Binding Classe

Definizione

Rappresenta l'associazione semplice tra il valore della proprietà di un oggetto e il valore della proprietà di un controllo.Represents the simple binding between the property value of an object and the property value of a control.

public ref class Binding
[System.ComponentModel.TypeConverter(typeof(System.Windows.Forms.ListBindingConverter))]
public class Binding
type Binding = class
Public Class Binding
Ereditarietà
Binding
Attributi

Esempi

Nell'esempio di codice seguente viene creato un Windows Form con diversi controlli che dimostrano data binding semplici.The following code example creates a Windows Form with several controls that demonstrate simple data binding. Nell'esempio viene creato un DataSet con due tabelle denominate Customers e Orders e un DataRelation denominato custToOrders.The example creates a DataSet with two tables named Customers and Orders, and a DataRelation named custToOrders. Quattro controlli (un DateTimePicker e tre controlli TextBox) sono associati ai dati delle colonne delle tabelle.Four controls (a DateTimePicker and three TextBox controls) are data bound to columns in the tables. Per ogni controllo, nell'esempio viene creato e aggiunto un Binding al controllo tramite la proprietà DataBindings.For each control, the example creates and adds a Binding to the control through the DataBindings property. Nell'esempio viene restituito un BindingManagerBase per ogni tabella tramite il BindingContext del modulo.The example returns a BindingManagerBase for each table through the form's BindingContext. Quattro Button controllano l'incremento o il decremento della proprietà Position negli oggetti BindingManagerBase.Four Button controls increment or decrement the Position property on the BindingManagerBase objects.

#using <system.dll>
#using <system.data.dll>
#using <system.drawing.dll>
#using <system.windows.forms.dll>
#using <system.xml.dll>

using namespace System;
using namespace System::Data;
using namespace System::Drawing;
using namespace System::Globalization;
using namespace System::Windows::Forms;

#define null 0L
public ref class Form1: public Form
{
private:
   System::ComponentModel::Container^ components;
   Button^ button1;
   Button^ button2;
   Button^ button3;
   Button^ button4;
   TextBox^ text1;
   TextBox^ text2;
   TextBox^ text3;
   BindingManagerBase^ bmCustomers;
   BindingManagerBase^ bmOrders;
   DataSet^ ds;
   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 = gcnew System::ComponentModel::Container;
      this->button1 = gcnew Button;
      this->button2 = gcnew Button;
      this->button3 = gcnew Button;
      this->button4 = gcnew Button;
      this->text1 = gcnew TextBox;
      this->text2 = gcnew TextBox;
      this->text3 = gcnew TextBox;
      this->DateTimePicker1 = gcnew DateTimePicker;
      this->Text =  "Binding Sample";
      this->ClientSize = System::Drawing::Size( 450, 200 );
      button1->Location = System::Drawing::Point( 24, 16 );
      button1->Size = System::Drawing::Size( 64, 24 );
      button1->Text =  "<";
      button1->Click += gcnew System::EventHandler( this, &Form1::button1_Click );
      button2->Location = System::Drawing::Point( 90, 16 );
      button2->Size = System::Drawing::Size( 64, 24 );
      button2->Text =  ">";
      button2->Click += gcnew System::EventHandler( this, &Form1::button2_Click );
      button3->Location = System::Drawing::Point( 90, 100 );
      button3->Size = System::Drawing::Size( 64, 24 );
      button3->Text =  "<";
      button3->Click += gcnew System::EventHandler( this, &Form1::button3_Click );
      button4->Location = System::Drawing::Point( 150, 100 );
      button4->Size = System::Drawing::Size( 64, 24 );
      button4->Text =  ">";
      button4->Click += gcnew System::EventHandler( this, &Form1::button4_Click );
      text1->Location = System::Drawing::Point( 24, 50 );
      text1->Size = System::Drawing::Size( 150, 24 );
      text2->Location = System::Drawing::Point( 190, 50 );
      text2->Size = System::Drawing::Size( 150, 24 );
      text3->Location = System::Drawing::Point( 290, 150 );
      text3->Size = System::Drawing::Size( 150, 24 );
      DateTimePicker1->Location = System::Drawing::Point( 90, 150 );
      DateTimePicker1->Size = 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 );
   }

public:
   ~Form1()
   {
      if ( components != nullptr )
      {
         delete components;
      }
   }

