超载或可选参数之间的性能差异？

问题描述：

没有，没有回答有↑

我不知道是否应该在C＃中使用可选参数。到现在为止我一直重载方法。但可选参数都不错过，更清洁，更少的代码。我用他们在其他语言，所以我也以某种方式使用它们。有什么，讲反对使用它们？性能是我的第一个关键点。难道降？

示例代码：

I wonder if I should be using optional parameters in C#. Until now I was always overloading methods. But optional parameters are nice too, cleaner and less code. And I use them in other languages so I'm also used to them in some way. Is there anything that speaks against using them ? Performance is the first key point for me. Would it drop ?

Example code:

class Program
{
    // overloading
    private static void test1(string text1)
    {
        Console.WriteLine(text1 + " " + "world");
    }

    private static void test1(string text1, string text2)
    {
        Console.WriteLine(text1 + " " + text2);
    }

    // optional parameters
    private static void test2(string text1, string text2 = "world")
    {
        Console.WriteLine(text1 + " " + text2);
    }

    static void Main(string[] args)
    {
        test1("hello");
        test1("hello", "guest");

        test2("hello"); // transforms to test2("hello", "world"); ?
        test2("hello", "guest");

        Console.ReadKey();
    }
}

我测量的时间需要几百万超载呼叫和可选参数呼叫。

I measured the time needed for a few millions overload calls and optional parameter calls.

可选参数与字符串：18％的慢（2个参数，发布）

可选参数与整数：其中1％的更快（2个参数，发布）

optional parameters with strings: 18 % slower (2 parameters, release)
optional parameters with ints: <1 % faster (2 parameters, release)

的（也许编译器优化或会优化未来的可选参数调用？）的

(And maybe compilers optimize or will optimize those optional parameter calls in future ?)

答

我只是做了一个快速的测试和编译器优化代码。这个基本的例子主要方法。

I just did a quick test and the compiler optimizes the code. This basic example Main method.

public static void OptionalParamMethod(bool input, string input2 = null)
{
}

public static void Main(string[] args)
{
    OptionalParamMethod(true);
    OptionalParamMethod(false, "hello");
}

编译该所以可选PARAMS是由编译器填充。

Compiles to this so the optional params are filled in by the compiler.

public static void Main(string[] args)
{
    OptionalParamMethod(true, null);
    OptionalParamMethod(false, "hello");
}

至于性能，你可以争辩可选参数有微弱的优势，因为只有一个方法调用，而不是链接的方法调用就像你通常有一个重载的方法。下面的代码被编译输出显示什么我谈论。该差异是相当的学术，虽然我怀疑你会在实践中注意到。

As for performance you could argue optional parameters have a slight advantage as there is only a single method call rather than chained method calls like you would normally have for an overloaded method. The code below is compiled output to show what I am talking about. The difference is quite academic though and I doubt you would ever notice in practice.

public static void Main(string[] args)
{
    OptionalParamMethod(true, null);
    OptionalParamMethod(false, "hello");
    OverloadParamMethod(true);
    OverloadParamMethod(false, "hello");
}

public static void OptionalParamMethod(bool input, [Optional, DefaultParameterValue(null)] string input2)
{
    Console.WriteLine("OptionalParamMethod");
}

public static void OverloadParamMethod(bool input)
{
    OverloadParamMethod(input, null);
}

public static void OverloadParamMethod(bool input, string input2)
{
    Console.WriteLine("OverloadParamMethod");
}

超载或可选参数之间的性能差异？

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