How Can SemaphoreSlim Limit Concurrent Task Execution in .NET?

Using Tasks to Limit Concurrent Execution in Parallel Tasks

In many scenarios, it becomes necessary to restrict the number of tasks executing simultaneously in parallel processing. This is especially true when resource limitations exist or when excessive concurrency can lead to performance degradation.

To address this challenge, .NET provides a variety of options for managing task concurrency. One popular approach involves utilizing the Task Parallel Library (TPL) and the SemaphoreSlim class.

For instance, consider a scenario where you have a set of 100 tasks that each take approximately 10 seconds to complete. You wish to limit the execution to only 10 tasks at any given time.

To achieve this using Tasks:

• Create a SemaphoreSlim instance: Create a SemaphoreSlim object, passing the maximum number of concurrent tasks as the argument (in this case, 10).
• Wrap task creation in a loop: Initiate a loop for 115 iterations (100 tasks 15 to allow for potential delays).
• Acquire semaphore before task creation: Inside the loop, call Wait() on the semaphore to acquire a permit, ensuring that no more than 10 tasks are executing concurrently.
• Create a new task: Use Task.Factory.StartNew to create a new task. Specify TaskCreationOptions.LongRunning to indicate that the task will potentially take a long time to complete.
• Release semaphore after task completion: Once the task is completed, continue the task with ContinueWith and call Release on the semaphore to release the acquired permit, allowing another task to begin execution.

By implementing this approach, you can effectively limit the number of tasks running concurrently, ensuring a controlled and resource-efficient execution of tasks in your application.

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