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( gcnew Binding( "Text",ds,"customers.custName" ) );
      text2->DataBindings->Add( gcnew 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( gcnew 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 = gcnew Binding( "Text",ds,"customers.custToOrders.OrderAmount" );
      b->Parse += gcnew ConvertEventHandler( this, &Form1::CurrencyStringToDecimal );
      b->Format += gcnew ConvertEventHandler( this, &Form1::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 != String::typeid )
            return;

      cevent->Value = (dynamic_cast<Decimal^>(cevent->Value))->ToString( "c" );
   }

   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 != Decimal::typeid )
            return;

      cevent->Value = Decimal::Parse( cevent->Value->ToString(), NumberStyles::Currency, nullptr );
      
      /* 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;
   }

   void button2_Click( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      // Go to the next item in the Customer list.
      bmCustomers->Position += 1;
   }

   void button3_Click( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      
      // Go to the previous item in the Orders list.
      bmOrders->Position = bmOrders->Position - 1;
   }

   void button4_Click( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      
      // Go to the next item in the Orders list.
      bmOrders->Position = bmOrders->Position + 1;
   }

private:

   // Create a DataSet with two tables and populate it.
   void MakeDataSet()
   {
      // Create a DataSet.
      ds = gcnew DataSet( "myDataSet" );

      // Create two DataTables.
      DataTable^ tCust = gcnew DataTable( "Customers" );
      DataTable^ tOrders = gcnew DataTable( "Orders" );

      // Create two columns, and add them to the first table.
      DataColumn^ cCustID = gcnew DataColumn( "CustID",Int32::typeid );
      DataColumn^ cCustName = gcnew DataColumn( "CustName" );
      tCust->Columns->Add( cCustID );
      tCust->Columns->Add( cCustName );

      // Create three columns, and add them to the second table.
      DataColumn^ cID = gcnew DataColumn( "CustID",Int32::typeid );
      DataColumn^ cOrderDate = gcnew DataColumn( "orderDate",DateTime::typeid );
      DataColumn^ cOrderAmount = gcnew DataColumn( "OrderAmount",Decimal::typeid );
      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 = gcnew DataRelation( "custToOrders",cCustID,cID );
      ds->Relations->Add( dr );
      
      /* Populate the tables. For each customer and order, 
              create two DataRow variables. */
      DataRow^ newRow1; // = new DataRow();

      DataRow^ newRow2; // = new DataRow();

      // Create three customers in the Customers Table.
      for ( int i = 1; i < 4; i++ )
      {
         newRow1 = tCust->NewRow();
         newRow1[ "custID" ] = i;
         
         // Add the row to the Customers table.
         tCust->Rows->Add( newRow1 );

      }
      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.
      for ( int i = 1; i < 4; i++ )
      {
         for ( int j = 1; j < 6; j++ )
         {
            newRow2 = tOrders->NewRow();
            newRow2[ "CustID" ] = i;
            newRow2[ "orderDate" ] = System::DateTime( 2001, i, j * 2 );
            newRow2[ "OrderAmount" ] = i * 10 + j * .1;
            
            // Add the row to the Orders table.
            tOrders->Rows->Add( newRow2 );
         }
      }
   }
};

int main()
{
   Application::Run( gcnew Form1 );
}
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;

      // Create three customers in the Customers Table.
      for(int i = 1; i < 4; i++)
      {
         newRow1 = tCust.NewRow();
         newRow1["custID"] = i;
         // Add the row to the Customers table.
         tCust.Rows.Add(newRow1);
      }
      // 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.
      for(int i = 1; i < 4; i++)
      {
         for(int j = 1; j < 6; j++)
         {
            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);
         }
      }
   }
 }

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 (components IsNot 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 cevent.DesiredType IsNot 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 cevent.DesiredType IsNot 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

Commenti

Usare la classe Binding per creare e gestire un'associazione semplice tra la proprietà di un controllo e la proprietà di un oggetto o la proprietà dell'oggetto corrente in un elenco di oggetti.Use the Binding class to create and maintain a simple binding between the property of a control and either the property of an object, or the property of the current object in a list of objects.

