using System;

using System.Linq;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        var items = new [] {

            new { Name = "設定1", Value = 100},

            new { Name = "設定2", Value = 200},

            new { Name = "設定3", Value = 300},

            new { Name = "設定4", Value = 400},

            new { Name = "設定5", Value = 500}

        };

        var regex = new Regex(@"設定(?<num>\d+)", RegexOptions.IgnoreCase | RegexOptions.Singleline);

        var idx = 1;

        var result = items

            .Select(item => new { m = regex.Match(item.Name), item.Name })

            .Where(x => x.m.Success == true)

            .OrderBy(x => int.Parse(x.m.Groups["num"].Value))

            .Select(x => int.Parse(x.m.Groups["num"].Value));

        if (result.ToArray().Count() > 0) idx = result.Max() + 1;

        Console.WriteLine(idx);

    }

}