How to: Raise Change Notifications Using a BindingSource and the INotifyPropertyChanged Interface

How to: Raise Change Notifications Using a BindingSource and the INotifyPropertyChanged Interface

 

The BindingSource component will automatically detect changes in a data source when the type contained in the data source implements the INotifyPropertyChanged interface and raises PropertyChanged events when a property value is changed. This is useful because controls bound to the BindingSource will then automatically update as the data source values change.

System_CAPS_noteNote

If your data source implements INotifyPropertyChanged and you are performing asynchronous operations, you should not make changes to the data source on a background thread. Instead, you should read the data on a background thread and merge the data into a list on the UI thread.

Example

The following code example demonstrates a simple implementation of the INotifyPropertyChanged interface. It also shows how the BindingSource automatically passes a data source change to a bound control when the BindingSource is bound to a list of the INotifyPropertyChanged type.

If you use the CallerMemberName attribute, calls to the NotifyPropertyChanged method don't have to specify the property name as a string argument. For more information, see Caller Information (C# and Visual Basic).

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();
                }
            }
        }
    }
}

Compiling the Code

This example requires:

  • References to the System, System.Data, System.Drawing and System.Windows.Forms assemblies.

For information about building this example from the command line for Visual Basic or Visual C#, see Building from the Command Line (Visual Basic) or Command-line Building With csc.exe. You can also build this example in Visual Studio by pasting the code into a new project. Also see HYPERLINK "http://msdn.microsoft.com/library/Bb129228(v=vs.110)" How to: Compile and Run a Complete Windows Forms Code Example Using Visual Studio.

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