Come esempio del primo caso, è possibile associare la proprietà Text di un controllo TextBox alla proprietà FirstName di un oggetto Customer.As an example of the first case, you can bind the Text property of a TextBox control to the FirstName property of a Customer object. Come esempio del secondo caso, è possibile associare la proprietà Text di un controllo TextBox alla proprietà FirstName di un DataTable che contiene i clienti.As an example of the second case, you can bind the Text property of a TextBox control to the FirstName property of a DataTable that contains customers.

La classe Binding consente inoltre di formattare i valori per la visualizzazione tramite l'evento Format e di recuperare i valori formattati tramite l'evento Parse.The Binding class also enables you to format values for display through the Format event and to retrieve formatted values through the Parse event.

Quando si crea un'istanza Binding con il costruttore Binding, è necessario specificare tre elementi:When constructing a Binding instance with Binding constructor, you must specify three items:

  • Nome della proprietà del controllo a cui eseguire l'associazione.The name of the control property to bind to.

  • Origine dati.The data source.

  • Percorso di navigazione che viene risolto in un elenco o in una proprietà nell'origine dati.The navigation path that resolves to a list or property in the data source. Il percorso di navigazione viene utilizzato anche per creare la proprietà BindingMemberInfo dell'oggetto.The navigation path is also used to create the object's BindingMemberInfo property.

In primo luogo, è necessario specificare il nome della proprietà del controllo a cui si desidera associare i dati.First, you must specify name of the control property you want to bind the data to. Per visualizzare, ad esempio, i dati in un controllo TextBox, specificare la proprietà Text.For example, to display data in a TextBox control, specify the Text property.

In secondo luogo, è possibile specificare un'istanza di una delle classi della tabella seguente come origine dati.Second, you can specify an instance of any one of the classes in the following table as the data source.

DescriptionDescription Esempio in C#C# example
Qualsiasi classe che implementa IBindingList o ITypedList.Any class that implements IBindingList or ITypedList. Sono incluse le seguenti: DataSet, DataTable, DataView o DataViewManager.These include the following: DataSet, DataTable, DataView, or DataViewManager. DataSet ds = new DataSet("myDataSet");
Qualsiasi classe che implementa IList per creare una raccolta indicizzata di oggetti.Any class that implements IList to create an indexed collection of objects. La raccolta deve essere creata e riempita prima di creare il Binding.The collection must be created and filled before creating the Binding. Gli oggetti nell'elenco devono essere tutti dello stesso tipo. in caso contrario, verrà generata un'eccezione.The objects in the list must all be of the same type; otherwise, an exception will be thrown. ArrayList ar1 = new ArrayList; Customer1 cust1 = new Customer("Louis"); ar1.Add(cust1);
Oggetto IList fortemente tipizzato di oggetti fortemente tipizzatiA strongly typed IList of strongly typed objects Customer [] custList = new Customer[3];

In terzo luogo, è necessario specificare il percorso di navigazione, che può essere una stringa vuota (""), un singolo nome di proprietà o una gerarchia di nomi delimitati da punti.Third, you must specify the navigation path, which can be an empty string (""), a single property name, or a period-delimited hierarchy of names. Se si imposta il percorso di navigazione su una stringa vuota, il metodo ToString verrà chiamato sull'oggetto origine dati sottostante.If you set the navigation path to an empty string, the ToString method will be called on the underlying data source object.

