How to: Filter an object's properties using the CustomPropertyDescriptors event

• Aug 01, 2019
• 2 minutes to read

This example shows how to display specific properties in a PropertyGridControl, while hiding other properties. Properties to be displayed are filtered via the CustomPropertyDescriptors event.At the root level the Dock, Size and Location properties are displayed. For the Size property, only the Height nested property is displayed.

Note

A complete sample project is available at https://github.com/DevExpress-Examples/how-to-filter-an-objects-properties-using-the-custompropertydescriptors-event-e2254

Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using DevExpress.XtraVerticalGrid.Events;

namespace PropertyFiltering {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
            this.propertyGridControl1.SelectedObject = this.propertyGridControl1;
            this.propertyGridControl1.GetRowByFieldName("Size").Expanded = true;
            this.propertyGridControl1.GetRowByFieldName("Location").Expanded = true;
        }

        void propertyGridControl1_CustomPropertyDescriptors(object sender, CustomPropertyDescriptorsEventArgs e) {
            // Provide properties to be displayed at the root level
            if(e.Context.PropertyDescriptor == null) {
                PropertyDescriptorCollection filteredCollection = new PropertyDescriptorCollection(null);
                AddIfPropertyExist(e.Properties, filteredCollection, "Dock");
                AddIfPropertyExist(e.Properties, filteredCollection, "Size");
                AddIfPropertyExist(e.Properties, filteredCollection, "Location");
                AddIfPropertyExist(e.Properties, filteredCollection, "NonexistentProperty");
                e.Properties = filteredCollection;
            }
            //Provide nested properties for the Size property
            if(e.Context.PropertyDescriptor != null && e.Context.PropertyDescriptor.Name == "Size") {
                PropertyDescriptorCollection filteredCollection = new PropertyDescriptorCollection(null);
                AddIfPropertyExist(e.Properties, filteredCollection, "Height");
                e.Properties = filteredCollection;
            }
        }
        void AddIfPropertyExist(PropertyDescriptorCollection sourceCollection, PropertyDescriptorCollection targetCollection, string name) {
            PropertyDescriptor foundPropertyDescriptor = sourceCollection[name];
            if(foundPropertyDescriptor == null)
                return;
            targetCollection.Add(foundPropertyDescriptor);
        }
    }
}

Form1.vb

Imports Microsoft.VisualBasic
Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Text
Imports System.Windows.Forms
Imports DevExpress.XtraVerticalGrid.Events

Namespace PropertyFiltering
    Partial Public Class Form1
        Inherits Form
        Public Sub New()
            InitializeComponent()
            Me.propertyGridControl1.SelectedObject = Me.propertyGridControl1
            Me.propertyGridControl1.GetRowByFieldName("Size").Expanded = True
            Me.propertyGridControl1.GetRowByFieldName("Location").Expanded = True
        End Sub

        Private Sub propertyGridControl1_CustomPropertyDescriptors(ByVal sender As Object, ByVal e As CustomPropertyDescriptorsEventArgs) Handles propertyGridControl1.CustomPropertyDescriptors
            ' Provide properties to be displayed at the root level
            If e.Context.PropertyDescriptor Is Nothing Then
                Dim filteredCollection As New PropertyDescriptorCollection(Nothing)
                AddIfPropertyExist(e.Properties, filteredCollection, "Dock")
                AddIfPropertyExist(e.Properties, filteredCollection, "Size")
                AddIfPropertyExist(e.Properties, filteredCollection, "Location")
                AddIfPropertyExist(e.Properties, filteredCollection, "NonexistentProperty")
                e.Properties = filteredCollection
            End If
            'Provide nested properties for the Size property
            If e.Context.PropertyDescriptor IsNot Nothing AndAlso e.Context.PropertyDescriptor.Name = "Size" Then
                Dim filteredCollection As New PropertyDescriptorCollection(Nothing)
                AddIfPropertyExist(e.Properties, filteredCollection, "Height")
                e.Properties = filteredCollection
            End If
        End Sub
        Private Sub AddIfPropertyExist(ByVal sourceCollection As PropertyDescriptorCollection, ByVal targetCollection As PropertyDescriptorCollection, ByVal name As String)
            Dim foundPropertyDescriptor As PropertyDescriptor = sourceCollection(name)
            If foundPropertyDescriptor Is Nothing Then
                Return
            End If
            targetCollection.Add(foundPropertyDescriptor)
        End Sub
    End Class
End Namespace