我可以修改传递方法参数 [英] Can I modify a passed method parameter

问题描述

我的直觉说我不应该做到以下几点。我没有得到任何警告一下吧。

my gut feeling says I shouldn't do the following. I don't get any warnings about it.

void test(DateTime d)
{
 d = d.AddDays(2);
//do some thing with d
 }

或这更恰当

 void test(DateTime d)
 {
 DateTime _d = d.AddDays(1);
//do some thing with _d
 }

有关某种原因，我有总是处理就像在第二个例子中传递的参数。
但我不知道这是否是真的nessesry ...也许这只是unnessary代码。

For some reason I have always handled passed parameters like in the second example. But I am not sure if it's really nessesry...maybe it's just unnessary code.

我不打算调用的方法将采用改良值。
任何人有任何意见

I am not thinking that the calling method would be using the modified value. anyone have any opinions

推荐答案

更改为参数的值的是不可见的来电者，除非它是一个 REF 或退出参数。

Changes to the value of a parameter are invisible to the caller, unless it's a ref or out parameter.

这是的不的，如果你更改了一个引用类型对象的情况下的简称的一个参数。例如：

That's not the case if you make a change to an reference type object referred to by a parameter. For example:

public void Foo(StringBuilder b)
{
    // Changes the value of the parameter (b) - not seen by caller
    b = new StringBuilder();
}

public void Bar(StringBuilder b)
{
    // Changes the contents of the StringBuilder referred to by b's value -
    // this will be seen by the caller
    b.Append("Hello");
}

最后，如果该参数是按引用传递，变化的是的看出：

public void Baz(ref StringBuilder b)
{
    // This change *will* be seen
    b = new StringBuilder();
}

有关更多相关信息，请参阅我的文章参数传递。

For more on this, see my article on parameter passing.

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