[DllImport("shlwapi.dll", EntryPoint = "PathIsRootW",  SetLastError = True, CharSet = CharSet.Unicode)]

static extern bool PathIsRoot([MarshalAs(UnmanagedType.LPTStr)]string pszPath);

<DllImport("shlwapi.dll", EntryPoint:="PathIsRootW",  SetLastError:=True, CharSet:=CharSet.Unicode)> _

Public Function PathIsRoot(<MarshalAs(UnmanagedType.LPTStr)>pszPath As String) As <MarshalAs(UnmanagedType.Bool)> Boolean

Public Declare Function PathIsRoot Lib "shlwapi" Alias "PathIsRootA" _