public extern static Int32 GetThemePartSize(IntPtr hTheme, IntPtr hdc, WindowPart part, WindowPartState state, ref RECT pRect, ThemeSize eSize, out SIZE size);

public extern static Int32 GetThemePartSize(IntPtr hTheme, IntPtr hdc,WindowPart part, WindowPartState state, int pRect, ThemeSize eSize, out SIZE size);

Public Declare Function GetThemePartSize Lib "uxtheme.dll" (ByVal hTheme As IntPtr, ByVal hdc As IntPtr, ByVal iPartId As Integer, ByVal iStateId As Integer, ByRef prc As Rectangle, ByVal eSize As THEMESIZE, ByRef psz As Size) As Integer