Path.Combine很方便,但是.NET框架中是否有类似的URL函数?

我正在寻找这样的语法:

Url.Combine("http://MyUrl.com/", "/Images/Image.jpg")

这将返回:

"http://MyUrl.com/Images/Image.jpg"


当前回答

Ryan Cook的答案与我的目标接近,可能更适合其他开发人员。然而,它在字符串的开头添加了http://,并且一般来说,它的格式比我想要的要多一些。

此外,对于我的用例,解析相对路径并不重要。

mdsharp的答案也包含了一个好主意的种子,尽管实际实现需要更多细节才能完成。这是一种充实它的尝试(我在生产中使用了这一点):

C#

public string UrlCombine(string url1, string url2)
{
    if (url1.Length == 0) {
        return url2;
    }

    if (url2.Length == 0) {
        return url1;
    }

    url1 = url1.TrimEnd('/', '\\');
    url2 = url2.TrimStart('/', '\\');

    return string.Format("{0}/{1}", url1, url2);
}

VB.NET

Public Function UrlCombine(ByVal url1 As String, ByVal url2 As String) As String
    If url1.Length = 0 Then
        Return url2
    End If

    If url2.Length = 0 Then
        Return url1
    End If

    url1 = url1.TrimEnd("/"c, "\"c)
    url2 = url2.TrimStart("/"c, "\"c)

    Return String.Format("{0}/{1}", url1, url2)
End Function

这段代码通过了以下测试,恰好是在VB中:

<TestMethod()> Public Sub UrlCombineTest()
    Dim target As StringHelpers = New StringHelpers()

    Assert.IsTrue(target.UrlCombine("test1", "test2") = "test1/test2")
    Assert.IsTrue(target.UrlCombine("test1/", "test2") = "test1/test2")
    Assert.IsTrue(target.UrlCombine("test1", "/test2") = "test1/test2")
    Assert.IsTrue(target.UrlCombine("test1/", "/test2") = "test1/test2")
    Assert.IsTrue(target.UrlCombine("/test1/", "/test2/") = "/test1/test2/")
    Assert.IsTrue(target.UrlCombine("", "/test2/") = "/test2/")
    Assert.IsTrue(target.UrlCombine("/test1/", "") = "/test1/")
End Sub

其他回答

我的通用解决方案:

public static string Combine(params string[] uriParts)
{
    string uri = string.Empty;
    if (uriParts != null && uriParts.Any())
    {
        char[] trims = new char[] { '\\', '/' };
        uri = (uriParts[0] ?? string.Empty).TrimEnd(trims);

        for (int i = 1; i < uriParts.Length; i++)
        {
            uri = string.Format("{0}/{1}", uri.TrimEnd(trims), (uriParts[i] ?? string.Empty).TrimStart(trims));
        }
    }

    return uri;
}

我结合了前面的所有答案:

    public static string UrlPathCombine(string path1, string path2)
    {
        path1 = path1.TrimEnd('/') + "/";
        path2 = path2.TrimStart('/');

        return Path.Combine(path1, path2)
            .Replace(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
    }

    [TestMethod]
    public void TestUrl()
    {
        const string P1 = "http://msdn.microsoft.com/slash/library//";
        Assert.AreEqual("http://msdn.microsoft.com/slash/library/site.aspx", UrlPathCombine(P1, "//site.aspx"));

        var path = UrlPathCombine("Http://MyUrl.com/", "Images/Image.jpg");

        Assert.AreEqual(
            "Http://MyUrl.com/Images/Image.jpg",
            path);
    }

我必须指出,Path.Combine似乎也能直接实现这一点,至少在.NET 4上是如此。

如果您不想在ASP.NET Core(也在Microsoft.Owin中提供)中添加第三方依赖项(如Flurl)或创建自定义扩展方法,则可以使用PathString来构建URI路径。然后,可以使用URI和UriBuilder的组合创建完整的URI。

在这种情况下,应为:

new Uri(new UriBuilder("http", "MyUrl.com").Uri, new PathString("/Images").Add("/Image.jpg").ToString())

这提供了所有组成部分,而无需在基URL中指定分隔符。不幸的是,PathString要求在每个字符串前面加上/,否则它实际上会引发ArgumentException!但至少您可以以易于单元测试的方式确定地构建URI。

如果您不想拥有像Flurl这样的依赖项,可以使用它的源代码:

    /// <summary>
    /// Basically a Path.Combine for URLs. Ensures exactly one '/' separates each segment,
    /// and exactly on '&amp;' separates each query parameter.
    /// URL-encodes illegal characters but not reserved characters.
    /// </summary>
    /// <param name="parts">URL parts to combine.</param>
    public static string Combine(params string[] parts) {
        if (parts == null)
            throw new ArgumentNullException(nameof(parts));

        string result = "";
        bool inQuery = false, inFragment = false;

        string CombineEnsureSingleSeparator(string a, string b, char separator) {
            if (string.IsNullOrEmpty(a)) return b;
            if (string.IsNullOrEmpty(b)) return a;
            return a.TrimEnd(separator) + separator + b.TrimStart(separator);
        }

        foreach (var part in parts) {
            if (string.IsNullOrEmpty(part))
                continue;

            if (result.EndsWith("?") || part.StartsWith("?"))
                result = CombineEnsureSingleSeparator(result, part, '?');
            else if (result.EndsWith("#") || part.StartsWith("#"))
                result = CombineEnsureSingleSeparator(result, part, '#');
            else if (inFragment)
                result += part;
            else if (inQuery)
                result = CombineEnsureSingleSeparator(result, part, '&');
            else
                result = CombineEnsureSingleSeparator(result, part, '/');

            if (part.Contains("#")) {
                inQuery = false;
                inFragment = true;
            }
            else if (!inFragment && part.Contains("?")) {
                inQuery = true;
            }
        }
        return EncodeIllegalCharacters(result);
    }

    /// <summary>
    /// URL-encodes characters in a string that are neither reserved nor unreserved. Avoids encoding reserved characters such as '/' and '?'. Avoids encoding '%' if it begins a %-hex-hex sequence (i.e. avoids double-encoding).
    /// </summary>
    /// <param name="s">The string to encode.</param>
    /// <param name="encodeSpaceAsPlus">If true, spaces will be encoded as + signs. Otherwise, they'll be encoded as %20.</param>
    /// <returns>The encoded URL.</returns>
    public static string EncodeIllegalCharacters(string s, bool encodeSpaceAsPlus = false) {
        if (string.IsNullOrEmpty(s))
            return s;

        if (encodeSpaceAsPlus)
            s = s.Replace(" ", "+");

        // Uri.EscapeUriString mostly does what we want - encodes illegal characters only - but it has a quirk
        // in that % isn't illegal if it's the start of a %-encoded sequence https://stackoverflow.com/a/47636037/62600

        // no % characters, so avoid the regex overhead
        if (!s.Contains("%"))
            return Uri.EscapeUriString(s);

        // pick out all %-hex-hex matches and avoid double-encoding 
        return Regex.Replace(s, "(.*?)((%[0-9A-Fa-f]{2})|$)", c => {
            var a = c.Groups[1].Value; // group 1 is a sequence with no %-encoding - encode illegal characters
            var b = c.Groups[2].Value; // group 2 is a valid 3-character %-encoded sequence - leave it alone!
            return Uri.EscapeUriString(a) + b;
        });
    }