异步方法链式调用优化：Bar函数是否需保留async/await？

Great question! Let's break this down clearly, step by step:

Short answer: No, it's not necessary if Bar is just a pass-through that calls Foo and returns its result without modifying the data or adding extra logic. Directly returning the Task created by Foo is cleaner and more efficient.

Here's a side-by-side comparison to make it concrete:

// Redundant use of async/await
public async Task<MyData> Bar()
{
    return await Foo();
}

// Optimal approach
public Task<MyData> Bar()
{
    return Foo();
}

Yes, direct return is slightly more performant. When you use async/await unnecessarily, the compiler generates extra state machine code to track the asynchronous flow. This adds tiny overhead (state machine allocation, context switching checks) that's negligible in most cases, but can add up in high-throughput scenarios.

As for blocking: Neither approach blocks the calling thread (both are fully asynchronous). The difference is that the async/await version adds an extra layer of task wrapping, while the direct return just passes through the original task from Foo. No extra blocking occurs either way—you're just cutting out unnecessary work.

Let's break down both scenarios:

• Direct return: When you return Foo()'s task, you're passing the exact same task reference to Bar's caller. When the caller awaits this task, they're directly waiting for Foo's internal asynchronous operation to complete. No extra task or state machine is created.
• Async/await wrapper: The compiler transforms Bar into a state machine that does three things: calls Foo() to get a task, registers a callback to run when that task finishes, and returns a new "wrapper" task to the caller. When Foo's task completes, the callback triggers, and the wrapper task is marked as completed. This is a valid pattern if you need to add logic (like error handling), but useless for a simple pass-through.

One exception: You do need async/await if you want to add logic like exception handling or post-processing. For example:

public async Task<MyData> Bar()
{
    try
    {
        var result = await Foo();
        // Add extra logic here, like logging
        _logger.LogInformation("Foo completed successfully");
        return result;
    }
    catch (FooException ex)
    {
        // Custom error handling
        throw new BarException("Failed to fetch data", ex);
    }
}

内容的提问来源于stack exchange，提问作者Mo09890