I want to create a job with 5 tasks. The first task must be executed at the very beginning, next the second task and next all of the rest tasks, even parallelly..

How can I accomplish that with VisualCron .NET API?

If you look at the sample for creating Tasks in the .NET API you will see that if you call Job for NewTask() it will add the order value. This will make sure that Tasks run in order. On Job cannot be both run in order and in paralell. To achive what you want to you need to create two Jobs and set second Job to run in parallell. Then, Task 3 in first Job should be of type "Job/Task control Task" and call second Job.

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