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Windows Forms 的Binding 类介绍

原创 Linux操作系统 作者:iDotNetSpace 时间:2008-01-22 17:38:02 0 删除 编辑

代表某对象属性值和某控件属性值之间的简单绑定。

命名空间:System.Windows.Forms
程序集:System.Windows.Forms(在 system.windows.forms.dll 中)

Visual Basic(声明)
Public Class Binding
Visual Basic(用法)
Dim instance As Binding
C#
public class Binding
C++
public ref class Binding
J#
public class Binding
JScript
public class Binding

使用 Binding 类来创建和维护某控件的属性与某对象的属性或对象列表中当前对象的属性之间的简单绑定。

作为第一种情况的示例,您可以将 TextBox 控件的 Text 属性绑定到 Customer 对象的 FirstName 属性。作为第二种情况的示例,您可以将 TextBox 控件的 Text 属性绑定到包含客户的 DataTableFirstName 属性。

Binding 类还使您可以格式化值以通过 Format 事件显示,以及通过 Parse 事件检索格式化的值。

当使用 Binding 构造函数构造 Binding 实例时,必须指定三项内容:

  • 要绑定到的控件属性的名称。

  • 数据源。

  • 数据源中解析为列表或属性的导航路径。导航路径还用于创建对象的 BindingMemberInfo 属性。

首先,您必须指定要将数据绑定到其上的控件属性的名称。例如,若要在 TextBox 控件中显示数据,请指定 Text 属性。

其次,可以指定下表中的任意一个类的实例作为数据源。

说明

C# 示例

实现 IBindingListITypedList 的任何类。包括:DataSetDataTableDataViewDataViewManager

DataSet ds = new DataSet("myDataSet");

实现 IList 以创建对象索引集合的任意类。必须在创建 Binding 之前创建和填充该集合。列表中的所有对象必须为同一类型;否则将引发异常。

ArrayList ar1 = new ArrayList;

Customer1 cust1 = new Customer("Louis");

ar1.Add(cust1);

强类型对象的强类型 IList

Customer [] custList = new Customer[3];

第三,必须指定导航路径,它可以为空字符串 ("")、单个属性名称或句点分隔的名称层次结构。如果将导航路径设置为空字符串,将在基础数据源对象上调用 ToString 方法。

如果数据源为可以包含多个 DataColumn 对象的 DataTable,则必须使用导航路径解析为特定列。

Note注意

当数据源为 DataSetDataViewManagerDataTable 时,实际将绑定到 DataView。因此,绑定行实际为 DataRowView 对象。

当数据源设置为包含多个 DataTable 对象的对象(如 DataSetDataViewManager)时,需要句点分隔的导航路径。当绑定到其属性返回对其他对象的引用的对象(如具有返回其他类对象的属性的类)时,也可以使用句点分隔的导航路径。例如,以下导航路径均描述有效数据字段:

  • “Size.Height”

  • “Suppliers.CompanyName”

  • “Regions.regionsToCustomers.CustomerFirstName”

  • “Regions.regionsToCustomers.customersToOrders.ordersToDetails.Quantity”

路径的每个成员既可以返回解析为单个值(如一个整数)的属性,也可以返回值的列表(如字符串数组)。尽管路径中的每个成员都可以是列表或属性,但最终成员必须解析为属性。每个成员都建立在前一个成员上:“Size.Height”解析为当前 SizeHeight 属性;“Regions.regionsToCustomers.CustomerFirstName”解析为当前客户的名字,该客户是当前区域的客户之一。

DataRelation 通过将 DataSet 中的一个 DataTable 与第二个 DataTable 链接来返回值列表。如果 DataSet 包含 DataRelation 对象,则可以将数据成员指定为 TableName,其后为 RelationName,然后是 ColumnName。例如,如果名为“Suppliers”的 DataTable 包含名为“suppliers2products”的 DataRelation,那么数据成员可能为“Suppliers.suppliers2products.ProductName”。

