Mendesain sumber data hebat dengan pemberitahuan perubahan (Formulir Windows .NET)
Salah satu konsep terpenting dari pengikatan data Formulir Windows adalah pemberitahuan perubahan. Untuk memastikan bahwa sumber data dan kontrol terikat Anda selalu memiliki data terbaru, Anda harus menambahkan pemberitahuan perubahan untuk pengikatan data. Secara khusus, Anda ingin memastikan bahwa kontrol terikat diberitahu tentang perubahan yang dibuat pada sumber data mereka. Sumber data diberi tahu tentang perubahan yang dibuat pada properti terikat kontrol.
Ada berbagai jenis pemberitahuan perubahan, tergantung pada jenis pengikatan data:
Pengikatan sederhana, di mana satu properti kontrol terikat ke satu instans objek.
Pengikatan berbasis daftar, yang dapat menyertakan properti kontrol tunggal yang terikat ke properti item dalam daftar atau properti kontrol yang terikat ke daftar objek.
Selain itu, jika Anda membuat kontrol Formulir Windows yang ingin Anda gunakan untuk pengikatan data, Anda harus menerapkan pola PropertyNameChanged ke kontrol. Menerapkan pola ke kontrol menghasilkan perubahan pada properti terikat kontrol disebarluaskan ke sumber data.
Mengubah pemberitahuan untuk pengikatan sederhana
Untuk pengikatan sederhana, objek bisnis harus memberikan pemberitahuan perubahan saat nilai properti terikat berubah. Anda dapat memberikan pemberitahuan perubahan dengan mengekspos peristiwa PropertyNameChanged untuk setiap properti objek bisnis Anda. Ini juga memerlukan pengikatan objek bisnis untuk mengontrol dengan BindingSource atau metode pilihan di mana objek bisnis Anda mengimplementasikan INotifyPropertyChanged antarmuka dan meningkatkan PropertyChanged peristiwa ketika nilai properti berubah. Saat Anda menggunakan objek yang mengimplementasikan INotifyPropertyChanged antarmuka, Anda tidak perlu menggunakan BindingSource untuk mengikat objek ke kontrol. Tetapi menggunakan disarankan BindingSource .
Mengubah pemberitahuan untuk pengikatan berbasis daftar
Formulir Windows bergantung pada daftar terikat untuk memberikan informasi perubahan properti dan perubahan daftar ke kontrol terikat. Perubahan properti adalah perubahan nilai properti item daftar dan perubahan daftar adalah item yang dihapus atau ditambahkan ke daftar. Oleh karena itu, daftar yang digunakan untuk pengikatan data harus menerapkan IBindingList, yang menyediakan kedua jenis pemberitahuan perubahan. BindingList<T> adalah implementasi generik dan IBindingList dirancang untuk digunakan dengan pengikatan data Formulir Windows. Anda dapat membuat yang BindingList berisi jenis objek bisnis yang diterapkan INotifyPropertyChanged dan daftar akan secara otomatis mengonversi peristiwa menjadi PropertyChangedListChanged peristiwa. Jika daftar terikat bukan , IBindingListAnda harus mengikat daftar objek ke kontrol Formulir Windows dengan menggunakan BindingSource komponen . Komponen BindingSource akan menyediakan konversi properti-ke-daftar yang BindingListmirip dengan dari . Untuk informasi selengkapnya, lihat Cara: Menaikkan Pemberitahuan Perubahan Menggunakan BindingSource dan Antarmuka INotifyPropertyChanged.
Mengubah pemberitahuan untuk kontrol kustom
Terakhir, dari sisi kontrol, Anda harus mengekspos peristiwa PropertyNameChanged untuk setiap properti yang dirancang untuk terikat ke data. Perubahan pada properti kontrol kemudian disebarluaskan ke sumber data terikat. Untuk informasi selengkapnya, lihat Menerapkan pola PropertyNameChanged.
Menerapkan pola PropertyNameChanged
Contoh kode berikut menunjukkan cara menerapkan pola PropertyNameChanged ke kontrol kustom. Terapkan pola saat Anda menerapkan kontrol kustom yang digunakan dengan mesin pengikatan data Formulir Windows.
// This class implements a simple user control
// that demonstrates how to apply the propertyNameChanged pattern.
[ComplexBindingProperties("DataSource", "DataMember")]
public class CustomerControl : UserControl
{
private DataGridView dataGridView1;
private Label label1;
private DateTime lastUpdate = DateTime.Now;
public EventHandler DataSourceChanged;
public object DataSource
{
get
{
return this.dataGridView1.DataSource;
}
set
{
if (DataSource != value)
{
this.dataGridView1.DataSource = value;
OnDataSourceChanged();
}
}
}
public string DataMember
{
get { return this.dataGridView1.DataMember; }
set { this.dataGridView1.DataMember = value; }
}
private void OnDataSourceChanged()
{
if (DataSourceChanged != null)
{
DataSourceChanged(this, new EventArgs());
}
}
public CustomerControl()
{
this.dataGridView1 = new System.Windows.Forms.DataGridView();
this.label1 = new System.Windows.Forms.Label();
this.dataGridView1.ColumnHeadersHeightSizeMode =
System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
this.dataGridView1.ImeMode = System.Windows.Forms.ImeMode.Disable;
this.dataGridView1.Location = new System.Drawing.Point(100, 100);
this.dataGridView1.Size = new System.Drawing.Size(500,500);
this.dataGridView1.TabIndex = 1;
this.label1.AutoSize = true;
this.label1.Location = new System.Drawing.Point(50, 50);
this.label1.Name = "label1";
this.label1.Size = new System.Drawing.Size(76, 13);
this.label1.TabIndex = 2;
this.label1.Text = "Customer List:";
this.Controls.Add(this.label1);
this.Controls.Add(this.dataGridView1);
this.Size = new System.Drawing.Size(450, 250);
}
}
' This class implements a simple user control
' that demonstrates how to apply the propertyNameChanged pattern.
