WebClient Konstruktor

Definice

Obor názvů:

System.Net

Sestavení:

netstandard.dll, System.Net.WebClient.dll

Zdroj:

WebClient.cs

Upozornění

WebRequest, HttpWebRequest, ServicePoint, and WebClient are obsolete. Use HttpClient instead.

Inicializuje novou instanci WebClient třídy.

public:
 WebClient();

[System.Obsolete("WebRequest, HttpWebRequest, ServicePoint, and WebClient are obsolete. Use HttpClient instead.", DiagnosticId="SYSLIB0014", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
public WebClient();

Public Sub New ()

Atributy

ObsoleteAttribute

Příklady

Následující příklad kódu vytvoří WebClient instanci a pak ji použije ke stažení dat ze serveru a jeho zobrazení v systémové konzole, ke stažení dat ze serveru a zápisu do souboru a k nahrání hodnot formulářů na server a přijetí odpovědi.

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

Poznámky

Konstruktor bez parametrů vytvoří novou instanci WebClient třídy. Výchozí metoda HTTP je GET. Výchozí metoda FTP je RETR. Výchozí hodnota Encoding je Default. Výchozí hodnota atributu AllowAutoRedirect je true.