数据源可以由一组相关类组成。例如,设想对太阳系进行编录的一组类。名为 System 的类包含一个名为 Stars 的属性,后者返回 Star 对象的集合。每个 Star 对象都具有 NameMass 属性,以及一个返回 Planet 对象的集合的 Planets 属性。在此系统中,每个行星还有 MassName 属性。此外,每个 Planet 对象还拥有用来返回 Moon 对象集合的 Moons 属性,而每个 Moon 对象则有 NameMass 属性。如果将 System 对象指定为数据源,则可以将下列任意项指定为数据成员:

  • “Stars.Name”

  • “Stars.Mass”

  • “Stars.Planets.Name”

  • “Stars.Planets.Mass”

  • “Stars.Planets.Moons.Name”

  • “Stars.Planets.Moons.Mass”

可简单绑定的控件以 ControlBindingsCollectionBinding 对象的集合为特色,您可通过控件的 DataBindings 属性访问该集合。通过调用 Add 方法,从而将控件的属性绑定到某个对象的属性(或绑定到列表中当前对象的某个属性),可向集合添加 Binding

您可简单绑定到从 System.Windows.Forms.Control 类派生的任何对象,例如下列 Windows 控件:

Note注意

只有 ComboBoxCheckedListBoxListBox 控件的 SelectedValue 属性是简单绑定的。

BindingManagerBase 类是管理特定数据源和数据成员的所有 Binding 对象的抽象类。从 BindingManagerBase 派生的类是 CurrencyManager 类和 PropertyManager 类。如何管理 Binding 取决于 Binding 是列表绑定还是属性绑定。例如,如果是列表绑定,则可以使用 BindingManagerBase 指定列表中的 Position;因此 Position 确定了列表的所有项中的哪一项实际绑定到控件。若要返回适当的 BindingManagerBase,请使用 BindingContext

若要向绑定到同一 DataSource 的一组控件添加新行,请使用 BindingManagerBase 类的 AddNew 方法。使用 BindingContext 类的 Item 属性返回适当的 CurrencyManager。若要避免添加新行,请使用 CancelCurrentEdit 方法。

下面的代码示例创建一个带有若干控件的 Windows 窗体,这些控件演示简单数据绑定。示例创建一个 DataSet,它带有两个表(名为 CustomersOrders)以及名为 custToOrdersDataRelation。将四个控件(一个 DateTimePicker 控件和三个 TextBox 控件)的数据绑定到表中的列。对于每个控件,示例通过 DataBindings 属性创建一个 Binding 并将其添加到控件。示例通过窗体的 BindingContext 为每个表返回一个 BindingManagerBase。可使用四个 Button 控件来增加或减小 BindingManagerBase 对象上的 Position 属性。

Visual Basic
Imports System
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Globalization
Imports System.Windows.Forms

Public Class Form1
   Inherits Form. Private components As Container
   Private button1 As Button
   Private button2 As Button
   Private button3 As Button
   Private button4 As Button
   Private text1 As TextBox
   Private text2 As TextBox
   Private text3 As TextBox

   Private bmCustomers As BindingManagerBase
   Private bmOrders As BindingManagerBase
   Private ds As DataSet
   Private DateTimePicker1 As DateTimePicker
   
   Public Sub New
      ' Required for Windows Form. Designer support.
      InitializeComponent
      ' Call SetUp to bind the controls.
      SetUp
   End Sub

   Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
      If disposing Then
         If Not (components Is Nothing) Then
            components.Dispose()
         End If
      End If
      MyBase.Dispose(disposing)
    End Sub


   Private Sub InitializeComponent
      ' Create the form. and its controls.
      With Me
         .components = New Container
         .button1 = New Button
         .button2 = New Button
         .button3 = New Button
         .button4 = New Button
         .text1 = New TextBox
         .text2 = New TextBox
         .text3 = New TextBox

         .DateTimePicker1 = New DateTimePicker
         
         .Text = "Binding Sample"
         .ClientSize = New Size(450, 200)

         With .button1
            .Location = New Point(24, 16)
            .Size = New Size(64, 24)
            .Text = "<"
            AddHandler button1.click, AddressOf button1_Click
         End With
         
