从集合里取出来的，还是原来的引用吗

gistfile1.cs

void Main()
{
    // 初始化一个context
    var cxt = new Context();
    cxt.StepModel1 = new StepModel1{ Name = "foo1" };
    cxt.StepModel2 = new StepModel2{ Name = "foo2" };
    
    // 从context一个方法的内部的集合中取出一个model
    var model1 =  cxt.GetStepModel(1);
    // 试着更新它
    var newModel = new StepModel1{ Name = "foo3" };
    model1 = newModel;
    // ! 失败鸟
    Console.WriteLine(cxt.StepModel1.Name);
}

// Define other methods and classes here
public class Context
{
	public StepModel1 StepModel1 {get;set;}
	public StepModel2 StepModel2 {get;set;}
	
	public IStepModel GetStepModel(int no)
	{
	   List<IStepModel> list = new List<IStepModel>{ this.StepModel1, this.StepModel2 };
	   return list.Single(m => m.No == no);
	}
}

public interface IStepModel
{
	int No {get;}
}

public class StepModel1 : IStepModel{
 public int No { get {return  1;}}
 public string Name {get;set;}
}

public class StepModel2 : IStepModel{
 public int No { get {return  2;}}
 public string Name {get;set;}
}

引用本身是按值copy的(by value)
var cxt = new Context();
// 创建了实例A，并且把对应的引用copy给了cxt的StepModel1字段
cxt.StepModel1 = new StepModel1{ Name = "foo1" };
cxt.StepModel2 = new StepModel2{ Name = "foo2" };

// 创建了实例B，并且把对应的引用copy给了newModel变量
var newModel = new StepModel1{ Name = "foo3" };

// GetStepModel是实例A的引用，这个应该没问题吧
// 然后将此引用copy到了model1变量
var model1 = cxt.GetStepModel(1);

// 修改了model1变量（model1不再是实例A的引用，而是实例B的引用）
model1 = newModel;

// 好吧，重新去StepModel1的那个引用，不过谁也没改过这个引用，所以它依然是一个指向实例A的引用
Console.WriteLine(cxt.StepModel1.Name);