FilterEditorControl.QueryOperators Event

Allows you to customize the operator list.

Namespace: DevExpress.Xpf.Core.FilteringUI

Assembly: DevExpress.Xpf.Grid.v23.2.dll

NuGet Package: DevExpress.Wpf.Grid.Core

Declaration

C#

public event EventHandler<FilterEditorQueryOperatorsEventArgs> QueryOperators

VB.NET

Public Event QueryOperators As EventHandler(Of FilterEditorQueryOperatorsEventArgs)

Event Data

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

Property	Description
DefaultOperator	Gets or sets an operator that is selected when users create a new filter condition. Inherited from QueryOperatorsEventArgsBase<T>.
FieldName	Gets a name of the field for which operators are queried. Inherited from QueryOperatorsEventArgsBase<T>.
Filter	Gets the current filter criteria specified in the FilterEditorControl.
Operators	Gets or sets the operators displayed in the operator list.

Remarks

Run Demo: Filter Editor - Customize the Operator List

The Filter Editor shows a list of operators the selected field accepts. Use the QueryOperators event to customize the operator list.

The code sample below removes all operators except Equal and Not Equal:

Xaml

<dxg:TableView x:Name="view">
    <dxg:TableView.FilterEditorTemplate>
        <DataTemplate>
            <dxfui:FilterEditorControl QueryOperators="OnQueryOperators" />
        </DataTemplate>
    </dxg:TableView.FilterEditorTemplate>
</dxg:TableView> 

C#

void OnQueryOperators(object sender, FilterEditorQueryOperatorsEventArgs e) {
    if(e.FieldName == "OrderDate") {
        e.Operators.Clear();
        e.Operators.Add(new FilterEditorOperatorItem(FilterEditorOperatorType.Equal));
        e.Operators.Add(new FilterEditorOperatorItem(FilterEditorOperatorType.NotEqual));
    }
} 

VB.NET

Private Sub OnQueryOperators(ByVal sender As Object, ByVal e As FilterEditorQueryOperatorsEventArgs)
    If e.FieldName = "OrderDate" Then
        e.Operators.Clear()
        e.Operators.Add(New FilterEditorOperatorItem(FilterEditorOperatorType.Equal))
        e.Operators.Add(New FilterEditorOperatorItem(FilterEditorOperatorType.NotEqual))
    End If
End Sub 

Custom Operators

You can use the QueryOperators event to add custom operators. The code sample below adds the Last Years operator:

1. Create a custom function. Do one of the following:

   • Use the CustomFunctionFactory.Create method.

     The CustomFunctionFactory is an extension of the DevExpress.Xpf.Grid.v23.2.Extensions.dll library. Refer to C:\Program Files\DevExpress 23.2\Components\Sources\XPF\DevExpress.Xpf.Grid\DevExpress.Xpf.Grid.Extensions\ for information on how extension methods work.

     The CustomFunctionFactory.Create method allows you to create a custom function with a maximum of 4 operands.

   • Implement the ICustomFunctionOperator interface. Refer to the Implementing Custom Functions topic for more information.

   C#

   const string CustomFunctionName = "LastYears";
   var currentYear = DateTime.Now.Year;
   
   ICustomFunctionOperatorBrowsable customFunction = CustomFunctionFactory.Create(CustomFunctionName, 
       (DateTime date, int threshold) => {
           return currentYear >= date.Year && currentYear - date.Year <= threshold;
       }
   );
   

   VB.NET

   Const CustomFunctionName As String = "LastYears"
   Private currentYear = DateTime.Now.Year
   
   Dim customFunction As ICustomFunctionOperatorBrowsable = CustomFunctionFactory.Create(CustomFunctionName, 
       Function(ByVal date As DateTime, ByVal threshold As Integer) currentYear >= date.Year AndAlso currentYear - date.Year <= threshold)
   

2. Call the CriteriaOperator.RegisterCustomFunction method to register the custom function.

   C#

   CriteriaOperator.RegisterCustomFunction(customFunction);
   

   VB.NET

   CriteriaOperator.RegisterCustomFunction(customFunction)
   

3. Create the FilterEditorOperatorItem and add it to the FilterEditorQueryOperatorsEventArgs.Operators collection. Specify the operator item’s edit settings to define its operands:

   C#

   void OnQueryOperators(object sender, FilterEditorQueryOperatorsEventArgs e) {
       if(e.FieldName == "OrderDate") {
           // ...
   
           var customFunctionEditSettings = new BaseEditSettings[] { 
               new TextEditSettings { MaskType = MaskType.Numeric, Mask = "D", MaskUseAsDisplayFormat = true } 
           };
           e.Operators.Add(new FilterEditorOperatorItem(CustomFunctionName, customFunctionEditSettings) { Caption = "Last Years" });
       }
   } 
   

   VB.NET

   Private Sub OnQueryOperators(ByVal sender As Object, ByVal e As FilterEditorQueryOperatorsEventArgs)
       If e.FieldName = "OrderDate" Then
           ' ...
   
           Dim customFunctionEditSettings = New BaseEditSettings() {New TextEditSettings With {
               .MaskType = MaskType.Numeric,
               .Mask = "D",
               .MaskUseAsDisplayFormat = True
           }}
           e.Operators.Add(New FilterEditorOperatorItem(CustomFunctionName, customFunctionEditSettings) With {
               .Caption = "Last Years"
           })
       End If
   End Sub