         
         With .button2
            .Location = New Point(90, 16)
            .Size = New Size(64, 24)
            .Text = ">"
            AddHandler button2.click, AddressOf button2_Click
         End With
         
         With .button3
            .Location = New Point(90, 100)
            .Size = New Size(64, 24)
            .Text = ">"
            AddHandler button3.click, AddressOf button3_Click
         End With

         With .button4
            .Location = New Point(150, 100)
            .Size = New Size(64, 24)
            .Text = ">"
            AddHandler button4.click, AddressOf button4_Click
         End With

         With .text1
            .Location = New Point(24, 50)
            .Size = New Size(150, 24)
         End With

         With .text2
            .Location = New Point(190, 50)
            .Size = New Size(150, 24)
         End With

         With .text3
            .Location = New Point(290, 150)
            .Size = New Size(150, 24)
         End With

            With .DateTimePicker1
               .Location = New Point(90, 150)
               .Size = New Size(200, 800)
            End With

            With .Controls
            .Add(button1)
            .Add(button2)
            .Add(button3)
            .Add(button4)
            .Add(text1)
            .Add(text2)
            .Add(text3)
            .Add(DateTimePicker1)
            End With
      End With
   End Sub
      
   Public Shared Sub Main
      Application.Run(new Form1)
   End Sub

   Private Sub SetUp
      ' Create a DataSet with two tables and one relation.
      MakeDataSet
      BindControls
   End Sub

   Private Sub BindControls
      ' Create two Binding objects for the first two TextBox
      ' controls. The data-bound property for both controls
      ' is the Text property.  The data source is a DataSet
      ' (ds). The data member is the 
      ' TableName.ColumnName" string.

      text1.DataBindings.Add(New _
         Binding("Text", ds, "customers.custName"))
      text2.DataBindings.Add(New _
         Binding("Text", ds, "customers.custID"))
      ' Bind the DateTimePicker control by adding a new Binding.
      ' The data member of the DateTimePicker is a
      ' TableName.RelationName.ColumnName string
      DateTimePicker1.DataBindings.Add(New _
         Binding("Value", ds, "customers.CustToOrders.OrderDate"))
      ' Add event delegates for the Parse and Format events to a
      ' new Binding object, and add the object to the third
      ' TextBox control's BindingsCollection. The delegates
      ' must be added before adding the Binding to the
      ' collection; otherwise, no formatting occurs until
      ' the Current object of the BindingManagerBase for
      ' the data source changes.
      Dim b As Binding = New _
         Binding("Text", ds, "customers.custToOrders.OrderAmount")
      AddHandler b.Parse, AddressOf CurrencyStringToDecimal
      AddHandler b.Format, AddressOf DecimalToCurrencyString
      text3.DataBindings.Add(b)
      
         ' Get the BindingManagerBase for the Customers table.
         bmCustomers = Me.BindingContext(ds, "Customers")

         ' Get the BindingManagerBase for the Orders table using the
         ' RelationName.
         bmOrders = Me.BindingContext(ds, "customers.CustToOrders")
   End Sub

   Private Sub DecimalToCurrencyString(sender As Object, cevent As ConvertEventArgs)
      ' This method is the Format event handler. Whenever the 
      ' control displays a new value, the value is converted from 
      ' its native Decimal type to a string. The ToString method 
      ' then formats the value as a Currency, by using the 
      ' formatting character "c".

      ' The application can only convert to string type. 
   
      If Not cevent.DesiredType Is GetType(String) Then
         Exit Sub
      End If 
   
      cevent.Value = CType(cevent.Value, decimal).ToString("c")
   End Sub

   Private Sub CurrencyStringToDecimal(sender As Object, cevent As ConvertEventArgs)
      ' This method is the Parse event handler. The Parse event 
      ' occurs whenever the displayed value changes. The static 
      ' ToDecimal method of the Convert class converts the 
      ' value back to its native Decimal type.

