WebException 构造函数

定义

命名空间:

System.Net

程序集:

netstandard.dll, System.Net.Requests.dll

初始化 WebException 类的新实例。

重载

名称	说明
WebException()	初始化 WebException 类的新实例。
WebException(String)	使用指定的错误消息初始化类的新实例 WebException 。
WebException(SerializationInfo, StreamingContext)	已过时. 从指定SerializationInfo实例和StreamingContext实例初始化类的新实例WebException。
WebException(String, WebExceptionStatus)	使用指定的错误消息和状态初始化类的新实例 WebException 。
WebException(String, Exception)	使用指定的错误消息和嵌套异常初始化类的新实例 WebException 。
WebException(String, Exception, WebExceptionStatus, WebResponse)	使用指定的错误消息、嵌套异常、状态和响应初始化类的新实例 WebException 。

WebException()

Source:

WebException.cs

初始化 WebException 类的新实例。

public:
 WebException();

public WebException();

Public Sub New ()

示例

以下示例引发默认值 WebException。

 try   
 {
     // A 'Socket' object has been created.
     Socket httpSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

     // The IPaddress of the unknown uri is resolved using the 'Dns.Resolve' method. 
     
     IPHostEntry hostEntry = Dns.Resolve("http://www.contoso.com");

     IPAddress serverAddress = hostEntry.AddressList[0];
     IPEndPoint endPoint = new IPEndPoint(serverAddress, 80);
     httpSocket.Connect(endPoint);
     Console.WriteLine("Connection created successfully");
     httpSocket.Close();
  }
catch(SocketException e)
  {
  String exp = e.Message;	
  // Throw the WebException with no parameters.
     throw new WebException();
  }

Try
    ' A 'Socket' object has been created.
    Dim httpSocket As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
    
    ' The IPaddress of the unknown uri is resolved using the 'Dns.Resolve' method. 
     ' which leads to the 'SocketException' exception. 
    
    Dim hostEntry As IPHostEntry = Dns.Resolve("http://www.contoso.com")
    
    Dim serverAddress As IPAddress = hostEntry.AddressList(0)
    Dim endPoint As New IPEndPoint(serverAddress, 80)
    httpSocket.Connect(endPoint)
    Console.WriteLine("Connection created successfully")
    httpSocket.Close()
Catch e As SocketException
    Dim exp As [String] = e.Message
    ' Throw the WebException with no parameters.
    Throw New WebException()
End Try

注解

无参数构造函数初始化类的新实例 WebException 。 该 Message 属性初始化为描述错误的系统提供的消息。 此消息将考虑当前系统区域性。 Response属性InnerException初始化为 null. 将 Status 属性初始化为 RequestCanceled。

WebException(String)

Source:

WebException.cs

使用指定的错误消息初始化类的新实例 WebException 。

public:
 WebException(System::String ^ message);

public WebException(string? message);

new System.Net.WebException : string -> System.Net.WebException

Public Sub New (message As String)

参数

message

String

错误消息的文本。

示例

以下示例通过指定错误消息引发 WebException 该错误。

 try
{
     // A 'Socket' object has been created.
     Socket httpSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

     // The IPaddress of the unknown uri is resolved using the 'Dns.Resolve' method. 
     IPHostEntry hostEntry = Dns.Resolve(connectUri);

     IPAddress serverAddress = hostEntry.AddressList[0];
     IPEndPoint endPoint = new IPEndPoint(serverAddress, 80);
     httpSocket.Connect(endPoint);
     Console.WriteLine("Connection created successfully");
     httpSocket.Close();
  }
catch(SocketException e)
  {		     
     Console.WriteLine("\nException thrown.\nThe Original Message is: "+e.Message);
     // Throw the 'WebException' object with a message string specific to the situation.
     throw new WebException("Unable to locate the Server with 'www.contoso.com' Uri.");
  }

Try
    ' A 'Socket' object has been created.
    Dim httpSocket As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
    
    ' The IPaddress of the unknown uri is resolved using the 'Dns.Resolve' method. 
     
