Creating methods with infinite parameters?

问题:

In C# you can do this:

foo = string.Format("{0} {1} {2} {3} ...", "aa", "bb", "cc" ...);

This method Format() accepts infinite parameters, being the first one how the string should be formatted and the rest are values to be put in the string.

Today I've come to a situation where I had to get a set of strings and test them, then I remembered this language functionality, but I had no clue. After a few unsuccessful web searches, I've realised it would be more prudent to just get an array, which didn't make me quite satisfied.

Q: How do I make a function that accepts infinite parameters? And how do I use it ?

回答1:

With the params keyword.

Here is an example:

    public int SumThemAll(params int[] numbers)
    {
        return numbers.Sum();
    }

    public void SumThemAllAndPrintInString(string s, params int[] numbers)
    {
        Console.WriteLine(string.Format(s, SumThemAll(numbers)));
    }

    public void MyFunction()
    {
        int result = SumThemAll(2, 3, 4, 42);
        SumThemAllAndPrintInString("The result is: {0}", 1, 2, 3);
    }

The code shows various things. First of all the argument with the params keyword must always be last (and there can be only one per function). Furthermore, you can call a function that takes a params argument in two ways. The first way is illustrated in the first line of MyFunction where each number is added as a single argument. However, it can also be called with an array as is illustrated in SumThemAllAndPrintInString which calls SumThemAll with the int[] called numbers.

回答2:

Use the params keyword. Usage:

public void DoSomething(int someValue, params string[] values)
{
    foreach (string value in values)
        Console.WriteLine(value);
}

The parameter that uses the params keyword always comes at the end.

回答3:

A few notes.

Params needs to be marked on an array type, like string[] or object[].

The parameter marked w/ params has to be the last argument of your method. Foo(string input1, object[] items) for example.

回答4:

use the params keyword. For example

static void Main(params string[] args)
{
    foreach (string arg in args)
    {
        Console.WriteLine(arg);
    }
}

回答5:

You can achieve this by using the params keyword.

Little example:

public void AddItems(params string[] items)
{
     foreach (string item in items)
     { 
         // Do Your Magic
     }
}

回答6:

    public static void TestStrings(params string[] stringsList)
    {
        foreach (string s in stringsList){ } 
            // your logic here
    }

回答7:

 public string Format(params string[] value)
 {
            // implementation
 }

The params keyword is used

回答8:

function void MyFunction(string format, params object[] parameters) {

}

Instad of object[] you can use any type your like. The params argument always has to be the last in the line.