      ' Can only convert to decimal type.
      If Not cevent.DesiredType Is GetType(decimal) Then
         Exit Sub
      End If

      cevent.Value = Decimal.Parse(cevent.Value.ToString, _
      NumberStyles.Currency, nothing)
      
      ' To see that no precision is lost, print the unformatted 
      ' value. For example, changing a value to "10.0001" 
      ' causes the control to display "10.00", but the 
      ' unformatted value remains "10.0001".
      Console.WriteLine(cevent.Value)
   End Sub

   Private Sub button1_Click(sender As Object, e As System.EventArgs)
      ' Go to the previous item in the Customer list.
      bmCustomers.Position -= 1
   End Sub

   Private Sub button2_Click(sender As Object, e As System.EventArgs)
      ' Go to the next item in the Customer list.
      bmCustomers.Position += 1
   End Sub

   Private Sub button3_Click(sender As Object, e As System.EventArgs)
      ' Go to the previous item in the Order list.
      bmOrders.Position -= 1
   End Sub

   Private Sub button4_Click(sender As Object, e As System.EventArgs)
      ' Go to the next item in the Orders list.
      bmOrders.Position += 1
   End Sub

   ' Creates a DataSet with two tables and populates it.
   Private Sub MakeDataSet
      ' Create a DataSet.
      ds = New DataSet("myDataSet")

      ' Creates two DataTables.
      Dim tCust As DataTable = New DataTable("Customers")
      Dim tOrders As DataTable = New DataTable("Orders")

      ' Create two columns, and add them to the first table.
      Dim cCustID As DataColumn = New DataColumn("CustID", _
      System.Type.GetType("System.Int32"))
      Dim cCustName As DataColumn = New DataColumn("CustName")
      tCust.Columns.Add(cCustID)
      tCust.Columns.Add(cCustName)

      ' Create three columns, and add them to the second table.
      Dim cID As DataColumn = _
         New DataColumn("CustID", System.Type.GetType("System.Int32"))
      Dim cOrderDate As DataColumn = _
         New DataColumn("orderDate", System.Type.GetType("System.DateTime"))
      Dim cOrderAmount As DataColumn = _
         New DataColumn("OrderAmount", System.Type.GetType("System.Decimal"))
      tOrders.Columns.Add(cOrderAmount)
      tOrders.Columns.Add(cID)
      tOrders.Columns.Add(cOrderDate)

      ' Add the tables to the DataSet.
      ds.Tables.Add(tCust)
      ds.Tables.Add(tOrders)

      ' Create a DataRelation, and add it to the DataSet.
      Dim dr As DataRelation = New _
         DataRelation("custToOrders", cCustID, cID)
      ds.Relations.Add(dr)
      
      ' Populate the tables. For each customer and orders,
      ' create two DataRow variables.
      Dim newRow1 As DataRow
      Dim newRow2 As DataRow

         ' Create three customers in the Customers Table.
         Dim i As Integer
         For i = 1 to 3
            newRow1 = tCust.NewRow
            newRow1("custID") = i
            ' Adds the row to the Customers table.
            tCust.Rows.Add(newRow1)
         Next

         ' Give each customer a distinct name.
         tCust.Rows(0)("custName") = "Alpha"
         tCust.Rows(1)("custName") = "Beta"
         tCust.Rows(2)("custName") = "Omega"

         ' For each customer, create five rows in the Orders table.
         Dim j As Integer
         For i = 1 to 3
         For j = 1 to 5
            newRow2 = tOrders.NewRow
            newRow2("CustID") = i
            newRow2("orderDate") = New DateTime(2001, i, j * 2)
            newRow2("OrderAmount") = i * 10 + j * .1
            ' Add the row to the Orders table.
            tOrders.Rows.Add(newRow2)
         Next
         Next
   End Sub
End Class
using System;
using System.Data;
using System.Drawing;
using System.Globalization;
using System.Windows.Forms;

public class Form1 : System.Windows.Forms.Form.
{
   private System.ComponentModel.Container components;
   private Button button1;
   private Button button2;
   private Button button3;
   private Button button4;
   private TextBox text1;
   private TextBox text2;
   private TextBox text3;

