Question

How do you search a generic collection to see if an object’s properties are equal?

List<Customer> = customers = GetCustomers();

Customer c = new Customer() { FirstName = "Sam" };

customers.Contains(c); //doesn't work

Answer 1

You need to define “equality” for the object. You can do this several ways.

1. Override the Equals method of Customer itself, so that it uses what you think of as equality.
2. Define a custom comparer, which implements IEqualityComparer that you can pass into contains. Do this if you need to use different definitions of “equality” at different times, or if you don’t have the ability to modify the type.

Note that any time you override Equals for a type it’s important to also override GetHashCode, and vice versa. It’s important to ensure that any objects that are considered equal by the definition of Equals also have the same hash code. It won’t matter in this particular case, but it will matter when using a hash based data structure.