Como acionar notificações de alteração usando um BindingSource e a interface INotifyPropertyChanged

Artigo
10/18/2023

O BindingSource componente detecta automaticamente alterações em uma fonte de dados quando o tipo contido na fonte de dados implementa e gera PropertyChanged eventos quando um valor de INotifyPropertyChanged propriedade é alterado. Essa detecção de alterações é útil porque os controles vinculados à atualização automática à medida que os BindingSource valores da fonte de dados mudam.

Observação

Se sua fonte de dados for implementada e você estiver executando operações assíncronas INotifyPropertyChanged , não deverá fazer alterações na fonte de dados em um thread em segundo plano. Em vez disso, você deve ler os dados em um thread em segundo plano e mesclar os dados em uma lista no thread da interface do usuário.

Exemplo

O exemplo de código a INotifyPropertyChanged seguir demonstra uma implementação simples da interface. Ele também mostra como o automaticamente passa uma alteração de fonte de dados para um controle acoplado quando o BindingSource BindingSource é vinculado a uma lista do INotifyPropertyChanged tipo.

Se você usar o atributo CallerMemberName, chamadas para o método NotifyPropertyChanged não precisarão especificar o nome da propriedade como um argumento de cadeia de caracteres. Para obter mais informações, consulte Informações do chamador (C#) ou Informações do chamador (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();
                }
            }
        }
    }
}

Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Drawing
Imports System.Runtime.CompilerServices
Imports System.Windows.Forms

' 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 Class Form1
    Inherits System.Windows.Forms.Form
    ' This button causes the value of a list element to be changed.
    Private changeItemBtn As New Button()

    ' This DataGridView control displays the contents of the list.
    Private customersDataGridView As New DataGridView()

    ' This BindingSource binds the list to the DataGridView control.
    Private customersBindingSource As New BindingSource()

    Public Sub New()
        InitializeComponent()

        ' Set up the "Change Item" button.
        Me.changeItemBtn.Text = "Change Item"
        Me.changeItemBtn.Dock = DockStyle.Bottom
        AddHandler Me.changeItemBtn.Click, AddressOf changeItemBtn_Click
        Me.Controls.Add(Me.changeItemBtn)

        ' Set up the DataGridView.
        customersDataGridView.Dock = DockStyle.Top
        Me.Controls.Add(customersDataGridView)

        Me.Size = New Size(400, 200)
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles Me.Load

        ' Create and populate the list of DemoCustomer objects
        ' which will supply data to the DataGridView.
        Dim customerList As New BindingList(Of DemoCustomer)

        customerList.Add(DemoCustomer.CreateNewCustomer())
        customerList.Add(DemoCustomer.CreateNewCustomer())
        customerList.Add(DemoCustomer.CreateNewCustomer())

        ' Bind the list to the BindingSource.
        Me.customersBindingSource.DataSource = customerList

        ' Attach the BindingSource to the DataGridView.
        Me.customersDataGridView.DataSource = Me.customersBindingSource
    End Sub

    ' This event handler changes the value of the CompanyName
    ' property for the first item in the list.
    Private Sub changeItemBtn_Click(ByVal sender As Object, ByVal e As EventArgs)
        ' Get a reference to the list from the BindingSource.
        Dim customerList As BindingList(Of DemoCustomer) = _
            CType(customersBindingSource.DataSource, BindingList(Of 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"
    End Sub
End Class

' This class implements a simple customer type 
' that implements the IPropertyChange interface.
Public Class DemoCustomer
    Implements INotifyPropertyChanged

    ' These fields hold the values for the public properties.
    Private idValue As Guid = Guid.NewGuid()
    Private customerNameValue As String = String.Empty
    Private phoneNumberValue As String = String.Empty

    Public Event PropertyChanged As PropertyChangedEventHandler _
        Implements INotifyPropertyChanged.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 Sub NotifyPropertyChanged(<CallerMemberName()> Optional ByVal propertyName As String = Nothing)
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
    End Sub

    ' The constructor is private to enforce the factory pattern.
    Private Sub New()
        customerNameValue = "Customer"
        phoneNumberValue = "(312)555-0100"
    End Sub

    ' This is the public factory method.
    Public Shared Function CreateNewCustomer() As DemoCustomer
        Return New DemoCustomer()
    End Function

    ' This property represents an ID, suitable
    ' for use as a primary key in a database.
    Public ReadOnly Property ID() As Guid
        Get
            Return Me.idValue
        End Get
    End Property

    Public Property CustomerName() As String
        Get
            Return Me.customerNameValue
        End Get

        Set(ByVal value As String)
            If Not (value = customerNameValue) Then
                Me.customerNameValue = value
                NotifyPropertyChanged()
            End If
        End Set
    End Property

    Public Property PhoneNumber() As String
        Get
            Return Me.phoneNumberValue
        End Get

        Set(ByVal value As String)
            If Not (value = phoneNumberValue) Then
                Me.phoneNumberValue = value
                NotifyPropertyChanged()
            End If
        End Set
    End Property
End Class

Compilando o código

Este exemplo requer:

Referências aos assemblies System, System.Data, System.Drawing e System.Windows.Forms.

Partilhar via

Como acionar notificações de alteração usando um BindingSource e a interface INotifyPropertyChanged

Exemplo

Compilando o código

Confira também

Recursos adicionais