用于在路径列表中筛选顶级目录的算法，C#

这个怎么样：

string inputDir = "/dir1/subdir/sub-subdir";
string [] Split = inputDir.Split(new Char [] {'/'}, StringSplitOptions.RemoveEmptyEntries); 
string outputDir = Split[0];

List<string> result= new List<string>();  
foreach (string i in input)
{
   string[] tmp = i.split(@"/");
   result.add(@"/" + tmp[0]);
}