C# GetResponse抛出WebException和ex。响应为null

我发现了如何在GetResponse调用中处理WebException的示例，并对如何从WebException响应中提取响应感到困惑。第二个难题是为什么空响应被视为抛出；有什么建议吗

HttpWebResponse response = null;
try
{
    response = (HttpWebResponse) request.GetResponse();
}
catch (WebException ex)
{
    response = (HttpWebResponse)ex.Response;
    if (null == response)
    {
        throw;
    }
}

---

响应永远不应该是

null

——在这种情况下，作者说

WebException

不能在此异常处理程序中处理，它只是向上传播

但这种异常处理并不理想-您可能想知道发生异常的原因，即：

catch (WebException ex)
{
    if (ex.Status == WebExceptionStatus.ProtocolError && ex.Response != null)
    {
        var resp = (HttpWebResponse)ex.Response;
        if (resp.StatusCode == HttpStatusCode.NotFound) // HTTP 404
        {
            //file not found, consider handled
            return false;
        }
    }
    //throw any other exception - this should not occur
    throw;
}