public static extern bool GetTextExtentExPointW(IntPtr hDc, string lpString, int nLength, int nMaxExtent, int[] lpnFit, int[] alpDx, out Size size);

        GetTextExtentExPointW(hDC, testString, testString.Length, width, fit, charExtents, out sz);

[DllImport("gdi32.dll",EntryPoint="GetTextExtentExPointW")]

static extern bool GetTextExtentExPoint(IntPtr hdc, [MarshalAs(UnmanagedType.LPWStr)] string lpszStr,