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

Procedura: generare notifiche di modifica utilizzando un BindingSource e l'interfaccia INotifyPropertyChanged

Concetti

Notifica delle modifiche nell'associazione dati dei Windows Form

Altre risorse

Associazione ai dati di Windows Form