SyncHashSet is an easy way to keep a HashSet collection automatically synchronized over the network.

Callbacks for SyncHashSet are similar to SyncList. And like other synchronization types changes are set immediately before the callback occurs.

private readonly SyncHashSet<int> _myCollection = new SyncHashSet<int>();

private void Awake()
    _myCollection.OnChange += _myCollection_OnChange;

private void FixedUpdate()
    //You can modify a synchashset as you would any other hashset.

/* Like SyncVars the callback offers an asServer option
 * to indicate if the callback is occurring on the server
 * or the client. As SyncVars do, changes have already been
 * made to the collection before the callback occurs. */
private void _myCollection_OnChange(SyncHashSetOperation op, int item, bool asServer)
    switch (op)
        /* An object was added to the hashset. Item is
         * is the added object. */
        case SyncHashSetOperation.Add:
        /* An object has been removed from the hashset. Item
         * is the removed object. */
        case SyncHashSetOperation.Remove:
        /* The hashset has been cleared. 
         * Item will be default. */
        case SyncHashSetOperation.Clear:
        /* An entry in the hashset has been updated. 
         * When this occurs the item is removed
         * and added. Item will be the new value.
         * Item will likely need a custom comparer
         * for this to function properly. */
        case SyncHashSetOperation.Update:
        /* When complete calls all changes have been
        * made to the collection. You may use this
        * to refresh information in relation to
        * the changes, rather than doing so
        * after every entry change. All values are
        * default for this operation. */
        case SyncHashSetOperation.Complete:

If you are using this SyncType with a container, such as a class or structure, and want to modify values within that container, you must set the value dirty. See the example below.

private struct MyContainer
    public string PlayerName;
    public int Level;

private readonly SyncHashSet<MyContainer> _containers = new();
private MyContainer _containerReference = new();

private void Awake()
    _containerReference.Level = 5;

private void ModifyPlayer()
    //This will change the value locally but it will not synchronize to clients.
    _containerReference.Level = 10;
    //The value must be set dirty to force a synchronization.

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