Is this expected C# 4.0 Tuple equality behavior?

I'm seeing different behavior between using .Equals and == between two of .NET 4.0's new Tuple<> instances. If I have overridden Equals on the object in the Tuple<> and call .Equals on the Tuples the override of Equals will be called. If I use == on the Tuples the override of Equals is not called. Is that by design and does it make sense?

EDIT: From answers and comments I can tell I'm not being clear. I know Tuple<> is a reference type and that for reference types == will check identity (ReferenceEquals). But, should Tuple<> override == to check equality of the objects it contains? For consistency, probably not.

For example if I have a simple object

public class NameAndNumber
{
    public int Number { get; set; }
    public string Name { get; set; }

    public override bool Equals(object obj)
    {
        if (obj is NameAndNumber)
        {
            NameAndNumber other = (NameAndNumber)obj;
            return Number == other.Number && Name == other.Name;
        }

        return false;
    }
}

and then I do something like this:

Tuple<NameAndNumber, NameAndNumber> left = new Tuple<NameAndNumber, NameAndNumber>(
      new NameAndNumber { Name = "one", Number = 1 }, 
      new NameAndNumber { Name = "two", Number = 2 });
Tuple<NameAndNumber, NameAndNumber> right = new Tuple<NameAndNumber, NameAndNumber>(
      new NameAndNumber { Name = "one", Number = 1 }, 
      new NameAndNumber { Name = "two", Number = 2 });
bool operatorResult = left == right;
bool equalsResult = left.Equals(right);
Console.Out.WriteLine("operatorResult = {0}  equalsResult = {1}", 
        operatorResult, equalsResult);

I get operatorResult = false equalsResult = true

Should I be expecting that?

I know the implementation of Equals on NameAndNumber isn't "right" it's just simplified sample code.

I have also tried implemen

.net-4.0 c#-4.0 tuples

Edit Report

By default, == (on a class) means reference equality; i.e. are they the same instance; what object.ReferenceEquals(x,y) would return.

You can provide your own == / != operators to get the expected behaviour - and when you override Equals it is important to override GetHashCode too (otherwise you break usage as a key - Why is it important to override GetHashCode when Equals method is overriden in C#?):

public static bool operator == (NameAndNumber x, NameAndNumber y) {
    if (x == null && y == null) return true;
    if (x == null || y == null) return false;
    return x.Number == y.Number && x.Name == y.Name;
    // or if polymorphism is important: return x.Equals(y);
}
public static bool operator !=(NameAndNumber x, NameAndNumber y) {
    return !(x == y); // lazy but works
}
public override int GetHashCode() {
    return (Name == null ? 0 : Name.GetHashCode()) +
        17 * Number.GetHashCode();
}

answered 2009-09-27T08:06:25.750

Is this expected C# 4.0 Tuple equality behavior?

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