Remove the last character if it's DirectorySeparatorChar with C#

I need to extract the path info using Path.GetFileName(), and this function doesn't work when the last character of the input string is Director开发者_JS百科ySeparatorChar('/' or '\').

I came up with this code, but it's too lengthy. Is there a better way to go?

string lastCharString = fullPath.Substring (fullPath.Length-1);
char lastChar = lastCharString[0];

if (lastChar == Path.DirectorySeparatorChar) {
    fullPath = fullPath.Substring(0, fullPath.Length-1);
}

fullPath = fullPath.TrimEnd(Path.DirectorySeparatorChar);

// If the fullPath is not a root directory
if (Path.GetDirectoryName(fullPath) != null)
    fullPath = fullPath.TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);

while(fullPath.EndsWith(Path.DirectorySeparatorChar.ToString())){
   fullPath = fullPath.Substring(0, fullPath.Length-1);
}

string path1 =  @"c:\directory\";
string path2 = @"c:\directory\file.txt";
string path3 = @"c:\directory";

Console.WriteLine(Path.Combine(Path.GetDirectoryName(path1), Path.GetFileName(path1)));
Console.WriteLine(Path.Combine(Path.GetDirectoryName(path2), Path.GetFileName(path2)));
Console.WriteLine(Path.Combine(Path.GetDirectoryName(path3), Path.GetFileName(path3)));

Gives:

c:\directory
c:\directory\file.txt
c:\directory

Hope it helps.

fullPath = Path.GetFileName(
    fullPath.Split(
        new [] { Path.DirectorySeparatorChar }, 
        StringSplitOptions.RemoveEmptyEntries
    ).Last()
)

Based on Marino Šimić's answer and Dima's comment here is a solution which will not fail on C: and C:\:

var newPath = Path.Combine(Path.GetDirectoryName(oldPath) ?? oldPath, Path.GetFileName(oldPath));