How to successfully hash System.Windows.Input.Key values with modifier key states?

Question

I am trying to write a hashing algorithm that's gonna successfully hash System.Windows.Input.Key values with modifier key states, for instance:

ctrl = false
shift = true
alt = false
capslock = true
numlock = false
scroll lock = false
key: A

So a key value like this should be separated from others with different states for ctrl, shift, alt, etc. But since these are just true or false, I am not sure how to make it distinct for the hash values?

Any ideas? It just have to be unique enough to handle all possible key combinations.

Answer 1

I would build a class containing all values able to compute it's own hash code, like:

    class KeyInfo : IEquatable<KeyInfo>
    {
        public bool Ctrl { get; private set; }
        public bool Shift { get; private set; }
        public bool Alt { get; private set; }
        public bool CapsLock { get; private set; }
        public bool NumLock { get; private set; }
        public bool ScrollLock { get; private set; }
        public Keys Key { get; private set; }

        public KeyInfo(bool ctrl, bool shift, bool alt, bool capsLock, bool numLock, bool scrollLock, Keys key)
        {
            this.Ctrl = ctrl;
            this.Shift = shift;
            this.Alt = alt;
            this.CapsLock = capsLock;
            this.NumLock = numLock;
            this.ScrollLock = scrollLock;
            this.Key = key;
        }

        public override bool Equals(object obj)
        {
            return this.Equals(obj as KeyInfo);
        }

        public bool Equals(KeyInfo other)
        {
            if (other == null)
                return false;
            return this.Ctrl == other.Ctrl && this.Shift == other.Shift &&
                   this.Alt == other.Alt && this.CapsLock == other.CapsLock &&
                   this.NumLock == other.NumLock && this.ScrollLock == other.ScrollLock &&
                   this.Key == other.Key;
        }

        public override int GetHashCode()
        {
            unchecked
            {
                int hash = 17;
                hash = hash * 23 + this.Ctrl.GetHashCode();
                hash = hash * 23 + this.Shift.GetHashCode();
                hash = hash * 23 + this.Alt.GetHashCode();
                hash = hash * 23 + this.CapsLock.GetHashCode();
                hash = hash * 23 + this.NumLock.GetHashCode();
                hash = hash * 23 + this.ScrollLock.GetHashCode();
                hash = hash * 23 + this.Key.GetHashCode();
                return hash;
            }
        }
    }

Credits to this Jon Skeet's answer for the GetHashCode() implementation.

N.B.

this class can be effectively used as a Dictionary key, into HashSet or in LINQ Distinct() and other LINQ sets' operations.

EDIT:

I'd like to enforce the fact that you mustn't use the hash code as dictionary key, but use the whole class instead.
You cannot rely on the uniqueness of the hash-codes because hashing it's subjected to collisions.