String array sorted and grouped sample

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace gf_20171109_01 {
  class Program {

    static private Random random = new Random();

    static String[] randomStringArray(int arrayLength, int firstLetterRangeLength, int minLength, int lengthRangeLength) {
      if (arrayLength < 0) throw new ArgumentOutOfRangeException("arrayLength");
      if (firstLetterRangeLength < 1 || firstLetterRangeLength > 26) throw new ArgumentOutOfRangeException("firstLetterCount");
      if (minLength < 0) throw new ArgumentOutOfRangeException("minLength");
      if (lengthRangeLength < 0) throw new ArgumentOutOfRangeException("lengthRange");

      String[] retVal = new String[arrayLength];
      for (int i=0; i < arrayLength; i++) {
        StringBuilder sb = new StringBuilder(minLength + lengthRangeLength);
        Char firstLetter = (Char)random.Next(65,65+firstLetterRangeLength); // 'A' to another letter
        sb.Append(firstLetter);
        int length=random.Next(minLength, minLength + lengthRangeLength);
        for (int j=0; j<length; j++) {
          Char nextLetter=(Char) random.Next(97, 97 + 26);
          sb.Append(nextLetter);
        };
        retVal[i] = sb.ToString();
      };
      return retVal;
    }

    static void Main(string[] args) {
      String[] nameList = randomStringArray(8, 5, 3, 6);

      Console.WriteLine("Unsorted random names:");
      for (int i=0; i < nameList.Length; i++) {
        Console.WriteLine(nameList[i]);
      };
      Console.WriteLine();

      var nameListSortedAndGrouped=nameList
            .OrderBy((String s) => s)
            .GroupBy((String s) => s[0])
        ;
      Console.WriteLine("Sorted and grouped:");
      foreach (var a in nameListSortedAndGrouped) {
        Console.WriteLine("Names starting with " + a.Key.ToString() + ":");
        foreach (var b in a) {
          Console.WriteLine(b.ToString());
        };
      };

      Console.WriteLine(); Console.Write("Press any key to exit..."); Console.ReadKey();
    }
  }
}