    Dim hostEntry As IPHostEntry = Dns.Resolve(connectUri)
    
    Dim serverAddress As IPAddress = hostEntry.AddressList(0)
    Dim endPoint As New IPEndPoint(serverAddress, 80)
    httpSocket.Connect(endPoint)
    Console.WriteLine("Connection created successfully")
    httpSocket.Close()
Catch e As SocketException
    Console.WriteLine((ControlChars.Cr + "Exception thrown." + ControlChars.Cr + "The Original Message is: " + e.Message))
    ' Throw the 'WebException' object with a message string specific to the situation.
    Throw New WebException("Unable to locate the Server with 'www.contoso.com' Uri.")
End Try

注解

实例初始化时，Message属性WebException设置为值 message。 如果是message，则属性Message将初始化为系统提供null的消息。 Response属性InnerException初始化为 null. 将 Status 属性初始化为 RequestCanceled。

另请参阅

• Exception

WebException(SerializationInfo, StreamingContext)

Source:

WebException.cs

注意

This API supports obsolete formatter-based serialization. It should not be called or extended by application code.

从指定SerializationInfo实例和StreamingContext实例初始化类的新实例WebException。

protected:
 WebException(System::Runtime::Serialization::SerializationInfo ^ serializationInfo, System::Runtime::Serialization::StreamingContext streamingContext);

[System.Obsolete("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId="SYSLIB0051", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
protected WebException(System.Runtime.Serialization.SerializationInfo serializationInfo, System.Runtime.Serialization.StreamingContext streamingContext);

[<System.Obsolete("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId="SYSLIB0051", UrlFormat="https://aka.ms/dotnet-warnings/{0}")>]
new System.Net.WebException : System.Runtime.Serialization.SerializationInfo * System.Runtime.Serialization.StreamingContext -> System.Net.WebException

Protected Sub New (serializationInfo As SerializationInfo, streamingContext As StreamingContext)

参数

serializationInfo

SerializationInfo

一个 SerializationInfo 包含序列化新 WebException项所需的信息。

streamingContext

StreamingContext

一个 StreamingContext 包含与新 WebException流关联的序列化流的源。

属性

ObsoleteAttribute

注解

此构造函数实现 ISerializable 类的 WebException 接口。

另请参阅

• ISerializable

WebException(String, WebExceptionStatus)

Source:

WebException.cs

使用指定的错误消息和状态初始化类的新实例 WebException 。

public:
 WebException(System::String ^ message, System::Net::WebExceptionStatus status);

public WebException(string? message, System.Net.WebExceptionStatus status);

new System.Net.WebException : string * System.Net.WebExceptionStatus -> System.Net.WebException

Public Sub New (message As String, status As WebExceptionStatus)

参数

message

String

错误消息的文本。

status

WebExceptionStatus

其中一个 WebExceptionStatus 值。

示例

以下示例 WebException 通过指定错误消息和一个 WebExceptionStatus.

 try
{
       // A 'Socket' object has been created.
       Socket httpSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

      // The IPaddress of the unknown uri is resolved using the 'Dns.Resolve' method. 
  
      IPHostEntry hostEntry = Dns.Resolve("http://www.contoso.com");

      IPAddress serverAddress = hostEntry.AddressList[0];
      IPEndPoint endPoint = new IPEndPoint(serverAddress, 80);
      httpSocket.Connect(endPoint);
      Console.WriteLine("Connection created successfully");
      httpSocket.Close();
   }
catch(SocketException e)
  {
      Console.WriteLine("\nException thrown.\nThe Original Message is: "+e.Message);
      // Throw the 'WebException' object with a message string and message status specific to the situation.
      throw new WebException("Unable to locate the Server with 'www.contoso.com' Uri.",WebExceptionStatus.NameResolutionFailure);
  }

Try
    ' A 'Socket' object has been created.
    Dim httpSocket As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
    
    ' The IPaddress of the unknown uri is resolved using the 'Dns.Resolve' method. 
     
