重载WM_NCLBUTTONDOWN消息
在.h文件中声明

afx_msg void OnNcLButtonDown(UINT nHitTest, CPoint point);

在.cpp文件中实现

void MeetingFullScreenDlg::OnNcLButtonDown(UINT nHitTest, CPoint point)
{
    if (HTCAPTION == nHitTest)
    {
        return;
    }
    CDialog::OnNcLButtonDown(nHitTest, point);
}

BEGIN_MESSAGE_MAP中添加消息

    ON_WM_NCLBUTTONDOWN()