组合它们并确保始终正确的一种简单方法是：

string.Format("{0}/{1}", Url1.Trim('/'), Url2);

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

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);
}

上面有托德·梅尼尔（Todd Menier）的评论，Flurl包括一个Url.Combine。

更多详情：

Url.Combine基本上是Url的Path.Combine，确保部分之间只有一个分隔符：

var url = Url.Combine(
    "http://MyUrl.com/",
    "/too/", "/many/", "/slashes/",
    "too", "few?",
    "x=1", "y=2"
// result: "http://www.MyUrl.com/too/many/slashes/too/few?x=1&y=2" 

在NuGet上获取Flurl.Http：

PM>安装包Flurl.Http

或者获取没有HTTP功能的独立URL生成器：

PM>安装程序包Flurl

我创建了这个功能，可以让您的生活更轻松：

    /// <summary>
    /// The ultimate Path combiner of all time
    /// </summary>
    /// <param name="IsURL">
    /// true - if the paths are Internet URLs, false - if the paths are local URLs, this is very important as this will be used to decide which separator will be used.
    /// </param>
    /// <param name="IsRelative">Just adds the separator at the beginning</param>
    /// <param name="IsFixInternal">Fix the paths from within (by removing duplicate separators and correcting the separators)</param>
    /// <param name="parts">The paths to combine</param>
    /// <returns>the combined path</returns>
    public static string PathCombine(bool IsURL , bool IsRelative , bool IsFixInternal , params string[] parts)
    {
        if (parts == null || parts.Length == 0) return string.Empty;
        char separator = IsURL ? '/' : '\\';

        if (parts.Length == 1 && IsFixInternal)
        {
            string validsingle;
            if (IsURL)
            {
                validsingle = parts[0].Replace('\\' , '/');
            }
            else
            {
                validsingle = parts[0].Replace('/' , '\\');
            }
            validsingle = validsingle.Trim(separator);
            return (IsRelative ? separator.ToString() : string.Empty) + validsingle;
        }

        string final = parts
            .Aggregate
            (
            (string first , string second) =>
            {
                string validfirst;
                string validsecond;
                if (IsURL)
                {
                    validfirst = first.Replace('\\' , '/');
                    validsecond = second.Replace('\\' , '/');
                }
                else
                {
                    validfirst = first.Replace('/' , '\\');
                    validsecond = second.Replace('/' , '\\');
                }
                var prefix = string.Empty;
                if (IsFixInternal)
                {
                    if (IsURL)
                    {
                        if (validfirst.Contains("://"))
                        {
                            var tofix = validfirst.Substring(validfirst.IndexOf("://") + 3);
                            prefix = validfirst.Replace(tofix , string.Empty).TrimStart(separator);

                            var tofixlist = tofix.Split(new[] { separator } , StringSplitOptions.RemoveEmptyEntries);

                            validfirst = separator + string.Join(separator.ToString() , tofixlist);
                        }
                        else
                        {
                            var firstlist = validfirst.Split(new[] { separator } , StringSplitOptions.RemoveEmptyEntries);
                            validfirst = string.Join(separator.ToString() , firstlist);
                        }

                        var secondlist = validsecond.Split(new[] { separator } , StringSplitOptions.RemoveEmptyEntries);
                        validsecond = string.Join(separator.ToString() , secondlist);
                    }
                    else
                    {
                        var firstlist = validfirst.Split(new[] { separator } , StringSplitOptions.RemoveEmptyEntries);
                        var secondlist = validsecond.Split(new[] { separator } , StringSplitOptions.RemoveEmptyEntries);

                        validfirst = string.Join(separator.ToString() , firstlist);
                        validsecond = string.Join(separator.ToString() , secondlist);
                    }
                }
                return prefix + validfirst.Trim(separator) + separator + validsecond.Trim(separator);
            }
            );
        return (IsRelative ? separator.ToString() : string.Empty) + final;
    }

它适用于URL和普通路径。

用法：

    // Fixes internal paths
    Console.WriteLine(PathCombine(true , true , true , @"\/\/folder 1\/\/\/\\/\folder2\///folder3\\/" , @"/\somefile.ext\/\//\"));
    // Result: /folder 1/folder2/folder3/somefile.ext

    // Doesn't fix internal paths
    Console.WriteLine(PathCombine(true , true , false , @"\/\/folder 1\/\/\/\\/\folder2\///folder3\\/" , @"/\somefile.ext\/\//\"));
    //result : /folder 1//////////folder2////folder3/somefile.ext

    // Don't worry about URL prefixes when fixing internal paths
    Console.WriteLine(PathCombine(true , false , true , @"/\/\/https:/\/\/\lul.com\/\/\/\\/\folder2\///folder3\\/" , @"/\somefile.ext\/\//\"));
    // Result: https://lul.com/folder2/folder3/somefile.ext

    Console.WriteLine(PathCombine(false , true , true , @"../../../\\..\...\./../somepath" , @"anotherpath"));
    // Result: \..\..\..\..\...\.\..\somepath\anotherpath