从相对路径获取绝对 URL(重构方法) [英] Get Absolute URL from Relative path (refactored method)

问题描述

我真的很惊讶没有本地 .NET 方法可以从相对 url 获取绝对 url.我知道这已经被讨论过很多次了，但从来没有遇到过一个令人满意的方法来处理这个问题.你能帮助微调下面的方法吗?

I am really surprised that there is no native .NET method to get an absolute url from a relative url. I know this has been discussed many times, but never have come across a satisfactory method that handles this well. Can you help fine tune the method below?

我想剩下的就是自动选择协议而不是硬编码(http/https).我还有什么遗漏(警告、性能等)?

I think all I need left is to auto choose the protocol instead of hard coding it (http/https). Anything else I am missing (caveats, performance, etc)?

public static string GetAbsoluteUrl(string url)
    {
        //VALIDATE INPUT FOR ALREADY ABSOLUTE URL
        if (url.StartsWith("http://", StringComparison.OrdinalIgnoreCase) 
           || url.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
        { 
            return url;
        }

        //GET PAGE REFERENCE FOR CONTEXT PROCESSING
        Page page = HttpContext.Current.Handler as Page;

        //RESOLVE PATH FOR APPLICATION BEFORE PROCESSING
        if (url.StartsWith("~/"))
        {
            url = page.ResolveUrl(url);
        }

        //BUILD AND RETURN ABSOLUTE URL
        return "http://" + page.Request.ServerVariables["SERVER_NAME"] + "/" 
                         + url.TrimStart('/');
    }

推荐答案

这一直是我处理这个小麻烦的方法.注意 VirtualPathUtility.ToAbsolute(relativeUrl) 允许将方法声明为静态类中的扩展.

This has always been my approach to this little nuisance. Note the use of VirtualPathUtility.ToAbsolute(relativeUrl) allows the method to be declared as an extension in a static class.

/// <summary>
/// Converts the provided app-relative path into an absolute Url containing the 
/// full host name
/// </summary>
/// <param name="relativeUrl">App-Relative path</param>
/// <returns>Provided relativeUrl parameter as fully qualified Url</returns>
/// <example>~/path/to/foo to http://www.web.com/path/to/foo</example>
public static string ToAbsoluteUrl(this string relativeUrl) {
    if (string.IsNullOrEmpty(relativeUrl))
        return relativeUrl;

    if (HttpContext.Current == null)
        return relativeUrl;

    if (relativeUrl.StartsWith("/"))
        relativeUrl = relativeUrl.Insert(0, "~");
    if (!relativeUrl.StartsWith("~/"))
        relativeUrl = relativeUrl.Insert(0, "~/");

    var url = HttpContext.Current.Request.Url;
    var port = url.Port != 80 ? (":" + url.Port) : String.Empty;

    return String.Format("{0}://{1}{2}{3}",
        url.Scheme, url.Host, port, VirtualPathUtility.ToAbsolute(relativeUrl));
}

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