WebClient.Headers 属性

public:
 property System::Net::WebHeaderCollection ^ Headers { System::Net::WebHeaderCollection ^ get(); void set(System::Net::WebHeaderCollection ^ value); };

public System.Net.WebHeaderCollection Headers { get; set; }

member this.Headers : System.Net.WebHeaderCollection with get, set

Public Property Headers As WebHeaderCollection

属性值

包含与此请求关联的标头名称/值对的 WebHeaderCollection。

示例

下面的代码示例使用 Headers 集合将 HTTP Content-Type 标头设置为 application/x-www-form-urlencoded,，以通知服务器表单数据已附加到帖子。

String^ uriString;
Console::Write( "\nPlease enter the URI to post data to {for example, http://www.contoso.com}: " );
uriString = Console::ReadLine();

// Create a new WebClient instance.
WebClient^ myWebClient = gcnew WebClient;
Console::WriteLine( "\nPlease enter the data to be posted to the URI {0}:", uriString );
String^ postData = Console::ReadLine();
myWebClient->Headers->Add( "Content-Type", "application/x-www-form-urlencoded" );

// Displays the headers in the request
Console::Write( "Resulting Request Headers: ");
Console::WriteLine(myWebClient->Headers);

// Apply ASCII Encoding to obtain the String^ as a Byte array.
array<Byte>^ byteArray = Encoding::ASCII->GetBytes( postData );
Console::WriteLine( "Uploading to {0} ...", uriString );
// Upload the input String* using the HTTP 1.0 POST method.
array<Byte>^responseArray = myWebClient->UploadData( uriString, "POST", byteArray );
// Decode and display the response.
Console::WriteLine( "\nResponse received was {0}",
   Encoding::ASCII->GetString( responseArray ) );

   string uriString;
       Console.Write("\nPlease enter the URI to post data to {for example, http://www.contoso.com} : ");
       uriString = Console.ReadLine();

       // Create a new WebClient instance.
       WebClient myWebClient = new WebClient();
       Console.WriteLine("\nPlease enter the data to be posted to the URI {0}:",uriString);
       string postData = Console.ReadLine();
       myWebClient.Headers.Add("Content-Type","application/x-www-form-urlencoded");

 // Display the headers in the request
       Console.Write("Resulting Request Headers: ");
       Console.WriteLine(myWebClient.Headers.ToString());
       
       // Apply ASCII Encoding to obtain the string as a byte array.

       byte[] byteArray = Encoding.ASCII.GetBytes(postData);
       Console.WriteLine("Uploading to {0} ...",  uriString);						
       // Upload the input string using the HTTP 1.0 POST method.
       byte[] responseArray = myWebClient.UploadData(uriString,"POST",byteArray);
       
       // Decode and display the response.
       Console.WriteLine("\nResponse received was {0}",
       Encoding.ASCII.GetString(responseArray));
                 

Dim uriString As String
Console.Write(ControlChars.Cr + "Please enter the URI to post data to{for example, http://www.contoso.com} : ")
uriString = Console.ReadLine()

' Create a new WebClient instance.
Dim myWebClient As New WebClient()
Console.WriteLine(ControlChars.Cr + "Please enter the data to be posted to the URI {0}:", uriString)
Dim postData As String = Console.ReadLine()
myWebClient.Headers.Add("Content-Type", "application/x-www-form-urlencoded")

' Display the headers in the request
Console.Write("Resulting Request Headers: ")
Console.Writeline(myWebClient.Headers.ToString())

' Apply ASCII Encoding to obtain the string as a byte array.
Dim byteArray As Byte() = Encoding.ASCII.GetBytes(postData)
Console.WriteLine("Uploading to {0} ...", uriString)
' Upload the input string using the HTTP 1.0 POST method.
Dim responseArray As Byte() = myWebClient.UploadData(uriString, "POST", byteArray)
' Decode and display the response.
Console.WriteLine(ControlChars.Cr + "Response received was :{0}", Encoding.ASCII.GetString(responseArray))

注解

Headers 属性包含一个 WebHeaderCollection 实例，该实例包含 WebClient 随请求一起发送的协议标头。

某些常见标头被视为受限，受系统保护，无法在 WebHeaderCollection 对象中设置或更改。 尝试在与 WebClient 对象关联的 WebHeaderCollection 对象中设置这些受限标头之一的任何尝试稍后都会在尝试发送 WebClient 请求时引发异常。

受系统保护的受限标头包括但不限于：

• 日期

• 主机

此外，使用 WebClient 对象时，其他一些标头也会受到限制。 这些受限标头包括但不限于以下内容：

• 接受

• 连接

• Content-Length

• 预期（如果值设置为“100-continue”

• If-Modified-Since

• 范围

• Transfer-Encoding

HttpWebRequest 类具有设置上述一些标头的属性。 如果应用程序必须设置这些标头，则应使用 HttpWebRequest 类而不是 WebRequest 类。

不应假定标头值将保持不变，因为 Web 服务器和缓存可能会更改或向 Web 请求添加标头。

另请参阅

• Headers
• Headers