BindingContext Classe

Definizione

public ref class BindingContext : System::Collections::ICollection

public class BindingContext : System.Collections.ICollection

type BindingContext = class
    interface ICollection
    interface IEnumerable

Public Class BindingContext
Implements ICollection

Ereditarietà

Object

BindingContext

Implementazioni

ICollection IEnumerable

Esempio

Nell'esempio di codice seguente vengono creati quattro Binding oggetti per associare cinque controlli, a DateTimePicker e quattro TextBox controlli, a diverse origini dati.The following code example creates four Binding objects to bind five controls - a DateTimePicker and four TextBox controls - to several data sources. BindingContextViene quindi usato per ottenere BindingManagerBase per ogni origine dati.The BindingContext is then used to get the BindingManagerBase for each data source.

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 a navigation path in the form: 
         "TableName.ColumnName". */
   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 navigation path:
         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"];

   /* Bind the fourth TextBox control's Text property to the
      third control's Text property. */
   text4->DataBindings->Add( "Text", text3, "Text" );
}

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 a navigation path in the form: 
      "TableName.ColumnName". */
   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 navigation path:
      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"];

   /* Bind the fourth TextBox control's Text property to the
   third control's Text property. */
   text4.DataBindings.Add("Text", text3, "Text");
}

Protected 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 string 
   '   "TableName.ColumnName".
   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,  New ConvertEventHandler(AddressOf CurrencyStringToDecimal)      
   AddHandler b.Format, New ConvertEventHandler(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")

   ' Bind the fourth TextBox control's Text property to the
   ' third control's Text property.
   text4.DataBindings.Add("Text", text3, "Text")

End Sub

Commenti

Ogni Windows Form dispone di almeno un BindingContext oggetto che gestisce gli BindingManagerBase oggetti per il form.Each Windows Form has at least one BindingContext object that manages the BindingManagerBase objects for the form. Poiché la BindingManagerBase classe è astratta, il tipo restituito della Item[] proprietà è CurrencyManager o PropertyManager .Because the BindingManagerBase class is abstract, the return type of the Item[] property is either a CurrencyManager or a PropertyManager. Se l'origine dati è un oggetto che può restituire solo una singola proprietà, anziché un elenco di oggetti, Type è un PropertyManager .If the data source is an object that can return only a single property (instead of a list of objects), the Type is a PropertyManager. Se ad esempio si specifica TextBox come origine dati, viene restituito un oggetto PropertyManager .For example, if you specify a TextBox as the data source, a PropertyManager is returned. D'altra parte, se l'origine dati è un oggetto che implementa IList o IBindingList , CurrencyManager viene restituito un.On the other hand, if the data source is an object that implements IList or IBindingList, a CurrencyManager is returned.

Per ogni origine dati in un Windows Form, è presente una singola CurrencyManager o PropertyManager .For each data source on a Windows Form, there is a single CurrencyManager or PropertyManager. Poiché possono essere presenti più origini dati associate a un Windows Form, BindingContext consente di recuperare qualsiasi particolare associato a CurrencyManager un'origine dati.Because there may be multiple data sources associated with a Windows Form, the BindingContext enables you to retrieve any particular CurrencyManager associated with a data source.

Se si usa un controllo contenitore, ad esempio GroupBox , Panel o TabControl , per contenere controlli con associazione a dati, è possibile creare un oggetto BindingContext solo per quel controllo contenitore e i relativi controlli.If you use a container control, such as a GroupBox, Panel, or TabControl, to contain data-bound controls, you can create a BindingContext for just that container control and its controls. Ogni parte del form può quindi essere gestita autonomamente BindingManagerBase .Then, each part of your form can be managed by its own BindingManagerBase. BindingContextPer ulteriori informazioni sulla creazione BindingManagerBase di più oggetti per la stessa origine dati, vedere il costruttore.See the BindingContext constructor for more information about creating multiple BindingManagerBase objects for the same data source.

