Como: Gerar notificações de alterações usando a interface INotifyPropertyChanged e uma BindingSource

Artigo
08/25/2010

The BindingSource componente detectará automaticamente as alterações em uma fonte de dados quando o tipo contido na implementa de fonte de dados do INotifyPropertyChanged interface e gera PropertyChanged eventos quando um valor da propriedade é alterado. Isso é útil porque controles vinculados a BindingSource em seguida, atualizará automaticamente sistema autônomo sendo a alterar de valores de fonte de dados.

Observação:
Se seus dados de fonte implementa INotifyPropertyChanged e você estiver executando operações assíncrono, você não deve fazer alterações na fonte de dados em um plano de fundo thread. Em vez disso, você deve ler os dados em um plano de fundo threads e mesclagem os dados em uma lista no thread da interface do usuário.

Exemplo

O exemplo de código a seguir demonstra uma implementação simples do INotifyPropertyChanged interface. Ele também mostra como a BindingSource passe uma alterar de fonte de dados automaticamente para um limite de controle quando o BindingSource está vinculado a uma lista da INotifyPropertyChanged Digite.

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Data.Common
Imports System.Diagnostics
Imports System.Drawing
Imports System.Data.SqlClient
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 is the DataGridView control that displays the contents 
    ' of the list.
    Private customersDataGridView As New DataGridView()

    ' This is the BindingSource used to bind the list to the 
    ' DataGridView control.
    Private customersBindingSource As New BindingSource()

    Public Sub New() 
        ' 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(800, 200)
        AddHandler Me.Load, AddressOf Form1_Load

    End Sub 'New

    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 List(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 'Form1_Load

    ' 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 List(Of DemoCustomer) = _
            CType(customersBindingSource.DataSource, List(Of DemoCustomer))

        ' Change the value of the CompanyName property for the 
        ' first item in the list.
        customerList(0).CompanyName = "Tailspin Toys"

    End Sub



    <STAThread()>  _
    Shared Sub Main() 
        Application.EnableVisualStyles()
        Application.Run(New Form1())

    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 customerName As String = String.Empty
    Private companyNameValue As String = String.Empty
    Private phoneNumberValue As String = String.Empty

    Public Event PropertyChanged As PropertyChangedEventHandler _
        Implements INotifyPropertyChanged.PropertyChanged


    Private Sub NotifyPropertyChanged(ByVal info As String) 
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(info))
    End Sub

    ' The constructor is private to enforce the factory pattern.
    Private Sub New() 
        customerName = "no data"
        companyNameValue = "no data"
        phoneNumberValue = "no data"

    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 CompanyName() As String 
        Get
            Return Me.companyNameValue
        End Get

        Set(ByVal value As String)
            If Not (value = companyNameValue) Then
                Me.companyNameValue = value
                NotifyPropertyChanged("CompanyName")
            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("PhoneNumber")
            End If

        End Set
    End Property
End Class

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.Common;
using System.Diagnostics;
using System.Drawing;
using System.Data.SqlClient;
using 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 : System.Windows.Forms.Form
{
    // This button causes the value of a list element to be changed.
    private Button changeItemBtn = new Button();

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

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

    public Form1()
    {
        // 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(800, 200);
        this.Load += new EventHandler(Form1_Load);
    }

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

    // This event handler changes the value of the CompanyName
    // property for the first item in the list.
    void changeItemBtn_Click(object sender, EventArgs e)
    {
        // Get a reference to the list from the BindingSource.
        List<DemoCustomer> customerList =
            this.customersBindingSource.DataSource as List<DemoCustomer>;

        // Change the value of the CompanyName property for the 
        // first item in the list.
        customerList[0].CompanyName = "Tailspin Toys";

    }

    

    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.Run(new Form1());
    }
}

// This class implements a simple customer type 
// 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 customerName = String.Empty;
    private string companyNameValue = String.Empty;
    private string phoneNumberValue = String.Empty;

    public event PropertyChangedEventHandler PropertyChanged;
    
    private void NotifyPropertyChanged(String info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    // The constructor is private to enforce the factory pattern.
    private DemoCustomer()
    {
        customerName = "no data";
        companyNameValue = "no data";
        phoneNumberValue = "no data";
    }

    // 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 CompanyName
    {
        get
        {
            return this.companyNameValue;
        }

        set
        {
            if (value != this.companyNameValue)
            {
                this.companyNameValue = value;
                NotifyPropertyChanged("CompanyName");
            }
        }
    }

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

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

Compilando o código

Este exemplo requer:

Referências aos assemblies do sistema, System.dados, System.desenho e System.Windows.Forms.

Para obter informações sobre como criar este exemplo a partir da linha de comando para Visual Basic ou Visual C#, consulte Criando a partir da linha de comando (Visual Basic) ou Linha de comando criando com csc.exe.Você também pode construir este exemplo no Visual Studio colando o código em um novo projeto.

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Como: Gerar notificações de alterações usando a interface INotifyPropertyChanged e uma BindingSource

Exemplo

Compilando o código

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