/// <summary>Returns the directory information for the specified path string.</summary>
/// <returns>A <see cref="T:System.String" /> containing directory information for <paramref name="path" />, or null if <paramref name="path" /> denotes a root directory or is null. Returns <see cref="F:System.String.Empty" /> if <paramref name="path" /> does not contain directory information.</returns>
/// <param name="path">The path of a file or directory. </param>
/// <exception cref="T:System.ArgumentException">The <paramref name="path" /> parameter contains invalid characters, is empty, or contains only white spaces. </exception>
/// <exception cref="T:System.IO.PathTooLongException">The <paramref name="path" /> parameter is longer than the system-defined maximum length.</exception>
/// <filterpriority>1</filterpriority>
public static string GetDirectoryName(string path)
{
if (path == string.Empty)
{
throw new ArgumentException("Invalid path");
}
if (path == null || Path.GetPathRoot(path) == path)
{
return(null);
}
if (path.Trim().Length == 0)
{
throw new ArgumentException("Argument string consists of whitespace characters only.");
}
if (path.IndexOfAny(Path.InvalidPathChars) > -1)
{
throw new ArgumentException("Path contains invalid characters");
}
int num = path.LastIndexOfAny(Path.PathSeparatorChars);
if (num == 0)
{
num++;
}
if (num <= 0)
{
return(string.Empty);
}
string text = path.Substring(0, num);
int length = text.Length;
if (length >= 2 && Path.DirectorySeparatorChar == '\\' && text[length - 1] == Path.VolumeSeparatorChar)
{
return(text + Path.DirectorySeparatorChar);
}
return(Path.CleanPath(text));
}