    Dim hostEntry As IPHostEntry = Dns.Resolve(connectUri)
    
    Dim serverAddress As IPAddress = hostEntry.AddressList(0)
    Dim endPoint As New IPEndPoint(serverAddress, 80)
    httpSocket.Connect(endPoint)
    Console.WriteLine("Connection created successfully")
    httpSocket.Close()
Catch e As SocketException
    Console.WriteLine((ControlChars.Cr + "Exception thrown." + ControlChars.Cr + "The Original Message is: " + e.Message))
    ' Throw the 'WebException' object with a message string and message status specific to the situation.
    Throw New WebException("Unable to locate the Server with 'www.contoso.com' Uri.", WebExceptionStatus.NameResolutionFailure)
End Try

注解

实例初始化时，将WebException属性设置为值message，并将Status属性设置为值 status。Message 如果是message，则属性Message将初始化为系统提供null的消息。 Response属性InnerException初始化为 null.

WebException(String, Exception)

Source:

WebException.cs

使用指定的错误消息和嵌套异常初始化类的新实例 WebException 。

public:
 WebException(System::String ^ message, Exception ^ innerException);

public WebException(string? message, Exception? innerException);

new System.Net.WebException : string * Exception -> System.Net.WebException

Public Sub New (message As String, innerException As Exception)

参数

message

String

错误消息的文本。

innerException

Exception

嵌套异常。

示例

以下示例通过指定错误消息和嵌套异常引发 WebException 异常。

   try
   {
          // A 'Socket' object has been created.
          Socket httpSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

          // The IPaddress of the unknown uri is resolved using the 'Dns.Resolve' method. 
       
          IPHostEntry hostEntry = Dns.Resolve(connectUri);

          IPAddress serverAddress = hostEntry.AddressList[0];
          IPEndPoint endPoint = new IPEndPoint(serverAddress, 80);
          httpSocket.Connect(endPoint);
          Console.WriteLine("Connection created successfully");
          httpSocket.Close();		 
    }
  catch(SocketException e)
{ 
       Console.WriteLine("\nException thrown.\nThe Original Message is: "+e.Message);
       //  Throw the 'WebException' object with a message string specific to the situation; 
          //  and the 'InnerException' which actually lead to this exception.
          throw new WebException("Unable to locate the Server with 'www.contoso.com' Uri.",e);
    }

Try
    ' A 'Socket' object has been created.
    Dim httpSocket As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
    
    ' The IPaddress of the unknown uri is resolved using the 'Dns.Resolve' method. 
     Dim hostEntry As IPHostEntry = Dns.Resolve(connectUri)
    
    Dim serverAddress As IPAddress = hostEntry.AddressList(0)
    Dim endPoint As New IPEndPoint(serverAddress, 80)
    httpSocket.Connect(endPoint)
    Console.WriteLine("Connection created successfully")
    httpSocket.Close()
Catch e As SocketException
    Console.WriteLine((ControlChars.Cr + "Exception thrown." + ControlChars.Cr + "The Original Message is: " + e.Message))
    ' Throw the 'WebException' object with a message string specific to the situation. 
     ' and the 'InnerException' which actually lead to this exception.
    Throw New WebException("Unable to locate the Server with 'www.contoso.com' Uri.", e)
End Try

注解

实例初始化时，将WebException属性设置为值message，并将InnerException属性设置为值 innerException。Message 如果是message，则属性Message将初始化为系统提供null的消息。 Response属性InnerException初始化为 null. 将 Status 属性初始化为 RequestCanceled。

另请参阅

• Exception

WebException(String, Exception, WebExceptionStatus, WebResponse)

Source:

WebException.cs

使用指定的错误消息、嵌套异常、状态和响应初始化类的新实例 WebException 。

public:
 WebException(System::String ^ message, Exception ^ innerException, System::Net::WebExceptionStatus status, System::Net::WebResponse ^ response);

public WebException(string? message, Exception? innerException, System.Net.WebExceptionStatus status, System.Net.WebResponse? response);

new System.Net.WebException : string * Exception * System.Net.WebExceptionStatus * System.Net.WebResponse -> System.Net.WebException

Public Sub New (message As String, innerException As Exception, status As WebExceptionStatus, response As WebResponse)

参数

message

String

错误消息的文本。

innerException

Exception

嵌套异常。

status

WebExceptionStatus

其中一个 WebExceptionStatus 值。

response

WebResponse

包含 WebResponse 来自远程主机的响应的实例。

示例

以下示例 WebException 通过指定错误消息和一个 WebExceptionStatus.

