帮我看个代码


 1namespace InterfaceExample
 2{
 3    public class Computer
 4    {
 5        private IMobileStorage _usbDrive;
 6
 7        public IMobileStorage UsbDrive
 8        {
 9            get
10            {
11                return this._usbDrive;
12            }
13            set
14            {
15                this._usbDrive = value;
16            }
17        }
18
19        public Computer()
20        {
21        }
22
23        public Computer(IMobileStorage usbDrive)
24        {
25            this.UsbDrive = usbDrive;
26        }
27    
28        public void ReadData()
29        {
30            this._usbDrive.Read();
31        }
32
33        public void WriteData()
34        {
35            this._usbDrive.Write();
36        }
37    }
38}
我想请教一下 第7行 重新定义个 UsbDrive 有什么好处？代码中，UsbDrive就是给_UsbDrive赋值，直接给_UsbDrive赋值不就可以了吗？而且用UsbDrive并没有杜绝_UsbDrive的使用额请教。。谢谢