一个画无限条直线的MFC程序

我要画无限条直线，代码如下，我检查过，代码应该是没什么问题的，就是显示不出来，为什么，我是用vs2017写的，求前辈指导
Cobject.h
class graph:public CObject
{
public:
    int x0, x1, y0, y1;
    graph() { x0 = x1 = y0 = y1 = 0; }
    virtual void Cair(){}
    virtual void Draw(CDC*pDC){}
};
class Line :public graph
{
public:
    Line() { x0 = x1 = y0 = y1 = 0; }
    virtual ~Line(){}
    void Draw(CDC*pDC)
    {
        pDC->MoveTo(x0, y0);
        pDC->MoveTo(x1, y1);
    }
};

CCMZTEXT3View.h部分核心代码
#include"Cobject.h"
class CCMZTEXT3View : public CView
{
protected: // 仅从序列化创建
    CCMZTEXT3View() noexcept;
    DECLARE_DYNCREATE(CCMZTEXT3View)

// 特性
public:
    CCMZTEXT3Doc* GetDocument() const;
    int DrawWhat;
    CTypedPtrArray<CObArray, graph*>m_graph;
    graph *g;
    bool IsDown;
CCMZTEXT3View.cpp部分核心代码
CCMZTEXT3View::CCMZTEXT3View() noexcept
{
    IsDown = false;
    DrawWhat = 1;
    // TODO: 在此处添加构造代码

}
void CCMZTEXT3View::OnDraw(CDC* pDC)
{
    CCMZTEXT3Doc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    if (!pDoc)
        return;
    int i = m_graph.GetSize(), j;
    for (j = 0; j < i; j++)
    {
        graph*pObject = m_graph[j];
        pObject->Draw(pDC);
    }
    if (IsDown)
    {
        g->Draw(pDC);
    }
void CCMZTEXT3View::OnLButtonDown(UINT nFlags, CPoint point)
{
    // TODO: 在此添加消息处理程序代码和/或调用默认值
    IsDown = true;
    if (DrawWhat == 1)
    {
        g = new Line();
        g->x0 = point.x;
        g->y0 = point.y;
    }
    CView::OnLButtonDown(nFlags, point);
}
void CCMZTEXT3View::OnLButtonUp(UINT nFlags, CPoint point)
{
    // TODO: 在此添加消息处理程序代码和/或调用默认值
    IsDown = false;
    m_graph.Add(g);
    CView::OnLButtonUp(nFlags, point);
}
void CCMZTEXT3View::OnMouseMove(UINT nFlags, CPoint point)
{
    // TODO: 在此添加消息处理程序代码和/或调用默认值
    if (IsDown)
    {
        g->x1 = point.x;
        g->y1 >= point.y;
        Invalidate();
    }
    CView::OnMouseMove(nFlags, point);
}
void CCMZTEXT3View::OnLine()
{
    DrawWhat = 1;
    // TODO: 在此添加命令处理程序代码
}
我已经在菜单栏中添加的画直线的ID了，ID是ID_line；