using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    class TableRow 

    {

        public int I {get;set;}

        public bool CheckboxField {get;set;}

        TableRow(int i)

        {

            this.I = i;

            this.CheckboxField = (i % 3 == 0); //in our demo, assume that some are already checked, some aren't

        }

        public static IEnumerable<TableRow> GenerateTableRows(int howMany)

        {

            for (int i=0; i<howMany; i++)

            {

                yield return new TableRow(i);

            }

        }

    }

    public static void Main()

    {

        new Program();

        Console.WriteLine("Done");

    }

    Program() 

    {

        ICollection<TableRow> myTable = new List<TableRow>(TableRow.GenerateTableRows(12));

        while (myTable.Count(x => !x.CheckboxField) > 0) //keep looping until we've processed all records

        {

            var randomRecord = GetRandomRecord(myTable);

            Console.WriteLine(randomRecord == null ? "No Matching Rows Exist" : randomRecord.I.ToString()); 

        }

    }

    TableRow GetRandomRecord(ICollection<TableRow> myTable)

    {

        var rnd = new Random(); //we could optionally provide this as a parameter too to avoid recreating each time

        var randomRecord = myTable

            .Where(x => !x.CheckboxField)

            .ToList()

            .OrderBy(x => rnd.Next())

            .FirstOrDefault();  

        if(randomRecord != null) //avoid issue if all items are checked

        {

            randomRecord.CheckboxField = true; //mark this record as having been processed

        }

        return randomRecord;

    }

}