Question

I have an existing table and a new table.
The tables contain at least two items that need to be checked.
I need to do the following items

1) Get a list of items that are not in the new table but are in the existing table. – So they can be removed
2) Get a list of items that are in the new table but not in the existing table – So they can be added

3) Get a list of items that are in both tables but the existing table needs updateing

Here is the data

var existingItems = new[] 
{ 
    new RetryItem { CellId = 1, Content = "Bob" }, 
    new RetryItem { CellId = 2, Content = "Bill" }, 
    new RetryItem { CellId = 3, Content = "Frank" }, 
    new RetryItem { CellId = 4, Content = "Tom" }, 
    new RetryItem { CellId = 5, Content = "Dick" }, 
    new RetryItem { CellId = 6, Content = "Harry" }, 
}; 

var newItemsLarger = new[] 
{ 
    new RetryItem { CellId = 1, Content = "Bob" }, 
    new RetryItem { CellId = 2, Content = "Bill" }, 
    new RetryItem { CellId = 3, Content = "Frank" }, 
    new RetryItem { CellId = 4, Content = "Tom now Thoams" }, 
    new RetryItem { CellId = 5, Content = "Dick now Dicky" }, 
    new RetryItem { CellId = 6, Content = "Harry Now Harriet" }, 
    new RetryItem { CellId = 7, Content = "Mary" }, 
    new RetryItem { CellId = 8, Content = "Mungo" }, 
    new RetryItem { CellId = 9, Content = "Midge" }, 
};

Answer 1

You can use the following sample program in a console application:

using System.Linq;

namespace ExperimentConsoleApp
{
    class Program
    {
        static void Main()
        {
            // Check if the item is in existingItems but not in newItems
            var itemsToBeRemoved = (from e in existingItems
                                    where !newItemsLarger.Any(n => n.CellId == e.CellId)
                                    select e).ToList();

            // Check if the item is in newItems but not in existingItems 
            var itemsToBeAdded = (from n in newItemsLarger
                                  where !existingItems.Any(e => n.CellId == e.CellId)
                                  select n).ToList();

            // Match the items on Id and check if their contents equals
            var itemsToBeUpdated = (from e in existingItems
                                    from n in newItemsLarger
                                    where e.CellId == n.CellId && e.Content != n.Content
                                    select n).ToList();
        }

        static RetryItem[] existingItems = new[] 
                        { 
                            new RetryItem { CellId = 1, Content = "Bob" }, 
                            new RetryItem { CellId = 2, Content = "Bill" }, 
                            new RetryItem { CellId = 3, Content = "Frank" }, 
                            new RetryItem { CellId = 4, Content = "Tom" }, 
                            new RetryItem { CellId = 5, Content = "Dick" }, 
                            new RetryItem { CellId = 6, Content = "Harry" }, 
                        };

        static RetryItem[] newItemsLarger = new[] 
                        { 
                            new RetryItem { CellId = 1, Content = "Bob" }, 
                            new RetryItem { CellId = 3, Content = "Frank" }, 
                            new RetryItem { CellId = 4, Content = "Tom now Thoams" }, 
                            new RetryItem { CellId = 5, Content = "Dick now Dicky" }, 
                            new RetryItem { CellId = 6, Content = "Harry Now Harriet" }, 
                            new RetryItem { CellId = 7, Content = "Mary" }, 
                            new RetryItem { CellId = 8, Content = "Mungo" }, 
                            new RetryItem { CellId = 9, Content = "Midge" }, 
                        };
    }

    public class RetryItem
    {
        public int CellId { get; set; }
        public string Content { get; set; }
    }
}