我试图在groupbox中动态添加一个按钮，但是这个按钮在groupbox工具后面，不能被看到或者不能被点击。我需要我的按钮在groupbox中被看到并且可以被点击。下面是我的代码：

namespace HarryPotter
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {           
            GroupBox grp = new GroupBox();
            grp.Top = 600;
            grp.Left = 0;
            grp.Text = "Kontroller";
            grp.Size = new Size(600, 400);
            //grp.BackgroundImage = Properties.Resources.hogwartscastle;
            //grp.BackgroundImageLayout = System.Windows.Forms.ImageLayout.Stretch;
            grp.FlatStyle = FlatStyle.Flat;
            this.Controls.Add(grp);

            Button btn2 = new Button();
            btn2.Size = new Size(40, 40);
            btn2.Top = 580;
            btn2.Left = 0;
            btn2.Parent = grp;
            btn2.BackgroundImage = Image.FromFile(Environment.GetFolderPath(Environment.SpecialFolder.Desktop) + @"\DownArrow.png");
            btn2.BackgroundImageLayout = System.Windows.Forms.ImageLayout.Stretch;
            grp.Controls.Add(btn2);
            this.Controls.Add(btn2);

        }
    }
}

下面是截图：