我尝试使用MouseWheel缩放图像，但不起作用

Question

我尝试使用鼠标滚轮启用缩放功能，但是当我启动项目时缩放功能不起作用

我的代码

Form1.Designer.cs

        this.Panel4.AutoScroll = true;
        this.Panel4.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D;
        this.Panel4.Controls.Add(this.pictureBox4);
        this.Panel4.Controls.Add(this.pictureBox3);
        this.Panel4.Location = new System.Drawing.Point(175, 353);
        this.Panel4.Name = "Panel4";
        this.Panel4.Size = new System.Drawing.Size(1163, 365);
        this.Panel4.TabIndex = 7;

Form1.cs

添加MouseWheel事件

 InitializeComponent();
 Panel4.MouseWheel += new MouseEventHandler(Panel4_MouseWheel);

当我滚动鼠标滚轮时，此功能处于活动状态

private void Panel4_MouseWheel(object sender, MouseEventArgs e)
    {
        Console.WriteLine("Zoom!!");
        this.Focus();
        // or Panel4.Focus();
        if (e.Delta < 120 && zoomIn_zoomOut > 1)
        {
            zoomIn_zoomOut--;
            zoom_len -= zoomIn_zoomOut;
        }
        else if (e.Delta >= 120)
        {
            zoomIn_zoomOut++;
            zoom_len += zoomIn_zoomOut;
        }

        factor = new Size(zoomIn_zoomOut, 1);
        zoom_pic(factor, e);
    }


void zoom_pic(Size scale, MouseEventArgs e)
    {

        // Calculate and zoom Picture
    }

期望结果

Zoom!!

实际结果

(show nothing)

您能告诉我这段代码是什么问题吗？我没有办法解决。

非常感谢您