C#引用数据类型特点以及ref的使用

先贴代码

namespace ConsoleApplication6
{
class Program
{
static void Main(string[] args)
{
Test1();
Test2();
Test3();
}
private static void Test1()
{
var a = new DataModel() { Value = 1 };
var b = a;
a = new DataModel() { Value = 2 };
Console.WriteLine($"a = {a.Value}");
Console.WriteLine($"b = {b.Value}");
//Output: a=2 b=1

}
private static void Test2()
{
var a = new DataModel() { Value = 1 };
ChangeVal(a);
Console.WriteLine($"a = {a.Value}");
//Output: a=1 b=1 c=2

}
private static void Test3()
{
var a = new DataModel() { Value = 1 };
ChangeVal(ref a);
Console.WriteLine($"a = {a.Value}");
//Output: a=2 b=1 c=2

}
private static void ChangeVal(DataModel c)
{
var b = c;
c = new DataModel() { Value = 2 };
Console.WriteLine($"b = {b.Value}");
Console.WriteLine($"c = {c.Value}");
}
private static void ChangeVal(ref DataModel c)
{
var b = c;
c = new DataModel() { Value = 2 };
Console.WriteLine($"b = {b.Value}");
Console.WriteLine($"c = {c.Value}");
}
}
public class DataModel
{
public int Value { get; set; }
}
}

Test1() b=a之后b指向了同一块内存地址，a重新赋值后a指向了另一块内存地址

Test2() 函数传递参数，实际地址发生了改变，参数重新实例化后，指向了另一个内存地址

Test3() 使用ref关键字后传递了一样的地址，所以后面修改c的值就是修改a的值