使用變更通知設計絕佳的資料來源 (Windows Forms .NET)
Windows Forms 資料繫結最重要的概念之一是變更通知。 若要確保您的資料來源和繫結控制項一律具有最新的資料，您必須新增資料繫結的變更通知。 具體來說，您想要確保繫結控制項會收到對其資料來源進行變更的通知。 資料來源會收到控制項繫結屬性變更的通知。
根據資料繫結的類型而定，有不同類型的變更通知：
簡單繫結，其中單一控制項屬性會繫結至物件的單一執行個體。
清單型繫結，可包含繫結至清單中項目屬性的單一控制項屬性，或繫結至物件清單的控制項屬性。
此外，如果您正在建立要用於資料繫結的 Windows Forms 控制項，則必須將 PropertyName 變更模式套用至控制項。 將模式套用至控制項會導致控制項繫結屬性的變更傳播至資料來源。
簡單繫結的變更通知
對於簡單繫結，當繫結屬性的值變更時，商務物件必須提供變更通知。 您可以公開商務物件中每個屬性的 PropertyNameChanged 事件，以提供變更通知。 它也需要以 BindingSource 或慣用的方法將商務物件繫結至控制項，讓商務物件實作 INotifyPropertyChanged 介面，並在屬性值變更時引發 PropertyChanged 事件。 當您使用實作 INotifyPropertyChanged 介面的物件時，不需要使用 BindingSource 將物件繫結至控制項。 但建議使用 BindingSource。
清單型繫結的變更通知
Windows Forms 相依於繫結清單，以將屬性變更與清單變更資訊提供給繫結控制項。 屬性變更是清單項目屬性值變更，而清單變更是刪除或新增至清單的項目。 因此，用於資料繫結的清單必須實作 IBindingList，以提供這兩種類型的變更通知。 BindingList<T> 是 IBindingList 的泛型實作，其設計目的是要與 Windows Forms 資料繫結搭配使用。 您可以建立包含實作 INotifyPropertyChanged 之商務物件類型的 BindingList，而清單會自動將 PropertyChanged 事件轉換為事件 ListChanged。 如果繫結清單不是 IBindingList，則您必須使用 BindingSource 元件將物件清單繫結至 Windows Forms 控制項。 BindingSource 元件會提供類似於 BindingList 元件的屬性對清單轉換。 如需詳細資訊，請參閱操作說明：使用 BindingSource 和 INotifyPropertyChanged 介面引發變更告知。
自訂控制項的變更通知
最後，從控制項端，您必須針對設計用來繫結至資料的每個屬性公開 PropertyName 變更事件。 然後，控制項屬性的變更會傳播至繫結的資料來源。 如需詳細資訊，請參閱套用 PropertyNameChanged 模式。
套用 PropertyNameChanged 模式
下列程式碼範例示範如何將 PropertyName 變更模式套用至自訂控制項。 當您實作與 Windows Forms 資料繫結引擎搭配使用的自訂控制項時，請套用模式。
// 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
實作 INotifyPropertyChanged 介面
下列程式碼範例示範如何實作 INotifyPropertyChanged 介面。 在 Windows Forms 資料繫結中使用的商務物件上實作介面。 實作之後，介面會與繫結的控制項傳達商務物件的屬性變更。
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
同步繫結
在 Windows Forms 中實作資料繫結期間，多個控制項會繫結至相同的資料來源。 在某些情況下，可能需要採取額外的步驟，以確保控制項的繫結屬性彼此和與資料來源保持同步。 在兩種情況下，這些步驟是必要的：
如果資料來源未實作 IBindingList，因此會產生 ItemChanged 類型的 ListChanged 事件。
如果資料來源實作 IEditableObject。
在先前的案例中，您可以使用 BindingSource 將資料來源 繫結至控制項。 在後者的情況下，您會使用 BindingSource 並處理 BindingComplete 事件，並在相關聯的 BindingManagerBase 上呼叫 EndCurrentEdit。
如需實作此概念的詳細資訊，請參閱 BindingComplete API 參考頁面。
