释放内存失败，位图DC为什么不能释放

Question

我做了个查看位图的程序，每次换图时需要把前一图申请的内存释放掉，但是每次free完就产生异常

if (data != NULL)
                {
                    DeleteObject(hBit);
                    ReleaseDC(hWnd,memDC); //并不能释放DC，每次返回的都是0
                    ReleaseDC(hWnd,winDC);
                    DeleteObject(memDC); //只有这样才能释放
                    free(data); //产生异常
                }
                szFile = OpenBmp(hWnd);
                if (szFile != NULL)
                {
                    wcscpy_s(fName, lstrlen(szFile) * 2, szFile);
                }
                else
                    return NULL;
                hFile = CreateFile(fName, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
                R = ReadFile(hFile, &bfh, sizeof(BITMAPFILEHEADER), &num, NULL);
                if (R)
                {
                    R = ReadFile(hFile, &fif, sizeof(BITMAPINFOHEADER), &num, NULL);
                    winDC = GetDC(hWnd);
                    memDC = CreateCompatibleDC(winDC);
                    GetClientRect(hWnd, &rect);
                    dataSize = bfh.bfSize - bfh.bfOffBits;
                    data = (BYTE*)malloc(dataSize);

                    pbmi.bmiHeader = fif;
                    width = fif.biWidth;
                    height = fif.biHeight;

                    hBit = CreateDIBSection(memDC, &pbmi, DIB_RGB_COLORS, (void**)&data, NULL, 0);
                    R = ReadFile(hFile, data, dataSize, &num, NULL);
                    SelectObject(memDC, hBit);
                    open = TRUE;
                    InvalidateRect(hWnd, &rect, TRUE);

                }
                CloseHandle(hFile);

Answer 1

看看句柄是否有效，是否已经释放过了