virtual-sources-to-bind-to-in-memory-data/VB/MainWindow.xaml.vb#L22
AddHandler source.GetTotalSummaries, Sub(o, e) e.Result = GetTotalSummaries(e, getSourceTask)
AddHandler source.GetUniqueValues, Sub(o, e)
If Equals(e.PropertyName, "Priority") Then
See Also