C＃的返回值和参数的语义是否与Java相同？

Question

我想通过Unity学习C＃，我想知道C＃在传递参数或返回值的按引用或按值传递时是否具有与Java相同的语义？

我在C＃语言中看到，您可以使用它ref来指示某些东西是通过引用传递的，这是否意味着默认情况下它是通过值传递的？

默认情况下，除非引用是原始类型，否则Java默认通过引用传递（即，不从扩展的东西Object）

这包括Java中的数组。但是我不确定C＃。

Answer 1

对于原始类型和非原始类型，Java总是按值传递。

例如，

void JavaMethod(int i, Foo f)
{
    i = 9; //not changed from caller's point of view
    f = new Foo(); //not changed from caller's point of view
}

C# is pass-by-value unless the 'ref' keyword is used:

void CSharpMethod(int i, Foo f, ref int j, ref Bar b)
{
    i = 9; //not changed from caller's point of view
    f = new Foo(); //not changed from caller's point of view

    j = 9; //changed from caller's point of view
    b = new Bar(); //changed from caller's point of view
}

In both languages, you can modify the internal state of an non-primitive object when it is passed by value:

void JavaOrCSharpMethod(Foo f)
{
    f.field = 9; //internal state is changed from caller's point of view
}

Keep in mind the difference between assigning a new instance to a parameter and modifying the internal state of the object. Not understanding this is the source of a lot of confusion about this subject.

Also, there is no real substance in whether a primitive type or non-primitive type is used, other than the fact that primitive types do not have members which change their state, so it's always done via assignment. Any non-primitive type where state can only be changed via assignment would seem the same.

I would include some C++ examples also, but this would drastically complicate the discussion since C++ has many ways of implementing pass-by-reference.