WebClient.DownloadStringCompleted 事件

定義

命名空間:

System.Net

組件:

System.Net.WebClient.dll

來源:

WebClient.cs

發生於異步資源下載作業完成時。

public:
 event System::Net::DownloadStringCompletedEventHandler ^ DownloadStringCompleted;

public event System.Net.DownloadStringCompletedEventHandler? DownloadStringCompleted;

member this.DownloadStringCompleted : System.Net.DownloadStringCompletedEventHandler 

Public Custom Event DownloadStringCompleted As DownloadStringCompletedEventHandler 

事件類型

DownloadStringCompletedEventHandler

範例

下列程式代碼範例示範如何設定此事件的事件處理程式。

// Sample call : DownloadStringInBackground2 ("http://www.contoso.com/GameScores.html");
void DownloadStringInBackground2( String^ address )
{
   WebClient^ client = gcnew WebClient;
   Uri ^uri = gcnew Uri(address);

   // Specify that the DownloadStringCallback2 method gets called
   // when the download completes.
   client->DownloadStringCompleted += gcnew DownloadStringCompletedEventHandler( DownloadStringCallback2 );
   client->DownloadStringAsync( uri );
}

// Sample call : DownloadStringInBackground2 ("http://www.contoso.com/GameScores.html");
public static void DownloadStringInBackground2(string address)
{
    WebClient client = new WebClient();
    Uri uri = new Uri(address);

    // Specify that the DownloadStringCallback2 method gets called
    // when the download completes.
    client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(DownloadStringCallback2);
    client.DownloadStringAsync(uri);
}

'  Sample call : DownloadStringInBackground2 ("http:' www.contoso.com/GameScores.html")
Public Shared Sub DownloadStringInBackground2(ByVal address As String)

    Dim client As WebClient = New WebClient()

    '  Specify that the DownloadStringCallback2 method gets called
    '  when the download completes.
    AddHandler client.DownloadStringCompleted, AddressOf DownloadStringCallback2
                Dim uri as Uri = New Uri(address)
    client.DownloadStringAsync(uri)
End Sub

下列程式代碼範例示範此事件的處理程序實作。

void DownloadStringCallback2( Object^ /*sender*/, DownloadStringCompletedEventArgs^ e )
{

   // If the request was not canceled and did not throw
   // an exception, display the resource.
   if (  !e->Cancelled && e->Error == nullptr )
   {
      String^ textString = dynamic_cast<String^>(e->Result);
      Console::WriteLine( textString );
   }
}

private static void DownloadStringCallback2(Object sender, DownloadStringCompletedEventArgs e)
{
    // If the request was not canceled and did not throw
    // an exception, display the resource.
    if (!e.Cancelled && e.Error == null)
    {
        string textString = (string)e.Result;

        Console.WriteLine(textString);
    }
}

Private Shared Sub DownloadStringCallback2(ByVal sender As Object, ByVal e As DownloadStringCompletedEventArgs)

    '  If the request was not canceled and did not throw
    '  an exception, display the resource.
    If e.Cancelled = False AndAlso e.Error Is Nothing Then

        Dim textString As String = CStr(e.Result)
        Console.WriteLine(textString)
    End If
End Sub

備註

謹慎

WebRequest、HttpWebRequest、ServicePoint和 WebClient 已經過時，您不應該將它們用於新的開發。 請改用 HttpClient。

每次異步操作以字串完成下載資源時，都會引發此事件。 這些作業會藉由呼叫 DownloadStringAsync 方法啟動。

DownloadStringCompletedEventHandler 是這個事件的委派。 DownloadStringCompletedEventArgs 類別會提供事件處理程式與事件數據。

如需如何處理事件的詳細資訊，請參閱 處理和引發事件。