Question

我有以下代码：

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "HEAD";
request.Credentials = MyCredentialCache;

try
{
    request.GetResponse();
}
catch
{
}

如何捕获特定的404错误？ WebExceptionStatus.ProtocolError只能检测到发生了错误，但没有提供错误的确切代码。

例如：

catch (WebException ex)
{
    if (ex.Status != WebExceptionStatus.ProtocolError)
    {
        throw ex;
    }
}

仅仅是没用的......协议异常可能是401,503,403，真的。

Answer 1

try
{
    var request = WebRequest.Create(uri);
    using (var response = request.GetResponse())
    {
        using (var responseStream = response.GetResponseStream())
        {
            // Process the stream
        }
    }
}
catch (WebException ex)
{
    if (ex.Status == WebExceptionStatus.ProtocolError &&
        ex.Response != null)
    {
        var resp = (HttpWebResponse) ex.Response;
        if (resp.StatusCode == HttpStatusCode.NotFound)
        {
            // Do something
        }
        else
        {
            // Do something else
        }
    }
    else
    {
        // Do something else
    }
}

Answer 2

使用HttpStatusCode Enumeration，特别是HttpStatusCode.NotFound

类似的东西：

HttpWebResponse errorResponse = we.Response as HttpWebResponse;
if (errorResponse.StatusCode == HttpStatusCode.NotFound) {
  //
}

其中
we是WebException。

Answer 3

在C＃6中，您可以使用exception filters。

try
{
    var request = WebRequest.Create(uri);
    using (var response = request.GetResponse())
    using (var responseStream = response.GetResponseStream())
    {
        // Process the stream
    }
}
catch(WebException ex) when ((ex.Response as HttpWebResponse)?.StatusCode == HttpStatusCode.NotFound)
{
    // handle 404 exceptions
}
catch (WebException ex)
{
    // handle other web exceptions
}

Answer 4

我没有对此进行测试，但它应该可以正常运行

try
{
    // TODO: Make request.
}
catch (WebException ex)
{
    if (ex.Status == WebExceptionStatus.ProtocolError) {
        HttpWebResponse resp = ex.Response as HttpWebResponse;
        if (resp != null && resp.StatusCode == HttpStatusCode.NotFound)
        {
            // TODO: Handle 404 error.
        }
        else
            throw;
    }
    else
        throw;
}

Answer 5

我想如果你抓到WebException，那里有一些信息你可以用来确定它是否是404.这是我目前唯一知道的方式......我会感兴趣知道任何其他人......

catch(WebException e) {
    if(e.Status == WebExceptionStatus.ProtocolError) {
        var statusCode = (HttpWebResponse)e.Response).StatusCode);
        var description = (HttpWebResponse)e.Response).StatusDescription);
    }
}

Answer 6

查看此片段。 GetResponse将抛出WebRequestException。抓住它，你就可以从响应中获取状态代码。

try {
   // Create a web request for an invalid site. Substitute the "invalid site" strong in the Create call with a invalid name.
     HttpWebRequest myHttpWebRequest = (HttpWebRequest) WebRequest.Create("invalid site");

    // Get the associated response for the above request.
     HttpWebResponse myHttpWebResponse = (HttpWebResponse) myHttpWebRequest.GetResponse();
    myHttpWebResponse.Close();
}
catch(WebException e) {
    Console.WriteLine("This program is expected to throw WebException on successful run."+
                        "\n\nException Message :" + e.Message);
    if(e.Status == WebExceptionStatus.ProtocolError) {
        Console.WriteLine("Status Code : {0}", ((HttpWebResponse)e.Response).StatusCode);
        Console.WriteLine("Status Description : {0}", ((HttpWebResponse)e.Response).StatusDescription);
    }
}
catch(Exception e) {
    Console.WriteLine(e.Message);
}

这来自http://msdn.microsoft.com/en-us/library/system.net.webexception.status.aspx

Answer 7

请参阅MSDN有关回复状态的信息：

...
catch(WebException e) {
  Console.WriteLine("The following error occured : {0}",e.Status);  
}
...

Answer 8

对于浏览这个的VB.NET人员，我相信只有当它真的是404时我们才能捕获异常。例如：

Try
    httpWebrequest.GetResponse()
Catch we As WebException When we.Response IsNot Nothing _
                              AndAlso TypeOf we.Response Is HttpWebResponse _
                              AndAlso (DirectCast(we.Response, HttpWebResponse).StatusCode = HttpStatusCode.NotFound)

    ' ...

End Try

Answer 9

抓住正确的异常类型WebException：

try
{
    var request = (HttpWebRequest) WebRequest.Create(String.Format("http://www.gravatar.com/avatar/{0}?d=404", hashe));

    using(var response = (HttpWebResponse)request.GetResponse())
        Response.Write("has avatar");
}
catch(WebException e) 
{
  if(e.Response.StatusCode == 404) 
    Response.Write("No avatar");
}

Answer 10

当使用WebRequest类将POST或GET数据发送到服务器时，异常的类型将是WebException.Below是文件未找到异常的代码

/// <reference path="./path/to/downloaded/xregexp.d.ts" />

我怎么能抓到404？

10 个答案: