Func的例外未捕获（异步） [英] Exception from Func<> not caught (async)

问题描述

我有以下一段代码（为了进行此复制而进行了简化）。显然，catch异常块将包含更多逻辑。

I'm having the following piece of code (simplified in order to make this repro). Obviously, the catch exception block will contain more logic.

我有以下代码：

void Main()
{
    var result = ExecuteAction(async() =>
        {
            // Will contain real async code in production
            throw new ApplicationException("Triggered exception");
        }
    );
}

public virtual TResult ExecuteAction<TResult>(Func<TResult> func, object state = null)
{
    try
    {
        return func();
    }
    catch (Exception ex)
    {
        // This part is never executed !
        Console.WriteLine($"Exception caught with error {ex.Message}");
        return default(TResult);
    }
}

为什么从未执行catch异常块？

Why is the catch exception block never executed?

推荐答案

未抛出异常，因为func的实际签名是 Funk< Task> 由于该方法是异步的。

The exception is not thrown because the actual signature of func is Funk<Task> due to the method being async.

异步方法具有特殊的错误处理，只有在您等待该函数后才会引发异常。如果要支持异步方法，则需要具有第二个可以处理异步委托的函数。

Async methods have special error handling, the exception is not raised until you await the function. If you want to support async methods you need to have a 2nd function that can handle async delegates.

void Main()
{
    //This var will be a Task<TResult>
    var resultTask = ExecuteActionAsync(async() => //This will likely not compile because there 
                                                   // is no return type for TResult to be.
        {
            // Will contain real async code in production
            throw new ApplicationException("Triggered exception");
        }
    );
    //I am only using .Result here becuse we are in Main(), 
    // if this had been any other function I would have used await.
    var result = resultTask.Result; 
}

public virtual async TResult ExecuteActionAsync<TResult>(Func<Task<TResult>> func, object state = null)
{
    try
    {
        return await func().ConfigureAwait(false); //Now func will raise the exception.
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Exception caught with error {ex.Message}");
        return default(TResult);
    }
}

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