c++ accesse violation while trying to open camera when debugging - c++

Question

#include <opencv2/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include "opencv2/opencv.hpp"
#include <opencv2/highgui.hpp>
#include <iostream>
#include <Windows.h>
#pragma comment(lib, "vfw32.lib")
#pragma comment( lib, "comctl32.lib" )
using namespace cv;
using namespace std;
int main(int argc, char** argv)
{
Mat edges;
VideoCapture cap;
try
{
cap.open(0); // open the default camera
}
catch (...)
{
cout << "error!!" << endl;
}
if (!cap.isOpened()) // check if we succeeded
return -1;
namedWindow("edges", 1);
for (;;)
{
Mat frame;
cap >> frame; // get a new frame from camera
edges = frame;
GaussianBlur(edges, edges, Size(7, 7), 1.5, 1.5);
imshow("edges", edges);
if (waitKey(30) >= 0) break;
}
return 0;
}
when i try to run this code in the command line it runs perfectly, but when i try to debug it in visual studio express 2013 it crashing at the line "cap.open(0);"
the errror is :
Unhandled exception at 0x0C028EFB in opencv_1.exe: 0xC0000005: Access violation executing location 0x0C028EFB.
i dont know what the problem is or how to fix it.
sorry for bad english