WebClient WebClient WebClient Constructor

Definizione

Inizializza una nuova istanza della classe WebClient.Initializes a new instance of the WebClient class.

public:
 WebClient();
public WebClient ();
Public Sub New ()

Esempi

L'esempio di codice seguente crea un WebClient dell'istanza e lo usa per scaricare i dati da un server e visualizzarlo sulla console di sistema, per scaricare i dati da un server e scriverli in un file e per caricare i valori del form in un server e ricevere la risposta.The following code example creates a WebClient instance and then uses it to download data from a server and display it on the system console, to download data from a server and write it to a file, and to upload form values to a server and receive the response.

try
{
   // Download the data to a buffer.
   WebClient^ client = gcnew WebClient;

   array<Byte>^ pageData = client->DownloadData( "http://www.contoso.com" );
   String^ pageHtml = Encoding::ASCII->GetString( pageData );
   Console::WriteLine( pageHtml );
   
   // Download the data to a file.
   client->DownloadFile( "http://www.contoso.com", "page.htm" );
   
   // Upload some form post values.
   NameValueCollection^ form = gcnew NameValueCollection;
   form->Add( "MyName", "MyValue" );
   array<Byte>^ responseData = client->UploadValues( "http://www.contoso.com/form.aspx", form );
}
catch ( WebException^ webEx ) 
{
   Console::WriteLine( webEx->ToString() );
   if ( webEx->Status == WebExceptionStatus::ConnectFailure )
   {
      Console::WriteLine( "Are you behind a firewall?  If so, go through the proxy server." );
   }
}
      try {
	
// Download the data to a buffer.
      	WebClient client = new WebClient();

		Byte[] pageData = client.DownloadData("http://www.contoso.com");
string pageHtml = Encoding.ASCII.GetString(pageData);
Console.WriteLine(pageHtml);

// Download the data to a file.
       	client.DownloadFile("http://www.contoso.com", "page.htm");

// Upload some form post values.
NameValueCollection form = new NameValueCollection();		
form.Add("MyName", "MyValue");		
Byte[] responseData = client.UploadValues("http://www.contoso.com/form.aspx", form);		

      }
      catch (WebException webEx) {
        	Console.WriteLine(webEx.ToString());
         	if(webEx.Status == WebExceptionStatus.ConnectFailure) {
         		Console.WriteLine("Are you behind a firewall?  If so, go through the proxy server.");
         	}
      }
Public Shared Sub Main()


    Try
        Dim client As New WebClient()
        Dim pageData As [Byte]() = client.DownloadData("http://www.contoso.com")
        Dim pageHtml As String = Encoding.ASCII.GetString(pageData)

        ' Download the data to a buffer.
        Console.WriteLine(pageHtml)
        
        ' Download the data to a file.
        client.DownloadFile("http://www.contoso.com", "page.htm")
        
        
        ' Upload some form post values.
        dim form as New NameValueCollection()
  form.Add("MyName", "MyValue")  

  ' Note that you need to replace "http://localhost/somefile.aspx" with the name of 
  ' a file that is available to your computer.
  Dim responseData As [Byte]() = client.UploadValues("http://www.contoso.com/form.aspx", form)      
        Console.WriteLine(Encoding.ASCII.GetString(responseData))
    
    Catch webEx As WebException
        if webEx.Status = WebExceptionStatus.ConnectFailure then
           Console.WriteLine("Are you behind a firewall?  If so, go through the proxy server.")
        end if
        Console.Write(webEx.ToString())
    End Try
    

End Sub 'Main

Commenti

Il costruttore predefinito crea una nuova istanza di WebClient classe.The default constructor creates a new instance of the WebClient class. Il metodo HTTP predefinito è GET.The default HTTP method is GET. Il metodo FTP predefinito è RETR.The default FTP method is RETR. Il valore predefinito di Encoding è Default.The default Encoding is Default. Il valore predefinito di AllowAutoRedirect è true.The default value of AllowAutoRedirect is true.

Si applica a