c# add to list if not exist code example

Example 1: c# verify in class exist in list

Item wonderIfItsPresent = ...
bool containsItem = myList.Any(item => item.UniqueProperty == wonderIfItsPresent.UniqueProperty);'

Example 2: c# object is in object list

public class A { public int Id {get;set;} public A() {} public A(int id) {Id = id;}}

List<A> list = new List<A>() { new A() { Id = 1}, new A() { Id = 2}};

bool containsItem = list.Any(item => item.Id == 3);
// this would return false.