C# Linq query to join two lists and assign the result to combobox

Question

I have a two list of strings

 Lista           Listb
 ------------------------
 apple           mango
 mango           grapes
 grapes          watermelon
 pineapple       orange
 banana

I want to show all the items of lista in my combobox also select items common to both in this case mango and grapes and pre-check them in the combobox

combobox items
---------------------
 apple
 mango - checked
 grapes - checked
 pineapple
 banana 

Answer 1

The following should give you a list containing value from Lista and additional information of whether an item in the list should be checked or not in IsChecked property :

var result = Lista.Select(a => new 
                    {
                        Value = a,
                        IsChecked = Listb.Any(b => b == a)
                    }).ToList();

The rest is simply binding the result to combobox. This step varies depending on your platform (ASP.NET, WPF, Windows Form, etc. almost all has combobox), and each, I believe, is well-documented on the internet so you should read and try one first.

Answer 2

you can do

var listA = new[] {"apple", "mango", "grapes", "pineapple", "banana"};
var listB = new[] {"mango", "grapes", "watermelon", "orange"};

var common = listA.Intersect(listB);

to get the overlap

Answer 3

Try Left join in Linq

var listA = new[] { "apple", "mango", "grapes", "pineapple", "banana" }.ToList();
var listB = new[] { "mango", "grapes", "watermelon", "orange" }.ToList();

var listCheckboxItem =
(
    from a in listA
    join b in listB on a equals b into lst
    from item in lst.DefaultIfEmpty()
    select new
    {
        Name = a,
        IsChecked = !(string.IsNullOrEmpty(item))
    }
).ToList();

Answer 4

Select can get a list of booleans showing which elements are in both lists.

List<string> Lista = new List<string>(new string[] { "apple", "mango", "grapes", "pineapple", "banana" });
List<string> Listb = new List<string>(new string[] {"mango","grapes","watermelon","orange"});

var inBoth = Lista.Select(x => Listb.Contains(x));
// False, True, True, False, False