如何在C#中创建只读对象属性？

Question

如下所示,用户可以更改只读产品字段/属性:

class Program
    {
        static void Main(string[] args)
        {
            var product = Product.Create("Orange");
            var order = Order.Create(product);
            order.Product.Name = "Banana"; // Main method shouldn't be able to change any property of product!
        }
    }

    public class Order
    {
        public Order(Product product)
        {
            this.Product = product;
        }

        public readonly Product Product;

        public static Order Create(Product product)
        {
            return new Order (product);
        }
    }

    public class Product
    {
        private Product(){}

        public string Name { get; set; }

        public static Product Create(string name)
        {
            return new Product { Name = name };
        }
    }

我认为这很基本,但似乎并非如此.

如何在C#中创建只读对象属性或字段？

谢谢,

Answer 1

该readonly关键字阻止您将新实例放入该字段.

它不会神奇地使字段内的任何对象不可变.
如果你写的话,你期望发生什么？

readonly Product x = Product.Create();

Product y;
y = x;
y.Name = "Changed!";

如果你想要一个不可变对象,你需要通过删除所有公共setter使类本身不可变.

Answer 2

您需要将Product的Name属性设置为private:

public class Product
{
    private Product(){}

    public string Name { get; private set; }

    public static Product Create(string name)
    {
        return new Product { Name = name };
    }
}