Procedura: implementare l'interfaccia INotifyPropertyChanged
Aggiornamento: novembre 2007
Nell'esempio di codice riportato di seguito viene illustrato come implementare l'interfaccia INotifyPropertyChanged. Implementare questa interfaccia negli oggetti business utilizzati nell'associazione dati dei Windows Form. Se implementata, l'interfaccia consente di comunicare a un controllo associato le modifiche delle proprietà in un oggetto business.
Esempio
' This class implements a simple customer type
' that implements the IPropertyChange interface.
Public Class DemoCustomer
Implements INotifyPropertyChanged
' These fields hold the values for the public properties.
Private idValue As Guid = Guid.NewGuid()
Private customerName As String = String.Empty
Private companyNameValue As String = String.Empty
Private phoneNumberValue As String = String.Empty
Public Event PropertyChanged As PropertyChangedEventHandler _
Implements INotifyPropertyChanged.PropertyChanged
Private Sub NotifyPropertyChanged(ByVal info As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(info))
End Sub
' The constructor is private to enforce the factory pattern.
Private Sub New()
customerName = "no data"
companyNameValue = "no data"
phoneNumberValue = "no data"
End Sub 'New
' This is the public factory method.
Public Shared Function CreateNewCustomer() As DemoCustomer
Return New DemoCustomer()
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 CompanyName() As String
Get
Return Me.companyNameValue
End Get
Set
If value <> Me.companyNameValue Then
Me.companyNameValue = value
NotifyPropertyChanged("CompanyName")
End If
End Set
End Property
Public Property PhoneNumber() As String
Get
Return Me.phoneNumberValue
End Get
Set
If value <> Me.phoneNumberValue Then
Me.phoneNumberValue = value
NotifyPropertyChanged("PhoneNumber")
End If
End Set
End Property
End Class
// This class implements a simple customer type
// that implements the IPropertyChange interface.
public class DemoCustomer : INotifyPropertyChanged
{
// These fields hold the values for the public properties.
private Guid idValue = Guid.NewGuid();
private string customerName = String.Empty;
private string companyNameValue = String.Empty;
private string phoneNumberValue = String.Empty;
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
// The constructor is private to enforce the factory pattern.
private DemoCustomer()
{
customerName = "no data";
companyNameValue = "no data";
phoneNumberValue = "no data";
}
// This is the public factory method.
public static DemoCustomer CreateNewCustomer()
{
return new DemoCustomer();
}
// This property represents an ID, suitable
// for use as a primary key in a database.
public Guid ID
{
get
{
return this.idValue;
}
}
public string CompanyName
{
get {return this.companyNameValue;}
set
{
if (value != this.companyNameValue)
{
this.companyNameValue = value;
NotifyPropertyChanged("CompanyName");
}
}
}
public string PhoneNumber
{
get { return this.phoneNumberValue; }
set
{
if (value != this.phoneNumberValue)
{
this.phoneNumberValue = value;
NotifyPropertyChanged("PhoneNumber");
}
}
}
}
Compilazione del codice
Per compilare l'esempio di codice precedente:
- Incollare il codice in un file di codice vuoto. Utilizzare l'oggetto business in un'applicazione Windows Form contenente un metodo Main.
Vedere anche
Attività
Procedura: applicare il modello PropertyNameChanged
Concetti
Notifica delle modifiche nell'associazione dati dei Windows Form