如何从C＃中的同步调用异步方法？

Question

I am adding a new web API call to existing functionality. I want to make this API call async but looks like it is causing deadlock. I have to make a lot more changes if I want to make entire code channel async which is not possible.

Questions I have are:

1. Is it possible to call async method from regular method?

2. What am I missing here? OR What is the correct approach here?

Code:

// Exisitng Method
public Tuple<RestaurantDeliveryProvider, DeliveryHubResult, Task<DeliveryManagerQuoteResponse>> CreateDeliveryRequest(OrderContextDTO orderContextDto)
{
    var provider = RestaurantBl.GetDeliveryProviderInformationByRestaurantId(orderContextDto.RestaurantId ?? 0);

    var deliveryHubResult = RestaurantBl.GetDeliveryHubResult(orderContextDto.OrderId ?? 0);;

    // New Call which always comes back with "Not Yet Computed" result
    Task<DeliveryManagerQuoteResponse> deliveryManagerQuoteResponse = _deliveryManager.CreateQuoteRequestAsync(orderContextDto, orderInfo);

    return Tuple.Create(provider, deliveryHubResult, deliveryManagerQuoteResponse);
}

Async Methods:

public async Task<DeliveryManagerQuoteResponse> CreateQuoteRequestAsync(OrderContextDTO orderContextDto, OrderInfoDTO orderInfo)
{
    DeliveryManagerQuoteResponse deliveryManagerQuoteResponse = null;

    try
    {
        var restaurantInfo = RestaurantApi.GetRestaurant(orderInfo.RestaurantId);
        var quoteRequest = new DeliveryManagerQuoteRequest
        {
            DeliveryProvider = null, 
            Country = orderContextDto.DeliveryEstimateRequestDto.RequestedDeliveryAddress.Country,
            Concept = "BK", 
            StoreName = "BK-TEST-US-4", 
            OrderId = orderInfo.OrderId.ToString(),
            AllowCash = false, 
            PaymentType = OrderPaymentType.Prepaid_Credit,
            Note = orderInfo.DeliveryInstructions,
        };

        deliveryManagerQuoteResponse = await Quote(quoteRequest);
    }
    catch (Exception ex)
    {
        Log.ErrorFormat("Get Delivery Manager Quote failed: Error: {0}, OrderId: {1}", ex.Message, orderContextDto.OrderId);
    }

    return deliveryManagerQuoteResponse;
}


public async Task<DeliveryManagerQuoteResponse> Quote(DeliveryManagerQuoteRequest quoteRequest)
{
    DeliveryManagerQuoteResponse deliveryManagerQuoteResponse;

    var client = HttpClientFactory.GetClient();
    var content = HttpClientFactory.JsonContentFactory.CreateJsonContent(quoteRequest);
    var response = await client.PostAsync("https://myUrl", content);

    if (response.IsSuccessStatusCode)
    {
        var data = await response.Content.ReadAsStringAsync();
        deliveryManagerQuoteResponse = JsonConvert.DeserializeObject<DeliveryManagerQuoteResponse>(data);
    }
    else
    {
        throw new Exception((int)response.StatusCode + "-" + response.StatusCode);
    }

    return deliveryManagerQuoteResponse;
}

I tried following as well but same result:

public async Task<DeliveryManagerQuoteResponse> Quote(DeliveryManagerQuoteRequest quoteRequest)
{
    DeliveryManagerQuoteResponse deliveryManagerQuoteResponse;

    using (var client = new HttpClient())
    {
        var content = HttpClientFactory.JsonContentFactory.CreateJsonContent(quoteRequest);
        var response = await client.PostAsync("https://myUrl", content);

        if (response.IsSuccessStatusCode)
        {
            var data = await response.Content.ReadAsStringAsync();
            deliveryManagerQuoteResponse = JsonConvert.DeserializeObject<DeliveryManagerQuoteResponse>(data);
        }
        else
        {
            throw new Exception((int)response.StatusCode + "-" + response.StatusCode);
        }
    }

    return deliveryManagerQuoteResponse;
}

Output (sorry for the blurry output, if you click on it, you will see clear result):

Answer 1

1. don't
2. don't

Basically, there is no good or workable way to call an async method from a sync method and wait for the answer. There's "sync over async", but that's an anti-pattern and should be aggressively avoided.

So either:

1. rewrite the caller to be async
2. implement a synchronous version of the API