从Dynamics CRM插件调用异步库

Question

我有一个异步库，可连接到第三方系统API。我正在尝试在Dynamics C＃插件中使用此库在第三方系统中创建新记录。只要插件一次只在一个实体上运行，我编写的代码就可以正常工作。但是，如果我同时在两个不同实体上启动该插件，则会收到错误消息：

  

无法更新星标。错误-对象引用未设置为对象的实例。 ：System.NullReferenceException：：位于COHEN.APIConnector.Connectors.StarConnector.d__2`1.MoveNext（）

我不太确定是什么导致了此错误或如何解决该错误。似乎与我编写的用于连接到API的库的异步特性有关。是什么会导致此错误，有哪些解决方案？

插件代码

APIResponse<COHEN.APIConnector.Model.Entity.ContractJob> response = new APIResponse<COHEN.APIConnector.Model.Entity.ContractJob>();

Task.WaitAll(Task.Run(async () => response = await starConnector.Create(starJob))); 

库代码

public async Task<APIResponse<T>> Create<T>(T entity) where T : EntityBase
{
    APIResponse<T> response = new APIResponse<T>();

    try
    {
        using (HttpClient client = new HttpClient())
        {
            client.BaseAddress = new Uri(Helpers.GetSystemUrl(Application.Star));
            client.DefaultRequestHeaders.Clear();
            client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/xml"));

            response.RequestURL = "Calling ToJSON";

            string json = await entity.ToJSON(Application.Star);

            response.RequestURL = "JSON: " + json;

            response.RequestURL = "RunTask?taskid=" + (int)TaskID.CREATE + "&entity=" +
                await MapSingleton.Instance.GetFieldName(Application.Star, entity.Type, FieldType.EntityName) +
                "&json=" + json;

            using (HttpResponseMessage responseMessage = await client.GetAsync(
                "RunTask?taskid=" + (int)TaskID.CREATE + "&entity=" +
                await MapSingleton.Instance.GetFieldName(Application.Star, entity.Type, FieldType.EntityName) +
                "&json=" + json
            ))
            {
                // Check TaskCentre response
                if (responseMessage.StatusCode == HttpStatusCode.OK)
                {
                    XmlDocument xmlDocument = new XmlDocument();
                    xmlDocument.LoadXml(await responseMessage.Content.ReadAsStringAsync());

                    // Check API Response
                    string responseStatusCode = xmlDocument.GetElementsByTagName("StatusCode").Item(0).InnerText;
                    if (responseStatusCode != "")
                    {
                        StatusCode statusCode = (StatusCode)Convert.ToInt32(responseStatusCode);
                        string statusMessage = xmlDocument.GetElementsByTagName("StatusMessage").Item(0).InnerText;

                        if (statusCode == StatusCode.Created)
                        {
                            XmlDocument xmlData = new XmlDocument();
                            xmlData.LoadXml("<data>" + xmlDocument.InnerText.Substring(0, xmlDocument.InnerText.Length - (xmlDocument.InnerText.Length - xmlDocument.InnerText.LastIndexOf("row") - 4)) + "</data>");
                            JObject data = JObject.Parse(JsonConvert.SerializeXmlNode(xmlData));

                            await response.SetValues(Application.Star, entity.Type, data["data"]["row"], entity.ID);
                        }

                        response.StatusCode = statusCode;
                        response.StatusReason = statusMessage;
                    }
                    else
                    {
                        response.StatusCode = StatusCode.Error;
                        response.StatusReason = "No Status Code Returned - " + response.StatusReason;
                    }
                }
                else
                {
                    response.StatusCode = (StatusCode)responseMessage.StatusCode;
                    response.StatusReason = responseMessage.ReasonPhrase;
                }
            }
        }
    }
    catch (Exception e)
    {
        response.StatusCode = StatusCode.Error;
        response.StatusReason = e.Message + " : " + e.GetType().ToString() + " : " + e.InnerException + " : " + e.StackTrace;
    }

    return response;
}

Answer 1

根据Dynamics Developer Guide，您不应在插件中使用全局变量。我使用全局变量访问导致此问题的第三方库。下面的链接文档的相关部分

  

为提高性能，Dynamics 365 for Customer Engagement缓存插件实例。应当将插件的Execute（IServiceProvider）方法编写为无状态的，因为并非每次调用该插件时都会调用该构造函数。同样，多个系统线程可以同时执行插件。每次调用的所有状态信息都存储在上下文中，因此，除非该数据是从提供给构造函数的配置参数中获取的，否则您不应使用全局变量或尝试将任何数据存储在成员变量中供下次插件调用时使用。插件注册的更改将导致该插件被重新初始化。