异步异常未被捕获

Question

我有一个引用以下代码的Windows服务.使用下面的方法,我的代码包含一个try..catch块,但它似乎并没有catch RefereshTokenException认为是thrown在下面的方法.显然我的理解async是不正确的.

private async void RefreshTokens()
{
    try
    {
        var cognito = new CognitoApi();
        var response = cognito.TokenRefresh(_refreshToken);

        if (response.HttpStatusCode == HttpStatusCode.OK)
        {
            _idToken = new AwsToken(response.AuthenticationResult.IdToken);
            _accessToken = new AwsToken(response.AuthenticationResult.AccessToken);
        }
        else
        {
            await _signIn(_credentials.SiteId, _credentials.LocationId, null);
        }
    }
    catch (NotAuthorizedException)
    {
        await _signIn(_credentials.SiteId, _credentials.LocationId, null);
    }
    catch (Exception ex)
    {
        throw new RefreshTokenException("Failed refreshing tokens.", ex);
    }
}

这是调用的代码 RefreshTokens

public async void Process(QueueMessage queueMessage, Action<QueueMessage> retryAction)
{
    _processingCounter.Increment();

    try
    {
        ......
        IAwsToken idToken = authenticationService.Tokens.IdToken; //This is the code that calls "RefreshTokens" method
        ........
    }
    catch (Exception ex)
    {
        //Code never reaches here...
        _logger.Error("Error in ProcessMessage", ex);
    }

    _processingCounter.Decrement();
}

Answer 1

这是一个async void.避免异步void方法的一个主要原因是您无法处理它们抛出的异常.

使它成为一个async Task和await它在呼叫者.

请注意,您在该调用者中遇到相同的问题, async void Process(...)

让它成为一个async Task好的并且一路向上.async/await应该形成一个链,从GUI或Controller到异步I/O调用.