Question

我刚开始使用DocumentDB，所以我已经下载了.NET SDK。在从Azure网站下载的使用示例之后，我尝试创建一些文档以保存到DocumentDB。示例代码如下

   public static void Main(string[] args)
    {
        try
        {
            GetStartedDemo().Wait();
        }
        catch (DocumentClientException de)
        {
            // omissis
        }
    }
    private static async Task GetStartedDemo()
    {
        var client = new DocumentClient(new Uri(EndpointUrl), AuthorizationKey);

        Family andersonFamily = new Family
        {
            Id = "AndersenFamily",
            LastName = "Andersen",
            Parents = new Parent[] {
                new Parent { FirstName = "Thomas" },
                new Parent { FirstName = "Mary Kay"}
                },
            Children = new Child[] {
                    new Child
                    {
                        FirstName = "Henriette Thaulow",
                        Gender = "female",
                        Grade = 5,
                        Pets = new Pet[] {
                            new Pet { GivenName = "Fluffy" }
                        }
                    }
                },
            Address = new Address { State = "WA", County = "King", City = "Seattle" },
            IsRegistered = true
        };

        await client.CreateDocumentAsync("dbs/" + database.Id + "/colls/" + documentCollection.Id, andersonFamily);

        client.Dispose();
    }

此代码效果很好。我的代码几乎相同，除了我将JSON保存到DB中的类。它总是停在线上

await client.CreateDocumentAsync("dbs/" + database.Id + "/colls/" + coll.Id, this);

我的整个代码如下

public static async Task Save(int UserId, int productID, string code, string language, string dataOraLettura, string longitudine, string latitudine, string nazione_lettura)
    {
        CultureInfo ciEN = CultureInfo.GetCultureInfo("en-US");
        CodeType ScannedCode = new CodeType
        {
            Code = code,
            ProductId = productID,
            ScanLog = new List<CodeType.ScanDataType>()
        };
        ScannedCode.ScanLog.Add(new CodeType.ScanDataType
        {
            Location = new Microsoft.Azure.Documents.Spatial.Point(double.Parse(longitudine, ciEN.NumberFormat), double.Parse(latitudine, ciEN.NumberFormat)),
            ScanType = CodeType.ScanDataType.eScanType.Alert,
            UserId = UserId.ToString(),
            TimeStamp = long.Parse(DateTime.Now.ToString("yyyyMMddHHmmssffff"))
        });
        await ScannedCode.AddAsync();

    }

   public async Task AddAsync()
    {
        using (DocumentClient client = new DocumentClient(new Uri(WebConfigurationManager.AppSettings["DbURI"]), WebConfigurationManager.AppSettings["DbKEY"]))
        {
            var CodeDocuments = client.CreateDocumentQuery<CodeType>("dbs/" + database.Id + "/colls/" + coll.Id).Where(a => a.Code == this.Code).ToArray();
            if (CodeDocuments.Length == 0)
                await client.CreateDocumentAsync("dbs/" + database.Id + "/colls/" + coll.Id, this);
        }
    }

似乎异步任务阻塞并且它不会将控制权返回给调用者，然后保持循环执行。

Answer 1

正确，你有一个经典的异步阻止另一个异步的情况。您应该在等待ScannedCode.AddAsync（）时将ConfigureAwait设置为false;

public Node removeKthFromLast(Node head, int k) {
    int n;
    Node p = head;
    for (n=0;head != null;n++) {
      p = head.next;
    }
    return removeKthFromLastAux(head, n-k);
}

private Node removeKthFromLastAux(Node head, int ik) {
    if (head == null) {
        return null;
    }
    if (ik == 0) {
        return head.next;
    }
    head.next = removeKthFromLastAux(head, ik-1);
    return head;
}

这使得它在线程池线程而不是ASP.NET请求上下文中恢复。

您可以阅读以下文章http://blog.stephencleary.com/2012/07/dont-block-on-async-code.html，该文章解释了这一点以及使用异步代码时的其他最佳做法。

在C＃中以异步方式创建新的DocumentDB文档的问题

1 个答案: