The answer is mainly because I saw that you have more points. . . So I wrote an example for you. There's not much to say, it's similar to pointers in C language. If ref is not added, the value is assigned when the function parameter is passed, and the operations inside the function will not affect the outside. Adding ref means it has the same value as the outside.

static?void?Main(string[]?args)

{

int?a?=?2;

int?b?=?3;

Console.WriteLine("a={0},b={1}",?a,?b);

Swap(ref?a,?ref?b) ;//?2,?3

Console.WriteLine("a={0},b={1}",?a,?b);

Console.ReadLine ();//?3,?2

}

static?void?Swap(ref?int?a,?ref?int?b)

{

int?c?=?a;

a?=?b;

b?=?c;

}