I’m currently working on VFS, a virtual file system. For running transfers, VFS internally maintains locks that do have expiration time. Accordingly, I found myself in need for a job scheduling mechanism in order to properly release expired locks. I looked around for a few alternatives, but eventually ended up writing my own lightweight version.

Features:

• Simple scheduling and callback mechanisms
• Silverlight compatible
• Lightweight
• Fluent API
• Detection of system time changes with optional rescheduling
• Optional forwarding of exceptions during job execution
• Open Source (Ms-PL)

Download library and sample

Current Version: 1.0.2, 2010.01.12

What Does it Do?

Basically, the library allows you to create a job, and submit that job to a scheduler, along with a callback action. This callback action is invoked as soon (or every time) the job is due.

Before going into the details, here’s a first code snippet that creates a simple Job that is supposed to run repeatedly (every 1.5 seconds) for a minute. Once the job is created, it is submitted to a Scheduler instance which processes the job and makes sure the submitted callback action is being invoked every time the job is due:

private Scheduler scheduler = new Scheduler();

public void RunOnce()
{
  //define a start / end time
  DateTime startTime = DateTime.Now.AddSeconds(5);
  DateTime endTime   = startTime.AddSeconds(60);

  //configure the job
  Job consoleJob = new Job();
  consoleJob.Run.From(startTime)
                .Every.Seconds(1.5)
                .Until(endTime);

  //submit the job with the callback to be invoked
  scheduler.SubmitJob(consoleJob, j => Console.Out.WriteLine("hello world"));
}

Silverlight

The project provides class libraries for .NET 3.5 and Silverlight 3, along with a Silverlight sample application that shows how to add scheduling functionality to your SL application with just a few lines of code.

While long-term scheduling isn’t probably something you need to do in a Silverlight application, the scheduler simplifies the management of periodic jobs, such as polling a server for updates. Below is a snippet from the Silverlight sample application. This job starts immediately, and runs indefinitely with an interval of 2 seconds:

private void CreateJob2()
{
  //create job
  Job<int> job = new Job<int>("Job 2");
  job.Data = 0;
  job.Run.Every.Seconds(2);

  //submit to scheduler
  scheduler.SubmitJob(job, LogJobExecution);
}


private void LogJobExecution(Job<int> job, int data)
{
  //updates user interface
}

Jobs

A job is a simple configuration item for the scheduler. There’s two built-in job types: Job and Job<T>. The only difference between the two is that the latter provides a Data property which allows you to attach state information directly to the job and have it delivered back to you when the job runs.

Read more…

I’ve been working on a new project of mine for a while now, and opened the project at CodePlex: VFS, the Virtual File System, is basically an abstraction to arbitrary hierarchical resources, which can be handled like a file system.

VFS comes with a set of file system providers and clients (including Silverlight support), and allows you to easily write your own providers (e.g. to expose the contents of a ZIP file on a remote server). Additional offerings are flexible security (e.g. to access your Azure blobs via VFS in order to plug-in a custom authorization scheme), auditing and reliable file transfers.

VFS is currently in early Alpha, but I’m working full steam ahead. Comments and wish lists are appreciated! For a more detailed introduction and a few code snippets, visit the project home:
http://vfs.codeplex.com