CounterGrain_StartTimer.cs

public async Task StartCounterTimer()
{
    if (this.timer != null)
        throw new Exception("Can't start: already started");

    await this.Dispatch(new StartCounterAction());
    await this.WriteStateAsync();

    this.timer = this.RegisterTimer(async (state) => {
        var action = new IncrementCounterAction();
        // This sends the action to the clients for processing there
        // This processes the action here on the server, and also sends the syncstate to make sure the outcome is the same
        // The order of events is important here
        await this.Dispatch(action);
        await this.WriteStateAsync();

        await this.actionsToClientStream.OnNextAsync(action);

    }, null, TimeSpan.FromSeconds(3), TimeSpan.FromSeconds(3));

    await this.actionsToClientStream.OnNextAsync(new CounterStartedAction());
}