In C, a task represents an asynchronous operation. It is commonly used to encapsulate time-consuming and asynchronous operations such as reading data from a file or executing a database query.

Properties of a Task

• Status: Indicates the current state of the task (e.g., running, completed, canceled).
• Result: Contains the result of the asynchronous operation (if successfully completed).
• Exception: If the asynchronous operation encounters an exception, it is stored here.
• IsCompleted: Returns true if the task has completed (either successfully or with an exception).
• IsFaulted: Returns true if the task completed with an exception.

Creating Tasks

There are several ways to create tasks in C:

1. Task.Run(): Creates a task from a delegate or lambda expression.
2. Task.Factory.StartNew(): Similar to Task.Run(), but provides more control over task creation.
3. async/await: Asynchronous programming model that simplifies task creation and handling.

Consuming Tasks

Once a task has been created, it can be consumed using various methods:

• Task.Wait() and Task.Result: Blocks the calling thread until the task completes and returns the result.
• Task.ContinueWith(): Creates a continuation task that executes when the original task completes.
• await: Asynchronous programming model that avoids blocking the calling thread.

Cancellation and Faults

Tasks support cancellation and error handling:

• Cancellation: A task can be canceled, which will stop its execution and result in a 'canceled' status.
• Faults: If an asynchronous operation encounters an exception, the task will be marked as 'faulted' and the exception will be stored in the Exception property.

Benefits of Using Tasks

• Asynchronicity: Allows long-running operations to be performed without blocking the calling thread.
• Concurrency: Enables simultaneous execution of multiple tasks, improving application performance.
• Error Handling: Provides a structured way to handle exceptions in asynchronous operations.
• Composition: Tasks can be combined using continuation tasks to create complex workflows.

Conclusion

Tasks are a powerful tool in C for representing and managing asynchronous operations. They enable developers to create efficient and responsive applications that can perform time-consuming tasks without blocking the UI or other critical processes.

如何正确理解.NET 4.5和C#5.0中的async/await异步编程模式

相对于之前Begin/End模式和事件模式，async/await模式让程序员得以用同步的代码结构进行异步编程。async/await入门很方便，但是深入理解却涉及很多领域，如线程池、同步上下文等等。我断断续续接触了几个月，稍微有一些心得：

await的作用是等待异步Task完成，并不是阻塞的。举个例子，一个异步方法：