为何这段代码不能向界面中添加

Question

 Dictionary<string, ClassLibrary3.CakeImage> list = cakeImageManager.SelectCakeImage();
            foreach (ClassLibrary3.CakeImage var in list.Values)
            {
                PictureBox pic = new PictureBox();
                pic.Image = Image.FromFile(var.IImage);
                pic.Tag = var.IID;
                pic.Size = new Size(220, 220);
                pic.SizeMode = PictureBoxSizeMode.AutoSize;
                pic.ContextMenuStrip = this.contextMenuStrip1;
                for (int i = 1; i <= 3; i++)
                {
                    for (int y = 0; y < 5; y++)
                    {
                        if (i == 1)
                            pic.Location = new Point(shu += 226, 1);
                        else if (i == 2)
                            pic.Location = new Point(shu += 226, 227);
                        else if (i == 3)
                            pic.Location = new Point(shu += 226, 453);
                        this.Controls.Add(pic);
                    }
                }
            }

Answer 1

this.Controls.Add(pic); 
pic.Visible=true;