How Can I Execute Multiple Tasks Concurrently with a Limited Number of Threads Using C#?

Executing Tasks Concurrently with Limited Threads

Problem:

Suppose you have a set of tasks that must be executed sequentially, with only a maximum of X tasks running at a time. Traditionally, ThreadPool.QueueUserWorkItem() was used for such tasks, but it is now considered a suboptimal approach.

Solution Using Tasks:

To achieve this concurrency limitation using Tasks, we can employ a SemaphoreSlim object to manage the number of threads available. Here's a code snippet demonstrating the approach:

SemaphoreSlim maxThread = new SemaphoreSlim(10);

for (int i = 0; i < 115; i++)
{
    maxThread.Wait();
    Task.Factory.StartNew(() =>
        {
            // Your task implementation
        }, TaskCreationOptions.LongRunning)
    .ContinueWith((task) => maxThread.Release());
}

Here's how the code works:

• SemaphoreSlim Initialization: A SemaphoreSlim is initialized with a maximum thread count of 10, which allows up to 10 tasks to run concurrently.
• Task Execution: For each task to be executed, the Wait() method of the semaphore is called, which blocks until a thread becomes available. Once a thread is free, a new task is started using Task.Factory.StartNew().
• Task Completion: After each task completes, the ContinueWith() method attached to the task releases the thread used by calling the Release() method of the semaphore.
• Sequential Execution: Because of the limited thread availability enforced by the semaphore, tasks are executed sequentially, with a maximum of 10 tasks running at any given time.

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