如何在 C# 中有效地检查来自 URL 的 401 响应？

发布于 2024-11-24 16:31:45 字数 635 浏览 1 评论 0原文

我想创建一个方法来确定特定 URL 是否可以匿名使用。我这样做是为了从自定义搜索页面中删除无法访问的结果。我能想到的最好的办法是

    public bool IsWebAddressAccessible(string Url)
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
        try
        {
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        }
        catch (System.Net.WebException)
        {
            return false;
        }
        return true;
    }

然而，由于两个原因，这并不理想。首先，据我了解，以这种方式依赖异常进行逻辑效率不高。其次，在页面可访问的情况下，似乎要检索整个页面，这很耗时。所以问题是：

有没有一种方法可以在不依赖异常的情况下做到这一点？
有没有办法加快速度，这样我就可以查看响应是否返回 401，而无需等待检索整个页面？

原文

I would like to create a method that determines if a particular URL is available anonymously. I'm doing this in order to strip out inaccessible results from a custom search page. The best I can come up with is

    public bool IsWebAddressAccessible(string Url)
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
        try
        {
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        }
        catch (System.Net.WebException)
        {
            return false;
        }
        return true;
    }

However, this is less than ideal for a few two reasons. Firstly, as I understand, it's not efficient to rely on exceptions for logic in this way. Secondly, in the case where the page is accessible, it seems to retrieve the whole page, which is time-consuming. So the questions are:

Is there a way to do this without relying on exceptions?
Is there a way to speed this up so I can just see whether the response is coming back as 401 or not without waiting to retrieve the entire page?

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趴在窗边数星星i 2024-12-01 16:31:45

这是一个令人烦恼的异常在HttpWebRequest的设计中。实际上，我的一个项目中有几个扩展方法（其中一个会发出大量请求，预计会返回 304 未修改）：
<前><代码>[调试器非用户代码]
公共静态 HttpWebResponse GetHttpResponse（此 HttpWebRequest 请求）{
// 我们知道响应将是 HttpWebResponse 因为请求是 HttpWebRequest
返回 (HttpWebResponse)request.GetResponse();
}
[调试器非用户代码]
公共静态 HttpWebResponse GetHttpResponseAvoidVusingExceptions（此 HttpWebRequest 请求）{
尝试 {
返回 GetHttpResponse(请求);
} catch (WebException ex) {
HttpWebResponse 响应 = (HttpWebResponse)ex.Response;
开关（响应.StatusCode）{
案例 HttpStatusCode.NotModified：
返回响应；
默认：
// 我们不捕获其他异常
扔;
}
}
}
我不知道如何避免此异常。
就像 Mark 所说，使用 HEAD 方法仅获取响应标头。

this is a vexing exception in the design of HttpWebRequest. I've actually got a couple of extension methods in one of my projects (one that makes a lot of requests that are expected to return 304 not modified):

[DebuggerNonUserCode]
public static HttpWebResponse GetHttpResponse(this HttpWebRequest request) {
    // We know the response will be a HttpWebResponse because the request is a HttpWebRequest
    return (HttpWebResponse)request.GetResponse();
}

[DebuggerNonUserCode]
public static HttpWebResponse GetHttpResponseAvoidVexingExceptions(this HttpWebRequest request) {
    try {
        return GetHttpResponse(request);
    } catch (WebException ex) {
        HttpWebResponse response = (HttpWebResponse)ex.Response;
        switch (response.StatusCode) {
            case HttpStatusCode.NotModified:
                return response;

            default:
                // We don't catch other exceptions
                throw;
        }
    }
}

There's no way I'm aware of to avoid this exception.