// The LINQ Where can be used to filter in a collection.
// It will return a Enumerable that contains all of the matching elements

var names = new List<string>() {"John", "Jane", "William"};

//I use ToLower to get any name that contains a J, Capital or not.
var namesWithJ = names.Where(n => n.ToLower().Contains("j"));

//Returns IEnumerable<string> that contains ["John", "Jane"]

var queryLondonCustomers = from cust in customers
                           where cust.City == "London"
                           select cust;

var query = MemberTable.Where(x=>x.sex.Equals(Sex))

if (members != null)
     query = query.Where(x=>members.Contains(x.membercode))

//use your query
query.ToList();

var users = new List<Users>()
var names = users.Select(xx=> xx.Name);

dataSource.StateList.Where(s => countryCodes.Contains(s.CountryCode))

linq in c#