Se l'origine dati è un DataTable, che può contenere più oggetti DataColumn, il percorso di navigazione deve essere utilizzato per la risoluzione in una colonna specifica.If the data source is a DataTable, which can contain multiple DataColumn objects, the navigation path must be used to resolve to a specific column.

Nota

Quando l'origine dati è un DataSet, DataViewManager o DataTable, si sta effettivamente eseguendo l'associazione a un DataView.When the data source is a DataSet, DataViewManager, or DataTable, you are actually binding to a DataView. Di conseguenza, le righe associate sono effettivamente oggetti DataRowView.Consequently, the bound rows are actually DataRowView objects.

Un percorso di navigazione delimitato da punti è obbligatorio quando l'origine dati è impostata su un oggetto che contiene più oggetti DataTable, ad esempio un DataSet o DataViewManager.A period-delimited navigation path is required when the data source is set to an object that contains multiple DataTable objects (such as a DataSet or DataViewManager). È anche possibile usare un percorso di navigazione delimitato da punti quando si esegue l'associazione a un oggetto le cui proprietà restituiscono riferimenti ad altri oggetti, ad esempio una classe con proprietà che restituiscono altri oggetti classe.You can also use a period-delimited navigation path when you bind to an object whose properties return references to other objects (such as a class with properties that return other class objects). Ad esempio, i percorsi di navigazione seguenti descrivono tutti i campi dati validi:For example, the following navigation paths all describe valid data fields:

  • "Size. Height""Size.Height"

  • "Suppliers.CompanyName""Suppliers.CompanyName"

  • "Regions.regionsToCustomers.CustomerFirstName""Regions.regionsToCustomers.CustomerFirstName"

  • "Regions.regionsToCustomers.customersToOrders.ordersToDetails.Quantity""Regions.regionsToCustomers.customersToOrders.ordersToDetails.Quantity"

Ogni membro del percorso può restituire una proprietà che viene risolta in un singolo valore, ad esempio un numero intero, o un elenco di valori (ad esempio una matrice di stringhe).Each member of the path can return either a property that resolves to a single value (such as an integer), or a list of values (such as an array of strings). Sebbene ogni membro nel percorso possa essere un elenco o una proprietà, il membro finale deve risolversi in una proprietà.Although each member in the path can be a list or property, the final member must resolve to a property. Ogni membro si basa sul membro precedente: "Size. Height" viene risolto nella proprietà Height per l'@no__t corrente-1; "Regions. regionsToCustomers. CustomerFirstName" viene risolto con il nome per il cliente corrente, in cui il cliente è uno dei clienti per l'area corrente.Each member builds on the previous member: "Size.Height" resolves to the Height property for the current Size; "Regions.regionsToCustomers.CustomerFirstName" resolves to the first name for the current customer, where the customer is one of the customers for the current region.

Un DataRelation restituisce un elenco di valori collegando un DataTable a un secondo DataTable in un DataSet.A DataRelation returns a list of values by linking one DataTable to a second DataTable in a DataSet. Se il DataSet contiene oggetti DataRelation, è possibile specificare il membro dati come TableName seguito da un RelationName, quindi da un ColumnName.If the DataSet contains DataRelation objects, you can specify the data member as a TableName followed by a RelationName, and then a ColumnName. Se, ad esempio, il DataTable denominato "Suppliers" contiene un DataRelation denominato "suppliers2products", il membro dati potrebbe essere "Suppliers. suppliers2products. ProductName".For example, if the DataTable named "Suppliers" contains a DataRelation named "suppliers2products", the data member could be "Suppliers.suppliers2products.ProductName".

