using System;
using System.Text.RegularExpressions;
 
public class Test
{
    public static void Main()
    {
        Regex rx = new Regex("^([A-Z]+[1-9][0-9]*(:[A-Z]+[1-9][0-9]*)?($|,(?!$)))*$");
        Console.WriteLine(rx.IsMatch("C5:H6"));
        Console.WriteLine(rx.IsMatch("C5"));
        Console.WriteLine(rx.IsMatch("C5:H6,J5:P6,R5:DM6,C15"));
        Console.WriteLine(rx.IsMatch("C5:H6,J5:P6,R5:DM6,C15,"));
        Console.WriteLine(rx.IsMatch("C5:H6J5:P6,R5:DM6,C15"));
        Console.WriteLine(rx.IsMatch(",C5:H6:J5:P6,R5:DM6,C15"));
    }
}

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