Se si aggiunge un TextBox controllo a un form e lo si associa a una colonna di una tabella in un set di dati, il controllo comunica con l'oggetto BindingContext di tale form.If you add a TextBox control to a form and bind it to a column of a table in a dataset, the control communicates with the BindingContext of that form. BindingContext, A sua volta, comunica con l'oggetto specifico CurrencyManager per l'associazione dati.The BindingContext, in turn, talks to the specific CurrencyManager for that data association. Se è stata eseguita una query sulla Position proprietà di CurrencyManager , verrebbe segnalato il record corrente per l'associazione di tale TextBox controllo.If you queried the Position property of the CurrencyManager, it would report the current record for the binding of that TextBox control. Nell'esempio di codice seguente un TextBox controllo viene associato alla FirstName colonna di una Customers tabella nel dataSet1 set di dati tramite l'oggetto BindingContext per il form in cui si trova.In the following code example, a TextBox control is bound to the FirstName column of a Customers table on the dataSet1 dataset through the BindingContext for the form it is on.

TextBox1.DataBindings.Add("Text", dataSet1, "Customers.FirstName")  

textBox1.DataBindings.Add("Text", dataSet1, "Customers.FirstName");  

textBox1->DataBindings->Add("Text", dataSet1, "Customers.FirstName");  

È possibile aggiungere un secondo TextBox controllo ( TextBox2 ) al form e associarlo alla LastName colonna della Customers tabella nello stesso set di dati.You can add a second TextBox control (TextBox2) to the form and bind it to the LastName column of the Customers table in the same dataset. BindingContextÈ a conoscenza del primo binding ( TextBox1 a Customers.FirstName ), quindi utilizzerebbe lo stesso CurrencyManager oggetto, perché entrambe le caselle di testo sono associate allo stesso set di dati ( DataSet1 ).The BindingContext is aware of the first binding (TextBox1 to Customers.FirstName), so it would use the same CurrencyManager, as both text boxes are bound to the same dataset (DataSet1).

TextBox2.DataBindings.Add("Text", dataSet1, "Customers.LastName")  

textBox2.DataBindings.Add("Text", dataSet1, "Customers.LastName");  

textBox2->DataBindings->Add("Text", dataSet1, "Customers.LastName");  

Se si esegue TextBox2 l'associazione a un set di dati diverso, il BindingContext Crea e gestisce un secondo CurrencyManager .If you bind TextBox2 to a different dataset, the BindingContext creates and manages a second CurrencyManager.

È importante essere coerenti sulla modalità di impostazione delle DataSource DisplayMember proprietà e; in caso contrario, BindingContext crea più gestori di valuta per lo stesso set di dati, causando errori.It is important to be consistent about how you set the DataSource and DisplayMember properties; otherwise, the BindingContext creates multiple currency managers for the same dataset, which results in errors. Nell'esempio di codice seguente vengono illustrati alcuni modi per impostare le proprietà e i relativi BindingContext oggetti associati.The following code example shows a few ways to set the properties and their associated BindingContext objects. È possibile impostare le proprietà usando uno dei metodi seguenti, purché siano coerenti in tutto il codice.You can set the properties using either of the following methods, as long as you are consistent throughout your code.

ComboBox1.DataSource = DataSet1  
ComboBox1.DisplayMember = "Customers.FirstName"  
Me.BindingContext(dataSet1, "Customers").Position = 1  

comboBox1.DataSource = DataSet1;  
comboBox1.DisplayMember = "Customers.FirstName";  
this.BindingContext[dataSet1, "Customers"].Position = 1;  

comboBox1->DataSource = dataSet1;  
comboBox1->DisplayMember = "Customers.FirstName";  
this->BindingContext->get_Item(dataSet1, "Customers")->Position = 1;  

ComboBox1.DataSource = DataSet1.Customers  
ComboBox1.DisplayMember = "FirstName"  
Me.BindingContext(dataSet1.Customers).Position = 1  

comboBox1.DataSource = DataSet1.Customers;  
comboBox1.DisplayMember = "FirstName";  
this.BindingContext[dataSet1.Customers].Position = 1;  

comboBox1->DataSource = dataSet1->Customers;  
comboBox1->DisplayMember = "FirstName";  
this->BindingContext->get_Item(dataSet1->Customers)->Position = 1;  

Costruttori

Proprietà

Metodi

Eventi

Implementazioni dell'interfaccia esplicita

Metodi di estensione

Si applica a

Vedi anche

• BindingManagerBase
• Binding
• BindingsCollection