using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		string pattern = @"(?<=\bInitValue\([^()]*)[^, ]+(?=[^()]*\))";
        string str = "InitValue(Input1, Input2, Input3)";            
        foreach (Match m in Regex.Matches(str, pattern))
        {
            Console.WriteLine(m.Value);
        }
	}
}