c# HttpClient PostAsync 与异步和等待不起作用

Question

我在尝试使用 HttpClient PostAsync 并使用 async 和 await 从 WebApi 1 发布到 WebApi 2 时遇到了死锁情况。

下面是WebAPI 1：

public HttpResponseMessage Get([FromUri]int oid) 
{
    var orderdetails = _orderServices.GetOrderDetails(oid);

    var xml = new XmlMediaTypeFormatter();
    xml.UseXmlSerializer = true;
    string orderdetailsser = Serialize(xml, orderdetails);

    var result = PostXml(orderdetailsser);

    return Request.CreateResponse(HttpStatusCode.OK);
}

public static async Task<HttpResponseMessage> PostXml(string str)
{
    using (var client = new HttpClient())
    {

        client.BaseAddress = new Uri("http://localhost:58285/");

        var content = new StringContent(str);
        var response = await client.PostAsync("api/default/ReceiveXml", content).ConfigureAwait(false);
        return response;
    }

}

和WebApi2：

[System.Web.Http.HttpPost]
public HttpResponseMessage ReceiveXml(HttpRequestMessage request)
{

    var xmlDoc = new XmlDocument();
    xmlDoc.Load(request.Content.ReadAsStreamAsync().Result);

    xmlDoc.Save(@"C:\xmlfiles\xml2.xml");

    XmlSerializer deserializer = new XmlSerializer(typeof(OrderInfoModel));
    TextReader reader = new StreamReader(@"C:\xmlfiles\xml2.xml");
    object obj = deserializer.Deserialize(reader);
    OrderInfoModel orderdetails = (OrderInfoModel)obj;
    reader.Close();

    var patient_id = _patientServices.ProcessPatient(orderdetails.Patient, orderdetails.OrderInfo);
    var orderid = _orderServices.ProcessOrder(orderdetails.Patient, orderdetails.OrderInfo, patient_id);

    if (orderdetails.OrderNotes != null && orderdetails.OrderNotes.Count() > 0)
    {
        var success = _orderServices.ProcessOrderNotes(orderid, orderdetails.OrderNotes);
    }

    var prvid = _orderServices.ProcessOrderProvider(orderid, orderdetails.ReferringProvider);

    var shpngid = _orderServices.ProcessOrderShipping(orderid, orderdetails.ShippingInfo);

    var payerid = _orderServices.ProcessOrderPayer(orderid, orderdetails.Insurances);

    return Request.CreateResponse(HttpStatusCode.OK, orderid);
}

我没有从 WebAPI 2 收到任何回复 WebAPI 1。我已经浏览了几篇关于死锁情况的在线文章。但是，在我的情况下，我无法解决僵局。我在这里做错了什么？我是否正确使用了async 和await？

Answer 1

要构建我上面的评论，请修改您的代码，以便您不会阻塞 async 操作。此外，_orderServices.GetOrderDetails(oid); 听起来像是一种访问数据库的方法，因此应该是 await _orderServices.GetOrderDetailsAsync(oid);，其中您使用可用于数据库访问的任何 async api。

[HttpGet()]
public async Task<HttpResponseMessage> Get([FromUri]int oid) {
    var orderdetails = _orderServices.GetOrderDetails(oid);

    var xml = new XmlMediaTypeFormatter();
    xml.UseXmlSerializer = true;
    string orderdetailsser = Serialize(xml, orderdetails);

    var result = await PostXml(orderdetailsser);

    return Request.CreateResponse(HttpStatusCode.OK);
}

public static async Task<HttpResponseMessage> PostXml(string str) {
    using(var client = new HttpClient()) {

        client.BaseAddress = new Uri("http://localhost:58285/");

        var content = new StringContent(str);
        var response = await client.PostAsync("api/default/ReceiveXml", content).ConfigureAwait(false);
        return response;
    }

}

[HttpPost()]
public async Task<HttpResponseMessage> ReceiveXml(HttpRequestMessage request) {

    var xmlDoc = new XmlDocument();
    xmlDoc.Load(await request.Content.ReadAsStreamAsync());

    xmlDoc.Save(@"C:\xmlfiles\xml2.xml");

    XmlSerializer deserializer = new XmlSerializer(typeof(OrderInfoModel));
    TextReader reader = new StreamReader(@"C:\xmlfiles\xml2.xml");
    object obj = deserializer.Deserialize(reader);
    OrderInfoModel orderdetails = (OrderInfoModel)obj;
    reader.Close();

    var patient_id = _patientServices.ProcessPatient(orderdetails.Patient, orderdetails.OrderInfo);
    var orderid = _orderServices.ProcessOrder(orderdetails.Patient, orderdetails.OrderInfo, patient_id);

    if(orderdetails.OrderNotes != null && orderdetails.OrderNotes.Count() > 0) {
        var success = _orderServices.ProcessOrderNotes(orderid, orderdetails.OrderNotes);
    }

    var prvid = _orderServices.ProcessOrderProvider(orderid, orderdetails.ReferringProvider);

    var shpngid = _orderServices.ProcessOrderShipping(orderid, orderdetails.ShippingInfo);

    var payerid = _orderServices.ProcessOrderPayer(orderid, orderdetails.Insurances);

    return Request.CreateResponse(HttpStatusCode.OK, orderid);
}

资源

Don't Block on Async Code

Avoid Async Void