using System.Collections.Generic;
public static void Main()
List<string>[] col = new List<string>[]
new List<string>(){"aaa", "bbb"},
new List<string>(){"a", "b", "d"},
new List<string>(){"xy","sl","yy","aq"}
var ordered = col.OrderBy(x => x[0].Length).ToList();
foreach (var list in ordered)
Console.WriteLine(string.Join(", ", list));