public static string GetDirectoryName(string path)
{
// LAMESPEC: For empty string MS docs say both
// return null AND throw exception. Seems .NET throws.
if (path == String.Empty)
{
throw new ArgumentException();
}
if (path == null || GetPathRoot(path) == path)
{
return(null);
}
CheckArgument.WhitespaceOnly(path);
CheckArgument.PathChars(path);
int nLast = path.LastIndexOfAny(PathSeparatorChars);
if (nLast == 0)
{
nLast++;
}
if (nLast > 0)
{
string ret = path.Substring(0, nLast);
int l = ret.Length;
if (l >= 2 && ret[l - 1] == VolumeSeparatorChar)
{
return(ret + DirectorySeparatorChar);
}
else
{
return(ret);
}
}
return(String.Empty);
}