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How to: Implement the INotifyPropertyChanged Interface

The following code example demonstrates how to implement the INotifyPropertyChanged interface. Implement this interface on business objects that are used in Windows Forms data binding. When implemented, the interface communicates to a bound control the property changes on a business object.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Runtime.CompilerServices;
using System.Windows.Forms;

// Change the namespace to the project name. 
namespace TestNotifyPropertyChangedCS
{
    // This form demonstrates using a BindingSource to bind 
    // a list to a DataGridView control. The list does not 
    // raise change notifications. However the DemoCustomer type  
    // in the list does. 
    public partial class Form1 : Form
    {
        // This button causes the value of a list element to be changed. 
        private Button changeItemBtn = new Button();

        // This DataGridView control displays the contents of the list. 
        private DataGridView customersDataGridView = new DataGridView();

        // This BindingSource binds the list to the DataGridView control. 
        private BindingSource customersBindingSource = new BindingSource();

        public Form1()
        {
            InitializeComponent();

            // Set up the "Change Item" button.
            this.changeItemBtn.Text = "Change Item";
            this.changeItemBtn.Dock = DockStyle.Bottom;
            this.changeItemBtn.Click +=
                new EventHandler(changeItemBtn_Click);
            this.Controls.Add(this.changeItemBtn);

            // Set up the DataGridView.
            customersDataGridView.Dock = DockStyle.Top;
            this.Controls.Add(customersDataGridView);

            this.Size = new Size(400, 200);
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // Create and populate the list of DemoCustomer objects 
            // which will supply data to the DataGridView.
            BindingList<DemoCustomer> customerList = new BindingList<DemoCustomer>();
            customerList.Add(DemoCustomer.CreateNewCustomer());
            customerList.Add(DemoCustomer.CreateNewCustomer());
            customerList.Add(DemoCustomer.CreateNewCustomer());

            // Bind the list to the BindingSource. 
            this.customersBindingSource.DataSource = customerList;

            // Attach the BindingSource to the DataGridView. 
            this.customersDataGridView.DataSource =
                this.customersBindingSource;

        }

        // Change the value of the CompanyName property for the first  
        // item in the list when the "Change Item" button is clicked.
        void changeItemBtn_Click(object sender, EventArgs e)
        {
            // Get a reference to the list from the BindingSource.
            BindingList<DemoCustomer> customerList =
                this.customersBindingSource.DataSource as BindingList<DemoCustomer>;

            // Change the value of the CompanyName property for the  
            // first item in the list.
            customerList[0].CustomerName = "Tailspin Toys";
            customerList[0].PhoneNumber = "(708)555-0150";
        }

    }

    // This is a simple customer class that  
    // implements the IPropertyChange interface. 
    public class DemoCustomer : INotifyPropertyChanged
    {
        // These fields hold the values for the public properties. 
        private Guid idValue = Guid.NewGuid();
        private string customerNameValue = String.Empty;
        private string phoneNumberValue = String.Empty;

        public event PropertyChangedEventHandler PropertyChanged;

        // This method is called by the Set accessor of each property. 
        // The CallerMemberName attribute that is applied to the optional propertyName 
        // parameter causes the property name of the caller to be substituted as an argument. 
        private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        // The constructor is private to enforce the factory pattern. 
        private DemoCustomer()
        {
            customerNameValue = "Customer";
            phoneNumberValue = "(312)555-0100";
        }

        // This is the public factory method. 
        public static DemoCustomer CreateNewCustomer()
        {
            return new DemoCustomer();
        }

        // This property represents an ID, suitable 
        // for use as a primary key in a database. 
        public Guid ID
        {
            get
            {
                return this.idValue;
            }
        }

        public string CustomerName
        {
            get
            {
                return this.customerNameValue;
            }

            set
            {
                if (value != this.customerNameValue)
                {
                    this.customerNameValue = value;
                    NotifyPropertyChanged();
                }
            }
        }

        public string PhoneNumber
        {
            get
            {
                return this.phoneNumberValue;
            }

            set
            {
                if (value != this.phoneNumberValue)
                {
                    this.phoneNumberValue = value;
                    NotifyPropertyChanged();
                }
            }
        }
    }
}
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