Few months ago I wrote blog post about how to run code daily at specific time. I dint know that the post will be the most viewed post on my blog. Also there were several questions how to implement complete example. So today I have decided to write another post, and extend my previous post in order to answer thise question as well as to generalize this subject in to cool demo called Scheduler DEMO.

The post is presenting simple Windows Forms application which calls a method for every minute, day, week, month or year. Also demo shows how to cancel the scheduler at any time.

The picture above shows simple Windows Forms application with two  numeric control which you can set starting hour and minute for the scheduler. Next there is a button Start to activate timer for running code, as well as Cancel button to cancel the scheduler. When the time is come application writes the message on the Scheduler Log.

Implementation of the scheduler

Scheduler is started by clicking the Start button which is implemented with the following code:

/// <summary>
/// Setting up time for running the code
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void startBtn_Click(object sender, EventArgs e)
{

    //retrieve hour and minute from the form
    int hour = (int)numHours.Value;
    int minutes = (int)numMins.Value;

    //create next date which we need in order to run the code
    var dateNow = DateTime.Now;
    var date = new DateTime(dateNow.Year, dateNow.Month, dateNow.Day, hour, minutes, 0);

    listBox1.Items.Add("**********Scheduler has been started!*****");

    //get nex date the code need to run
    var nextDateValue=getNextDate(date,getScheduler());

    runCodeAt(nextDateValue, getScheduler());

}

When the time is defined then the runCodeAt method is called which implementation can be like the following;

/// <summary>
/// Determine the timeSpan Dalay must wait before run the code
/// </summary>
/// <param name="date"></param>
/// <param name="scheduler"></param>
private void runCodeAt(DateTime date,Scheduler scheduler )
{
    m_ctSource = new CancellationTokenSource();

    var dateNow = DateTime.Now;
    TimeSpan ts;
    if (date > dateNow)
        ts = date - dateNow;
    else
    {
        date = getNextDate(date, scheduler);
        ts = date - dateNow;
    }

    //enable the progressbar
    prepareControlForStart();

    //waits certan time and run the code, in meantime you can cancel the task at anty time
    Task.Delay(ts).ContinueWith((x) =>
        {
            //run the code at the time
                methodToCall(date);

                //setup call next day
                runCodeAt(getNextDate(date, scheduler), scheduler);

        },m_ctSource.Token);
}

The method above creates the cancelationToken needed for cancel the scheduler, calculate timeSpan – total waiting time, then when the time is come call the method methodToCall and calculate the next time for running the scheduler.

This demo also shows how to wait certain amount of time without blocking the UI thread.

The full demo code can be found on OneDrive.