结构体属性使用set和get访问器时，只能通过"="赋值对属性进行改变，因为你永远只能访问到属性的副本，不会改变属性本身。

using UnityEngine;
using System.Collections;

public class Test:MonoBehaviour{
	
	private Vector2 m_size;
	public Vector2 size{get; private set;}

	private void Start(){
		m_size.Set(1,1);
		Debug.Log("m_size:"+m_size);//output: m_size:(1.0, 1.0)

		size.Set(1,1);
		Debug.Log("sizeA:"+size);//ouput: sizeA:(0.0, 0.0)

		size=new Vector2(0.5f,0.5f);
		Debug.Log("sizeB:"+size);//ouput: sizeB:(0.5, 0.5)

		size.Set(0.6f,0.6f);
		Debug.Log("sizeC:"+size);//ouput: sizeC:(0.5, 0.5)
	}
}