   private BindingManagerBase bmCustomers;
   private BindingManagerBase bmOrders;
   private DataSet ds;
   private DateTimePicker DateTimePicker1;

   public Form1()
   {
      // Required for Windows Form. Designer support.
      InitializeComponent();
      // Call SetUp to bind the controls.
      SetUp();
   }
 
   private void InitializeComponent()
   {
      // Create the form. and its controls.
      this.components = new System.ComponentModel.Container();
      this.button1 = new System.Windows.Forms.Button();
      this.button2 = new System.Windows.Forms.Button();
      this.button3 = new System.Windows.Forms.Button();
      this.button4 = new System.Windows.Forms.Button();
      
      this.text1= new System.Windows.Forms.TextBox();
      this.text2= new System.Windows.Forms.TextBox();
      this.text3= new System.Windows.Forms.TextBox();
      
      this.DateTimePicker1 = new DateTimePicker();
      
      this.Text = "Binding Sample";
      this.ClientSize = new System.Drawing.Size(450, 200);
      
      button1.Location = new System.Drawing.Point(24, 16);
      button1.Size = new System.Drawing.Size(64, 24);
      button1.Text = "<";
      button1.Click+=new System.EventHandler(button1_Click);

      button2.Location = new System.Drawing.Point(90, 16);
      button2.Size = new System.Drawing.Size(64, 24);
      button2.Text = ">";
      button2.Click+=new System.EventHandler(button2_Click);

      button3.Location = new System.Drawing.Point(90, 100);
      button3.Size = new System.Drawing.Size(64, 24);
      button3.Text = "<";
      button3.Click+=new System.EventHandler(button3_Click);

      button4.Location = new System.Drawing.Point(150, 100);
      button4.Size = new System.Drawing.Size(64, 24);
      button4.Text = ">";
      button4.Click+=new System.EventHandler(button4_Click);

      text1.Location = new System.Drawing.Point(24, 50);
      text1.Size = new System.Drawing.Size(150, 24);

      text2.Location = new System.Drawing.Point(190, 50);
      text2.Size = new System.Drawing.Size(150, 24);

      text3.Location = new System.Drawing.Point(290, 150);
      text3.Size = new System.Drawing.Size(150, 24);
      
      DateTimePicker1.Location = new System.Drawing.Point(90, 150);
      DateTimePicker1.Size = new System.Drawing.Size(200, 800);
      
      this.Controls.Add(button1);
      this.Controls.Add(button2);
      this.Controls.Add(button3);
      this.Controls.Add(button4);
      this.Controls.Add(text1);
      this.Controls.Add(text2);
      this.Controls.Add(text3);
      this.Controls.Add(DateTimePicker1);
   }

   protected override void Dispose( bool disposing ){
      if( disposing ){
         if (components != null){
            components.Dispose();}
      }
      base.Dispose( disposing );
   }
   public static void Main()
   {
      Application.Run(new Form1());
   }
   
   private void SetUp()
   {
      // Create a DataSet with two tables and one relation.
      MakeDataSet();
      BindControls();
   }

   protected void BindControls()
   {
      /* Create two Binding objects for the first two TextBox 
         controls. The data-bound property for both controls 
         is the Text property. The data source is a DataSet 
         (ds). The data member is the  
         "TableName.ColumnName" string. */
      text1.DataBindings.Add(new Binding
      ("Text", ds, "customers.custName"));
      text2.DataBindings.Add(new Binding
      ("Text", ds, "customers.custID"));
      
      /* Bind the DateTimePicker control by adding a new Binding. 
         The data member of the DateTimePicker is a 
         TableName.RelationName.ColumnName string. */
      DateTimePicker1.DataBindings.Add(new 
      Binding("Value", ds, "customers.CustToOrders.OrderDate"));

