----------
        public string Set(string sError)
        {
            return Set(enumZReturnNo.Fail, sError);
        }
        public string Set(string sFormat, params object[] poa)
        {
            return Set(string.Format(sFormat, poa));
        }

----------
        public void SetFail(string sMessage)
        {
            msMsg = sMessage;
            mbOK = false;
            mdTime = DateTime.Now;
        }
        public void SetFail(string sFormat, params object[] poa)
        {
            msMsg = string.Format(sFormat, poa);
            mbOK = false;
            mdTime = DateTime.Now;
        }

----------

see also: Method Parameters:
	params, ref, out

----------
code:

// cs_params.cs
using System;
public class MyClass 
{

    public static void UseParams(params int[] list) 
    {
        for (int i = 0 ; i < list.Length; i++)
        {
            Console.WriteLine(list[i]);
        }
        Console.WriteLine();
    }

    public static void UseParams2(params object[] list) 
    {
        for (int i = 0 ; i < list.Length; i++)
        {
            Console.WriteLine(list[i]);
        }
        Console.WriteLine();
    }

    static void Main() 
    {
        UseParams(1, 2, 3);
        UseParams2(1, 'a', "test"); 

        // An array of objects can also be passed, as long as
        // the array type matches the method being called.
        int[] myarray = new int[3] {10,11,12};
        UseParams(myarray);
    }
}

output:
1
2
3

1
a
test

10
11
12