L'origine dati può essere costituita da un set di classi correlate.The data source can consist of a set of related classes. Si supponga, ad esempio, un set di classi che cataloga i sistemi solari.For example, imagine a set of classes that catalogs solar systems. La classe denominata System contiene una proprietà denominata Stars che restituisce una raccolta di oggetti Star.The class named System contains a property named Stars that returns a collection of Star objects. Ogni oggetto Star ha proprietà Name e Mass, oltre a una proprietà Planets che restituisce una raccolta di oggetti Planet.Each Star object has Name and Mass properties, as well as a Planets property that returns a collection of Planet objects. In questo sistema ogni pianeta ha anche proprietà Mass e Name.In this system, each planet also has Mass and Name properties. Ogni oggetto Planet ha una proprietà Moons che restituisce una raccolta di oggetti Moon, ognuno dei quali ha anche proprietà Name e Mass.Each Planet object further has a Moons property that returns a collection of Moon objects, each of which also has Name and Mass properties. Se si specifica un oggetto System come origine dati, è possibile specificare uno dei seguenti elementi come membro dati:If you specify a System object as the data source, you can specify any of the following as the data member:

  • "Stars.Name""Stars.Name"

  • "Stars. Mass""Stars.Mass"

  • "Stars.Planets.Name""Stars.Planets.Name"

  • "Stars. Pianetis. Mass""Stars.Planets.Mass"

  • "Stars.Planets.Moons.Name""Stars.Planets.Moons.Name"

  • "Stars.Planets.Moons.Mass""Stars.Planets.Moons.Mass"

I controlli che possono essere con associazione semplice includono una raccolta di oggetti Binding in un ControlBindingsCollection, a cui è possibile accedere tramite la proprietà DataBindings del controllo.Controls that can be simple-bound feature a collection of Binding objects in a ControlBindingsCollection, which you can access through the control's DataBindings property. Per aggiungere un Binding alla raccolta, chiamare il metodo Add, associando quindi una proprietà del controllo a una proprietà di un oggetto o a una proprietà dell'oggetto corrente in un elenco.You add a Binding to the collection by calling the Add method, thereby binding a property of the control to a property of an object (or to a property of the current object in a list).

È possibile eseguire l'associazione semplice a qualsiasi oggetto che deriva dalla classe System.Windows.Forms.Control, ad esempio, i controlli Windows seguenti:You can simple-bind to any object that derives from the System.Windows.Forms.Control class, for example, the following Windows controls:

Nota

Solo la proprietà SelectedValue del controllo ComboBox, CheckedListBox e ListBox è con associazione semplice.Only the SelectedValue property of the ComboBox, CheckedListBox, and ListBox control is simple bound.

La classe BindingManagerBase è una classe astratta che gestisce tutti gli oggetti Binding per un'origine dati e un membro dati specifici.The BindingManagerBase class is an abstract class that manages all the Binding objects for a particular data source and data member. Le classi che derivano da BindingManagerBase sono le classi CurrencyManager e PropertyManager.Classes that derive from BindingManagerBase are the CurrencyManager and the PropertyManager classes. La modalità di gestione di un Binding varia a seconda che il Binding sia un'associazione di tipo elenco o un'associazione di proprietà.How a Binding is managed depends on whether the Binding is a list binding or a property binding. Ad esempio, se si tratta di un'associazione di elenco, è possibile utilizzare il BindingManagerBase per specificare un Position nell'elenco; il Position, pertanto, determina quale elemento (da tutti gli elementi nell'elenco) è effettivamente associato a un controllo.For example, if it is a list binding, you can use the BindingManagerBase to specify a Position in the list; the Position, therefore, determines which item (out of all items in the list) is actually bound to a control. Per restituire il BindingManagerBase appropriato, usare il BindingContext.To return the appropriate BindingManagerBase, use the BindingContext.

Per aggiungere una nuova riga a un set di controlli associato allo stesso DataSource, usare il metodo AddNew della classe BindingManagerBase.To add a new row to a set of controls bound to the same DataSource, use the AddNew method of the BindingManagerBase class. Utilizzare la proprietà Item[Object] della classe BindingContext per restituire il CurrencyManager appropriato.Use the Item[Object] property of the BindingContext class to return the appropriate CurrencyManager. Per evitare l'aggiunta della nuova riga, usare il metodo CancelCurrentEdit.To escape the addition of the new row, use the CancelCurrentEdit method.

