C#_parameter array

Sometimes we want the number of parameters to be variable.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            string fullName;

            fullName = Combine(Directory.GetCurrentDirectory(), "bin", "config", "index.html");

            Console.WriteLine(fullName);

            fullName = Combine(Environment.SystemDirectory, "Temp", "index.html");

            Console.WriteLine(fullName);

            fullName = Combine(new string[] { "C:\\", "Data", "HomeDir", "index.html" });

            Console.WriteLine(fullName);

            Console.ReadKey();
        }

        static string Combine(params string[] paths)
        {
            string result = string.Empty;
            foreach (string path in paths)
            {
                result = Path.Combine(result, path);
            }
            return result;
        }
    }
}

//D:\C#\ConsoleApp1\ConsoleApp1\bin\Debug\bin\config\index.html
//C:\WINDOWS\system32\Temp\index.html
//C:\Data\HomeDir\index.html

*PathEx.Combine() is exactly equivalent to Path.Combine(), except that it can handle a variable number of parameters instead of only two.

The Combine method accepts a variable number of arguments, either comma-separated string arguments, or a single array of strings, the former being called the expanded form of the method call , and the latter being the normal form.

To achieve this effect, the Combine method needs to:

Add the params keyword before the last parameter of the method declaration
Declare the last parameter as an array

The parameter array should pay attention to the following points:

The parameter array does not have to be the only parameter of the method , but must be the last. Since it can only be placed at the end, there can only be at most one parameter array.
The caller may specify zero actual parameters corresponding to the parameter array , which causes the passed parameter array to contain zero data items.
Parameter arrays are type-safe - the type of the actual parameter must be compatible with the type of the parameter array.
Instead of passing a comma-separated list of parameters, the caller can pass an actual array. The final generated CIL code is the same.
If the implementation of the target method requires a minimum number of parameters, please explicitly specify the parameters that must be provided in the method declaration. This way, omission of a required parameter results in an error from the compiler, without having to rely on runtime error handling. For example, using int Max(int first,params int[] operands) instead of int Max(params int[] operands) ensures that at least one integer argument is passed to Max.

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