using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

    var contents = new List<SomeObject> {

        new SomeObject { ParentId = 1, ControlName = "Id", ValueString = "aa" } ,

        new SomeObject { ParentId = 1, ControlName = "Location Res", ValueString = "bbb" } ,

        new SomeObject { ParentId = 1, ControlName = "Equipment Or Device Res", ValueString = "" } ,

        new SomeObject { ParentId = 1, ControlName = "Prep Notes", ValueString = "ccc" } ,

        new SomeObject { ParentId = 3, ControlName = "Location Res", ValueString = "" },

        new SomeObject { ParentId = 3, ControlName = "Equipment Or Device Res", ValueString = "" },

        new SomeObject { ParentId = 3, ControlName = "Prep Notes", ValueString = "" },

    };

    var badEntries = new List<SomeObject>();

    for (int i = contents.Count- 1; i >= 0; i--)

    {

         var dto = contents[i];

         if (dto.ControlName == "Location Res" || dto.ControlName == "Equipment Or Device Res" || dto.ControlName == "Prep Notes")

         {

             if (string.IsNullOrEmpty(dto.ValueString))

             {

                 Console.WriteLine(dto.ControlName);

                 badEntries.Add(dto);

             }

             else

             {

                 break;

             }

         }

    }

        Console.WriteLine("badentries " + badEntries.Count());

        var validRows = contents.Where(x => !(badEntries.Any(y => y.ParentId == x.ParentId))).ToList();

        Console.WriteLine("validRows " + validRows.Count());

        foreach(var row in validRows){

            Console.WriteLine(row.ValueString);

        }

    }

}

​

public class SomeObject

{

​

    public int ParentId { get; set; }

    public string ControlName {get;set;}

    public string ValueString { get; set; }

​

}