Costruttori

Binding(String, Object, String)

Inizializza una nuova istanza della classe Binding che stabilisce un'associazione semplice tra la proprietà del controllo indicata e il membro dati specificato dell'origine dati.Initializes a new instance of the Binding class that simple-binds the indicated control property to the specified data member of the data source.

Binding(String, Object, String, Boolean)

Inizializza una nuova istanza della classe Binding che stabilisce un'associazione tra la proprietà del controllo indicata e il membro dati specificato dell'origine dati, consentendo inoltre l'applicazione della formattazione, se richiesta.Initializes a new instance of the Binding class that binds the indicated control property to the specified data member of the data source, and optionally enables formatting to be applied.

Binding(String, Object, String, Boolean, DataSourceUpdateMode)

Inizializza una nuova istanza della classe Binding che stabilisce un'associazione semplice tra la proprietà del controllo specificato e il membro dati specificato dell'origine dati specificata.Initializes a new instance of the Binding class that binds the specified control property to the specified data member of the specified data source. Se richiesto, consente la formattazione e la propagazione dei valori nell'origine dati in base all'impostazione di aggiornamento specificata.Optionally enables formatting and propagates values to the data source based on the specified update setting.

Binding(String, Object, String, Boolean, DataSourceUpdateMode, Object)

Inizializza una nuova istanza della classe Binding che stabilisce un'associazione tra la proprietà del controllo e il membro dati specificati dell'origine dati indicata.Initializes a new instance of the Binding class that binds the indicated control property to the specified data member of the specified data source. Se richiesto, abilita la formattazione, propaga i valori nell'origine dati in base all'impostazione di aggiornamento specificata e imposta la proprietà sul valore specificato quando l'origine dati restituisce DBNull.Optionally enables formatting, propagates values to the data source based on the specified update setting, and sets the property to the specified value when a DBNull is returned from the data source.

Binding(String, Object, String, Boolean, DataSourceUpdateMode, Object, String)

Inizializza una nuova istanza della classe Binding che stabilisce un'associazione semplice tra la proprietà del controllo specificato e il membro dati specificato dell'origine dati specificata.Initializes a new instance of the Binding class that binds the specified control property to the specified data member of the specified data source. Se richiesto, abilita la formattazione con la stringa di formato specificata, propaga i valori nell'origine dati in base all'impostazione di aggiornamento specificata e imposta la proprietà sul valore specificato quando l'origine dati restituisce un valore DBNull.Optionally enables formatting with the specified format string; propagates values to the data source based on the specified update setting; and sets the property to the specified value when a DBNull is returned from the data source.

Binding(String, Object, String, Boolean, DataSourceUpdateMode, Object, String, IFormatProvider)

Inizializza una nuova istanza della classe Binding con proprietà del controllo specificato sul membro dati specificato dell'origine dati specificata.Initializes a new instance of the Binding class with the specified control property to the specified data member of the specified data source. Se richiesto, abilita la formattazione con la stringa di formato specificata; propaga i valori nell'origine dati in base all'impostazione di aggiornamento specificata; abilita la formattazione con la stringa di formato specificata e imposta la proprietà sul valore specificato quando l'origine dati restituisce DBNull nonché imposta il provider del formato specificato.Optionally enables formatting with the specified format string; propagates values to the data source based on the specified update setting; enables formatting with the specified format string; sets the property to the specified value when a DBNull is returned from the data source; and sets the specified format provider.

Proprietà

BindableComponent

Ottiene il controllo cui è associato l'oggetto Binding.Gets the control the Binding is associated with.

BindingManagerBase

Ottiene l'oggetto BindingManagerBase per l'oggetto Binding.Gets the BindingManagerBase for this Binding.

