Constructs a message that, when send to Replicator, will perform an update of a structure stored under provided key. Update operation is described by modify function, that will take a previous value as an input parameter. If no value was found under the key, an initial value will be used instead. An consistency level may be provided to set up certain constraints on retrieved IUpdateResponse replied from replicator as a result.

public static Update Update<T>(
	IKey<T> key,
	T initial,
	IWriteConsistency consistency,
	Func<T, T> modify
)
where T : IReplicatedData

static member Update : 
        key : IKey<'T> * 
        initial : 'T * 
        consistency : IWriteConsistency * 
        modify : Func<'T, 'T> -> Update  when 'T : IReplicatedData