C#中的工厂模式：如何确保对象实例只能由工厂类创建

工厂模式：确保对象实例只能由工厂类创建

csharp
using System;
// 图形接口
public interface IShape
{
    void Draw();
}
// 圆形类
public class Circle : IShape
{
    public void Draw()
    {
        Console.WriteLine("绘制一个圆形");
    }
}
// 正方形类
public class Square : IShape
{
    public void Draw()
    {
        Console.WriteLine("绘制一个正方形");
    }
}
// 工厂类
public class ShapeFactory
{
    public static IShape CreateShape(string shapeType)
    {
        switch (shapeType)
        {
            case "circle":
                return new Circle();
            case "square":
                return new Square();
            default:
                throw new ArgumentException("不支持的图形类型");
        }
    }
}
// 客户端代码
public class Client
{
    public static void Main()
    {
        IShape circle = ShapeFactory.CreateShape("circle");
        circle.Draw();
        IShape square = ShapeFactory.CreateShape("square");
        square.Draw();
    }
}