      // Send the data. 
      Encoding ASCII = Encoding.ASCII;
      string requestPage = "GET /nhjj.htm HTTP/1.1\r\nHost: " + connectUri + "\r\nConnection: Close\r\n\r\n";
      Byte[] byteGet = ASCII.GetBytes(requestPage);
      Byte[] recvBytes = new Byte[256];

      // Create an 'IPEndPoint' object.
 
      IPHostEntry hostEntry = Dns.Resolve(connectUri);
      IPAddress serverAddress = hostEntry.AddressList[0];
      IPEndPoint endPoint = new IPEndPoint(serverAddress, 80);

      // Create a 'Socket' object  for sending data.
      Socket connectSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream,ProtocolType.Tcp);
 
      // Connect to host using 'IPEndPoint' object.

      connectSocket.Connect(endPoint);
 
      // Sent the 'requestPage' text to the host.
      connectSocket.Send(byteGet, byteGet.Length, 0);
 
      // Receive the information sent by the server.
      Int32 bytesReceived = connectSocket.Receive(recvBytes, recvBytes.Length, 0);
      String headerString = ASCII.GetString(recvBytes, 0, bytesReceived);

     // Check whether 'status 404' is there or not in the information sent by server.
     if(headerString.IndexOf("404")!=-1)
     {	 
         bytesReceived = connectSocket.Receive(recvBytes, recvBytes.Length, 0);
         MemoryStream memoryStream = new MemoryStream(recvBytes);
         getStream = (Stream) memoryStream;
 
         // Create a 'WebResponse' object
         WebResponse myWebResponse = (WebResponse) new HttpConnect(getStream);
         Exception myException = new Exception("File Not found");

         // Throw the 'WebException' object with a message string, message status,InnerException and WebResponse
         throw new WebException("The Requested page is not found.",myException,WebExceptionStatus.ProtocolError,myWebResponse);
     }

     connectSocket.Close();

     ' Send the data. 
       Dim ASCII As Encoding = Encoding.ASCII
       Dim requestPage As String = "GET /nhjj.htm HTTP/1.1" + ControlChars.Lf + ControlChars.Cr + "Host: " + connectUri + ControlChars.Lf + ControlChars.Cr + "Connection: Close" + ControlChars.Lf + ControlChars.Cr + ControlChars.Lf + ControlChars.Cr
       Dim byteGet As [Byte]() = ASCII.GetBytes(requestPage)
       Dim recvBytes(256) As [Byte]
       
       ' Create an 'IPEndPoint' object.
       Dim hostEntry As IPHostEntry = Dns.Resolve(connectUri)
       Dim serverAddress As IPAddress = hostEntry.AddressList(0)
       Dim endPoint As New IPEndPoint(serverAddress, 80)
       
       ' Create a 'Socket' object  for sending data.
       Dim connectSocket As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
       
       ' Connect to host using 'IPEndPoint' object.
       connectSocket.Connect(endPoint)
       
       ' Sent the 'requestPage' text to the host.
       connectSocket.Send(byteGet, byteGet.Length, 0)
       
       ' Receive the information sent by the server.
       Dim bytesReceived As Int32 = connectSocket.Receive(recvBytes, recvBytes.Length, 0)
       Dim headerString As [String] = ASCII.GetString(recvBytes, 0, bytesReceived)
      
       ' Check whether 'status 404' is there or not in the information sent by server.
       If headerString.IndexOf("404") <> False Then
           bytesReceived = connectSocket.Receive(recvBytes, recvBytes.Length, 0)
           Dim memoryStream As New MemoryStream(recvBytes)
           getStream = CType(memoryStream, Stream)
           
           ' Create a 'WebResponse' object.
           Dim myWebResponse As WebResponse = CType(New HttpConnect(getStream), WebResponse)
           Dim myException As New Exception("File Not found")
           
           ' Throw the 'WebException' object with a message string, message status,InnerException and WebResponse.
           Throw New WebException("The Requested page is not found.", myException, WebExceptionStatus.ProtocolError, myWebResponse)
       End If 

       connectSocket.Close()

注解

实例初始化时，该WebException属性设置为值，InnerException属性设置为值message，Status属性设置为值statusinnerException，属性Response设置为值。属性设置为值response。Message 如果是message，则属性Message将初始化为系统提供null的消息。