      /* Add event delegates for the Parse and Format events to a 
         new Binding object, and add the object to the third 
         TextBox control's BindingsCollection. The delegates 
         must be added before adding the Binding to the 
         collection; otherwise, no formatting occurs until 
         the Current object of the BindingManagerBase for 
         the data source changes. */
         Binding b = new Binding
         ("Text", ds, "customers.custToOrders.OrderAmount");
      b.Parse+=new ConvertEventHandler(CurrencyStringToDecimal);
      b.Format+=new ConvertEventHandler(DecimalToCurrencyString);
      text3.DataBindings.Add(b);

      // Get the BindingManagerBase for the Customers table. 
      bmCustomers = this.BindingContext [ds, "Customers"];

      /* Get the BindingManagerBase for the Orders table using the 
         RelationName. */ 
      bmOrders = this.BindingContext[ds, "customers.CustToOrders"];
   }

   private void DecimalToCurrencyString(object sender, ConvertEventArgs cevent)
   {
      /* This method is the Format event handler. Whenever the 
         control displays a new value, the value is converted from 
         its native Decimal type to a string. The ToString method 
         then formats the value as a Currency, by using the 
         formatting character "c". */

      // The application can only convert to string type. 
      if(cevent.DesiredType != typeof(string)) return;

      cevent.Value = ((decimal) cevent.Value).ToString("c");
   }

   private void CurrencyStringToDecimal(object sender, ConvertEventArgs cevent)
   {   
      /* This method is the Parse event handler. The Parse event 
         occurs whenever the displayed value changes. The static 
         ToDecimal method of the Convert class converts the 
         value back to its native Decimal type. */

      // Can only convert to decimal type.
      if(cevent.DesiredType != typeof(decimal)) return;

      cevent.Value = Decimal.Parse(cevent.Value.ToString(),
          NumberStyles.Currency, null);

      /* To see that no precision is lost, print the unformatted 
         value. For example, changing a value to "10.0001" 
         causes the control to display "10.00", but the 
         unformatted value remains "10.0001". */
      Console.WriteLine(cevent.Value);
   }

   private void button1_Click(object sender, System.EventArgs e)
   {
      // Go to the previous item in the Customer list.
      bmCustomers.Position -= 1;
   }

   private void button2_Click(object sender, System.EventArgs e)
   {
      // Go to the next item in the Customer list.
      bmCustomers.Position += 1;
   }
    
   private void button3_Click(object sender, System.EventArgs e)
   {
      // Go to the previous item in the Orders list.
      bmOrders.Position-=1;
   }

   private void button4_Click(object sender, System.EventArgs e)
   {
      // Go to the next item in the Orders list.
      bmOrders.Position+=1;
   }

   // Create a DataSet with two tables and populate it.
   private void MakeDataSet()
   {
      // Create a DataSet.
      ds = new DataSet("myDataSet");
      
      // Create two DataTables.
      DataTable tCust = new DataTable("Customers");
      DataTable tOrders = new DataTable("Orders");

      // Create two columns, and add them to the first table.
      DataColumn cCustID = new DataColumn("CustID", typeof(int));
      DataColumn cCustName = new DataColumn("CustName");
      tCust.Columns.Add(cCustID);
      tCust.Columns.Add(cCustName);

      // Create three columns, and add them to the second table.
      DataColumn cID = 
         new DataColumn("CustID", typeof(int));
      DataColumn cOrderDate = 
         new DataColumn("orderDate",typeof(DateTime));
      DataColumn cOrderAmount = 
         new DataColumn("OrderAmount", typeof(decimal));
      tOrders.Columns.Add(cOrderAmount);
      tOrders.Columns.Add(cID);
      tOrders.Columns.Add(cOrderDate);

      // Add the tables to the DataSet.
      ds.Tables.Add(tCust);
      ds.Tables.Add(tOrders);

      // Create a DataRelation, and add it to the DataSet.
      DataRelation dr = new DataRelation
      ("custToOrders", cCustID , cID);
      ds.Relations.Add(dr);
   
      /* Populate the tables. For each customer and order, 
         create two DataRow variables. */
      DataRow newRow1;
      DataRow newRow2;

      
                                                    来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/12639172/viewspace-157071/,如需转载,请注明出处,否则将追究法律责任。
                                            

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