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

static extern IntPtr PathAddBackslash([MarshalAs(UnmanagedType.LPTStr)]System.Text.StringBuilder lpszPath);

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

Public Function PathAddBackslash(<MarshalAs(UnmanagedType.LPTStr)>lpszPath As System.Text.StringBuilder) As IntPtr

Public Declare Function PathAddBackslash Lib "shlwapi" Alias "PathAddBackslashA" _