//引入命名空间
using System;
using System.Windows.Forms;
using System.Drawing;

    public class MyContainer : ScrollableControl, IContainerControl
    {
        private Control activeControl;
        public MyContainer() 
        {
            // Make the container control Blue so it can be distinguished on the form.
            this.BackColor = Color.Blue;
            
            // Make the container scrollable.
            this.AutoScroll = true;
        }

        // Add implementation to the IContainerControl.ActiveControl property.
        public Control ActiveControl
        {
            get
            {
                return activeControl;
            }

            set
            {
                // Make sure the control is a member of the ControlCollection.
                if(this.Controls.Contains(value))
                {
                    activeControl = value;
                }
            }
        }

        // Add implementations to the IContainerControl.ActivateControl(Control) method.
        public bool ActivateControl(Control active)
        {
            if(this.Controls.Contains(active))
            {
                // Select the control and scroll the control into view if needed.
                active.Select();
                this.ScrollControlIntoView(active);
                this.activeControl = active;
                return true;
            }
            return false;
        }
    }