C# out Keyword

In C#, out keyword 是argument传值变成passed by reference. out keyword 在同时返回多个值时很有用.

与ref keyword 相似. 若是使用out keyword传argument, 那么在method 的definition 和 使用时都需要家out keyword. 

Async methods can't use out keyword.

Differences between out keyword and ref keyword:

ref requires that variable be initialized before it is passed.

class OutReturnExample
{
    static void Method(out int i, out string s1, out string s2)
    {
        i = 44;
        s1 = "I've been returned";
        s2 = null;
    }
    static void Main()
    {
        int value;
        string str1, str2;
        Method(out value, out str1, out str2);
        // value is now 44
        // str1 is now "I've been returned"
        // str2 is (still) null;
    }
}