<ComplexBindingProperties("DataSource", "DataMember")>
Public Class CustomerControl
Inherits UserControl
Private dataGridView1 As DataGridView
Private label1 As Label
Private lastUpdate As DateTime = DateTime.Now
Public DataSourceChanged As EventHandler
Public Property DataSource() As Object
Get
Return Me.dataGridView1.DataSource
End Get
Set
If DataSource IsNot Value Then
Me.dataGridView1.DataSource = Value
OnDataSourceChanged()
End If
End Set
End Property
Public Property DataMember() As String
Get
Return Me.dataGridView1.DataMember
End Get
Set
Me.dataGridView1.DataMember = Value
End Set
End Property
Private Sub OnDataSourceChanged()
If (DataSourceChanged IsNot Nothing) Then
DataSourceChanged(Me, New EventArgs())
End If
End Sub
Public Sub New()
Me.dataGridView1 = New System.Windows.Forms.DataGridView()
Me.label1 = New System.Windows.Forms.Label()
Me.dataGridView1.ColumnHeadersHeightSizeMode =
System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize
Me.dataGridView1.ImeMode = System.Windows.Forms.ImeMode.Disable
Me.dataGridView1.Location = New System.Drawing.Point(19, 55)
Me.dataGridView1.Size = New System.Drawing.Size(550, 150)
Me.dataGridView1.TabIndex = 1
Me.label1.AutoSize = True
Me.label1.Location = New System.Drawing.Point(19, 23)
Me.label1.Name = "label1"
Me.label1.Size = New System.Drawing.Size(76, 13)
Me.label1.TabIndex = 2
Me.label1.Text = "Customer List:"
Me.Controls.Add(Me.label1)
Me.Controls.Add(Me.dataGridView1)
Me.Size = New System.Drawing.Size(650, 300)
End Sub
End Class
Menerapkan antarmuka INotifyPropertyChanged
Contoh kode berikut menunjukkan cara mengimplementasikan INotifyPropertyChanged antarmuka. Terapkan antarmuka pada objek bisnis yang digunakan dalam pengikatan data Formulir Windows. Saat diimplementasikan, antarmuka berkomunikasi ke kontrol terikat perubahan properti pada objek bisnis.
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 binding_control_example
{
// This form demonstrates using a BindingSource to bind
// a list to a DataGridView control. The list does not
// raise change notifications. However the DemoCustomer1 type
// in the list does.
public partial class Form3 : 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 Form3()
{
InitializeComponent();
// Set up the "Change Item" button.
this.changeItemBtn.Text = "Change Item";
this.changeItemBtn.Dock = DockStyle.Bottom;
this.changeItemBtn.Height = 100;
//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 Form3_Load(object sender, EventArgs e)
{
this.Top = 100;
this.Left = 100;
this.Height = 600;
this.Width = 1000;
// Create and populate the list of DemoCustomer objects
// which will supply data to the DataGridView.
BindingList<DemoCustomer1> customerList = new ();
customerList.Add(DemoCustomer1.CreateNewCustomer());
customerList.Add(DemoCustomer1.CreateNewCustomer());
customerList.Add(DemoCustomer1.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<DemoCustomer1>? customerList =
this.customersBindingSource.DataSource as BindingList<DemoCustomer1>;
// 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 DemoCustomer1 : 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 DemoCustomer1()
{
customerNameValue = "Customer";
phoneNumberValue = "(312)555-0100";
}
// This is the public factory method.
public static DemoCustomer1 CreateNewCustomer()
{
return new DemoCustomer1();
}
// 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 DemoCustomer1 type
' in the list does.
Public Class Form3
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
Me.changeItemBtn.Size = New System.Drawing.Size(100, 100)
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 Form3_Load(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles Me.Load
Me.Top = 100
Me.Left = 100
Me.Height = 600
Me.Width = 1000
' Create and populate the list of DemoCustomer1 objects
' which will supply data to the DataGridView.
Dim customerList As New BindingList(Of DemoCustomer1)
customerList.Add(DemoCustomer1.CreateNewCustomer())
customerList.Add(DemoCustomer1.CreateNewCustomer())
customerList.Add(DemoCustomer1.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 DemoCustomer1) =
CType(customersBindingSource.DataSource, BindingList(Of DemoCustomer1))
' 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 DemoCustomer1
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 DemoCustomer1
Return New DemoCustomer1()
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
Menyinkronkan pengikatan
Selama implementasi pengikatan data di Formulir Windows, beberapa kontrol terikat ke sumber data yang sama. Dalam beberapa kasus, mungkin perlu mengambil langkah tambahan untuk memastikan bahwa properti terikat kontrol tetap disinkronkan satu sama lain dan sumber data. Langkah-langkah ini diperlukan dalam dua situasi:
Jika sumber data tidak mengimplementasikan IBindingList, dan karena itu menghasilkan ListChanged peristiwa jenis ItemChanged.
Jika sumber data mengimplementasikan IEditableObject.
Dalam kasus sebelumnya, Anda dapat menggunakan BindingSource untuk mengikat sumber data ke kontrol. Dalam kasus terakhir, Anda menggunakan BindingSource dan menangani BindingComplete peristiwa dan memanggil EndCurrentEdit pada BindingManagerBase.
Untuk informasi selengkapnya tentang menerapkan konsep ini, lihat halaman referensi API BindingComplete.
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