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;
        });
    }

这可能是一个合适的简单解决方案：

public static string Combine(string uri1, string uri2)
{
    uri1 = uri1.TrimEnd('/');
    uri2 = uri2.TrimStart('/');
    return string.Format("{0}/{1}", uri1, uri2);
}

我发现Uri构造函数将“\”转换为“/”。因此，您也可以将Path.Combine与Uri构造函数一起使用。

 Uri baseUri = new Uri("http://MyUrl.com");
 string path = Path.Combine("Images", "Image.jpg");
 Uri myUri = new Uri(baseUri, path);

Uri有一个构造函数可以为您执行此操作：new Uri（Uri baseUri，string relativeUri）

下面是一个示例：

Uri baseUri = new Uri("http://www.contoso.com");
Uri myUri = new Uri(baseUri, "catalog/shownew.htm");

编辑注意：小心，这种方法并不能像预期的那样工作。在某些情况下，它可以剪切baseUri的一部分。查看评论和其他答案。

这是我的方法，我也会自己使用：

public static string UrlCombine(string part1, string part2)
{
    string newPart1 = string.Empty;
    string newPart2 = string.Empty;
    string seperator = "/";

    // If either part1 or part 2 is empty,
    // we don't need to combine with seperator
    if (string.IsNullOrEmpty(part1) || string.IsNullOrEmpty(part2))
    {
        seperator = string.Empty;
    }

    // If part1 is not empty,
    // remove '/' at last
    if (!string.IsNullOrEmpty(part1))
    {
        newPart1 = part1.TrimEnd('/');
    }

    // If part2 is not empty,
    // remove '/' at first
    if (!string.IsNullOrEmpty(part2))
    {
        newPart2 = part2.TrimStart('/');
    }

    // Now finally combine
    return string.Format("{0}{1}{2}", newPart1, seperator, newPart2);
}

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);
    }