Decimal to roman numeral converter in c#

Csharp program for Decimal to roman numeral converter. Here mentioned other language solution.

// Include namespace system
using System; 
//  C# program for
//  Conversion from Decimal to roman number
public class Perform
{
    // Display roman value of n
    public static void result(int n)
    {
        switch (n)
         {
            // Test Cases
            case 1:
                Console.Write("I");
                break;
            case 4:
                Console.Write("IV");
                break;
            case 5:
                Console.Write("V");
                break;
            case 9:
                Console.Write("IX");
                break;
            case 10:
                Console.Write("X");
                break;
            case 40:
                Console.Write("XL");
                break;
            case 50:
                Console.Write("L");
                break;
            case 90:
                Console.Write("XC");
                break;
            case 100:
                Console.Write("C");
                break;
            case 400:
                Console.Write("CD");
                break;
            case 500:
                Console.Write("D");
                break;
            case 900:
                Console.Write("DM");
                break;
            case 1000:
                Console.Write("M");
                break;
        }
    }
    public static long select(long number, 
                               int[] collection, int size)
    {
        var n = 1;
        var i = 0;
        for (
        i = 0; i < size; ++i)
        {
            if (number >= collection[i])
            {
                n = collection[i];
            }
            else
            {
                break;
            }
        }
        result(n);
        // Reduce the value of number
        return number - n;
    }
    public static void romanNo(long number)
    {
        if (number <= 0)
        {
            // When is not a natural number
            return;
        }
        // Base case collection
        int[] collection =
        {1, 4, 5, 9, 10, 40, 50, 90, 100, 400, 500, 900, 1000};
        // Get the size of collection
        var size = collection.Length;
        Console.Write(" " + number + " : ");
        while (number > 0)
        {
            number = select(number, collection, size);
        }
        // Add new line
        Console.WriteLine();
    }
    public static void Main(String[] args)
    {
        // Test Case
        romanNo(10);
        romanNo(18);
        romanNo(189);
        romanNo(604);
        romanNo(982);
        romanNo(3000);
    }
}

Output

 10 : X
 18 : XVIII
 189 : CLXXXIX
 604 : DCIV
 982 : DMLXXXII
 3000 : MMM