OpenReadCompletedEventHandler Delegar

Definição

public delegate void OpenReadCompletedEventHandler(System::Object ^ sender, OpenReadCompletedEventArgs ^ e);

public delegate void OpenReadCompletedEventHandler(object sender, OpenReadCompletedEventArgs e);

type OpenReadCompletedEventHandler = delegate of obj * OpenReadCompletedEventArgs -> unit

Public Delegate Sub OpenReadCompletedEventHandler(sender As Object, e As OpenReadCompletedEventArgs)

Parâmetros

Exemplos

O seguinte exemplo de código demonstra como descarregar um recurso para leitura.

public static void OpenResourceForReading2(string address)
{
    WebClient client = new WebClient();
    Uri uri = new Uri(address);

    client.OpenReadCompleted += new OpenReadCompletedEventHandler(OpenReadCallback2);
    client.OpenReadAsync(uri);
}

Public Shared Sub OpenResourceForReading2(ByVal address As String)

    Dim client As WebClient = New WebClient()
    AddHandler client.OpenReadCompleted, AddressOf OpenReadCallback2
                Dim uri as Uri = New Uri(address)
    client.OpenReadAsync(uri)
End Sub

O seguinte método é chamado quando o download termina.

private static void OpenReadCallback2(Object sender, OpenReadCompletedEventArgs e)
{
    Stream reply = null;
    StreamReader s = null;

    try
    {
        reply = (Stream)e.Result;
        s = new StreamReader(reply);
        Console.WriteLine(s.ReadToEnd());
    }
    finally
    {
        if (s != null)
        {
            s.Close();
        }

        if (reply != null)
        {
            reply.Close();
        }
    }
}

Private Shared Sub OpenReadCallback2(ByVal sender As Object, ByVal e As OpenReadCompletedEventArgs)

    Dim reply As Stream = Nothing
    Dim s As StreamReader = Nothing

    Try

        reply = CType(e.Result, Stream)
        s = New StreamReader(reply)
        Console.WriteLine(s.ReadToEnd())
    Finally

        If Not s Is Nothing Then

            s.Close()
        End If

        If Not reply Is Nothing Then

            reply.Close()
        End If
    End Try
End Sub

Observações

Quando cria um OpenReadCompletedEventHandler delegado, identifica o método que irá gerir o evento. Para associar o evento ao seu gestor de eventos, adicione uma instância do delegado ao evento. O gestor de eventos é chamado sempre que o evento ocorre, a menos que remova o delegado.