程序代码：

    public partial class PictureBox : Control
    { 
        private string ItemID;
        [Category("Item ID"), DescriptionAttribute("物品编号"),DefaultValue(null),Browsable(true)]
        public string itemID
        {
            get { return this.ItemID; }
            set { this.ItemID = value; }
        }
    }

程序代码：

    public class PictureBoxEx : PictureBox
    { 
        public PictureBoxEx(){}

        private string ItemID;
        [Category("Item ID"), DescriptionAttribute("物品编号"),DefaultValue(null),Browsable(true)]
        public string itemID
        {
            get { return this.ItemID; }
            set { this.ItemID = value; }
        }
    }

pictureBox1.ItemID = "12345";