BindingMemberInfo

Ottiene un oggetto che contiene informazioni su questa associazione in base al parametro dataMember nel costruttore Binding.Gets an object that contains information about this binding based on the dataMember parameter in the Binding constructor.

Control

Ottiene il controllo a cui appartiene l'associazione.Gets the control that the binding belongs to.

ControlUpdateMode

Ottiene o imposta un valore che indica quando le modifiche apportate all'origine dati verranno propagate nella proprietà del controllo associata.Gets or sets when changes to the data source are propagated to the bound control property.

DataSource

Ottiene l'origine dati per questa associazione.Gets the data source for this binding.

DataSourceNullValue

Ottiene o imposta il valore da memorizzare nell'origine dati se il valore del controllo e null oppure vuoto.Gets or sets the value to be stored in the data source if the control value is null or empty.

DataSourceUpdateMode

Ottiene o imposta un valore che indica quando le modifiche apportate alla proprietà del controllo associata verranno propagate nell'origine dati.Gets or sets a value that indicates when changes to the bound control property are propagated to the data source.

FormatInfo

Ottiene o imposta l'oggetto IFormatProvider che fornisce il comportamento personalizzato della formattazione.Gets or sets the IFormatProvider that provides custom formatting behavior.

FormatString

Ottiene o imposta i caratteri identificatori di formato che indicano il modo in cui deve essere visualizzato un valore.Gets or sets the format specifier characters that indicate how a value is to be displayed.

FormattingEnabled

Ottiene o imposta un valore che indica se la conversione del tipo e la formattazione vengono applicate ai dati della proprietà del controllo.Gets or sets a value indicating whether type conversion and formatting is applied to the control property data.

IsBinding

Ottiene un valore che indica se l'associazione è attiva.Gets a value indicating whether the binding is active.

NullValue

Ottiene o imposta l'oggetto Object da impostare come proprietà del controllo quando l'origine dati contiene un valore DBNull.Gets or sets the Object to be set as the control property when the data source contains a DBNull value.

PropertyName

Ottiene il nome della proprietà con associazione a dati del controllo.Gets the name of the control's data-bound property.

Metodi

Equals(Object)

Determina se l'oggetto specificato è uguale all'oggetto corrente.Determines whether the specified object is equal to the current object.

(Ereditato da Object)
GetHashCode()

Funge da funzione hash predefinita.Serves as the default hash function.

(Ereditato da Object)
GetType()

Ottiene l'oggetto Type dell'istanza corrente.Gets the Type of the current instance.

(Ereditato da Object)
MemberwiseClone()

Crea una copia superficiale dell'oggetto Object corrente.Creates a shallow copy of the current Object.

(Ereditato da Object)
OnBindingComplete(BindingCompleteEventArgs)

Genera l'evento BindingComplete.Raises the BindingComplete event.

OnFormat(ConvertEventArgs)

Genera l'evento Format.Raises the Format event.

OnParse(ConvertEventArgs)

Genera l'evento Parse.Raises the Parse event.

ReadValue()

Imposta la proprietà del controllo sul valore letto dall'origine dati.Sets the control property to the value read from the data source.

ToString()

Restituisce una stringa che rappresenta l'oggetto corrente.Returns a string that represents the current object.

(Ereditato da Object)
WriteValue()

Legge il valore corrente dalla proprietà del controllo e lo scrive nell'origine dati.Reads the current value from the control property and writes it to the data source.

Eventi

BindingComplete

Si verifica quando la proprietà FormattingEnabled viene impostata su true e un'operazione di associazione viene completata, ad esempio quando i dati vengono spostati dal controllo all'origine dati o viceversa.Occurs when the FormattingEnabled property is set to true and a binding operation is complete, such as when data is pushed from the control to the data source or vice versa.

Format

Si verifica quando la proprietà di un controllo viene associata a un valore di dati.Occurs when the property of a control is bound to a data value.

Parse

Si verifica quando viene modificato il valore di un controllo associato a dati.Occurs when the value of a data-bound control changes.

Si applica a

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