error for Create MEX-File from OpenCV C++ file

i am using MATLAB 2015b and install opencv interface According to this link: http://www.mathworks.com/help/vision/ug/opencv-interface.html samples were well executed (No error). but for compile my cpp file by mexOpenCV.m function , I encountered this error :

   Error using mexOpenCV (line 122)
   LINK : error LNK2001: unresolved external symbol mexFunction
   main.lib : fatal error LNK1120: 1 unresolved externals

include for my cpp file is :

   #include "opencvmex.hpp"
   #include <opencv2/highgui/highgui.hpp>
   #include <iostream>

[James Tursa]

The error states there was no mexFunction found. Can you verify that mexFunction is in one of your source files, and that you are listing this file in the mex command?