Extension methods example

Ya.cs

namespace SampleNS
{
public static class CommonUtil
{
    public static string ListToString(this IList list)
    {
        StringBuilder result = new StringBuilder("");
        
        if (list.Count > 0)
        {
            result.Append(list[0].ToString());
            for (int i = 1; i < list.Count; i++)
                result.AppendFormat(", {0}", list[i].ToString());                
        }
        return result.ToString();
    }
}
}