Question

I want to implement a sort logic as: Set Washington as first if exists.
The following code works good.However,I’m not caring about cities not equals “Washington” and wondering why I need return -1 and could not return 0(meaning “equals” in IComparable)?

P.S. I have tried it, “Chicago” will be first if return 0.

class Program
{
    static void Main(string[] args)
    {
        List<City> cityList  = new List<City>() 
        { 
            new City(){Name = "New York"},
            new City(){Name ="Los Angeles"},
            new City(){Name="Washington"},
            new City(){Name="Chicago"}
        };
        cityList.Sort();
    }
}

public class City: IComparable
{
    public string Name { get; set; }

    public int CompareTo(object obj)
    {
        if ((obj as City).Name == "Washington")
        {
            return 1;
        }
        else 
        {
            return -1;
        }
    }
}

Answer 1

Returning 0 means the string are equal.

If you return 0 whenever obj is not “Washington”, sometimes “Washington” will be in the current instance you are comparing obj with. This will prevent Washington rising to the top.