什么是ref和out?如何在asp.net中使用? [英] What is ref and out and how to use in asp.net ?

问题描述

什么是ref和out，以及如何在asp.net中使用?
请举例说明.

What is ref and out and how to use in asp.net ?
Please explain with an example .

推荐答案

ref和out控制如何将数据传递给您的方法.

通常，参数按值传递-变量的副本被复制并传递.因此，您对方法中的变量所做的任何更改都将被丢弃.

ref and out control how data is passed through to your methods.

Normally, a parameter is passed by value - a copy of the variable is made and is passed through. So any changes you make to teh variable inside your method are discarded.

{
    string s = "hello";
    MyMethod(s);
    Console.WriteLine(s);
    }
void MyMethod(string str)
    {
    str = "goodbye";
    }

打印"hello"，因为复制了"s"变量.
ref更改了-传递的是对"s"的引用:

Prints "hello", because the "s" variable was copied.
ref changes that - what is passed through is a reference to "s":

{
    string s = "hello";
    MyMethod(ref s);
    Console.WriteLine(s);
    }
void MyMethod(ref string str)
    {
    str = "goodbye";
    }

打印再见"，因为该方法现在可以影响外部变量.
out的功能大致相同，但是MyMethod不能使用"s"变量的外部值-它只能设置外部值:

Prints "goodbye" because the method can now affect the outer variable.
out does much the same thing, but the external value of the "s" varaible is not available to MyMethod - it can just set the external value:

    {
    string s;
    MyMethod(out s);
    Console.WriteLine(s);
    }
void MyMethod(out string str)
    {
    str = "goodbye";
    }

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