c# List.Contains() Method Returns False

Question

In the code block below I would expect dictCars to contain: { Chevy:Camaro, Dodge:Charger }

But, dictCars comes back empty. Because this line returns false each time it

Answer 1

You need to tell Contains what makes two Cars equal. By default it will use ReferenceEquals which will only call two objects equal if they are the same instance.

Either override Equals and GetHashCode in your Car class or define an IEqualityComparer class and pass that to Contains.

If two Cars that have the same CarID are "equal" then the implementation is pretty straightforward:

public override bool Equals(object o)
{
   if(o.GetType() != typeof(Car))
     return false;

   return (this.CarID == ((Car)o).CarID);
}

public override int GetHashCode()
{
  return CarID.GetHashCode();
}