Problems for create new DocumentDB documents in async in C#

Question

I'm at the beginning for using DocumentDB so I've downloaded the .NET SDK. Following the using example downloaded from Azure website, I'm trying to create some documents for saving to DocumentDB. The example code is the following

   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();
    }

This code works good. My code is almost the same except for the class I pass for saving in JSON into DB. It always stops on the line

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

My entire code is the following

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);
        }
    }

It seems as the asynchronous task blocks and it doesn't get back the control to the caller then remain in loop execution.

Buncha little things: ScannedCode.AddAsync() doesn't seem static, yet it's called as such. Are you certain you don't have an overload? How many times do you need to repeat the "dbs/.../colls/" pattern before you extract it? If you have 20 parameters on a method you've surely missed one - put them in a class already. Don't follow how the example hides an exception — Sten Petrov
– Sten Petrov, Commented Feb 11, 2016 at 22:41
@StenPetrov This isn't a code-review; the OP asked about an async issue. No need to throw out criticisms about the coding style. — David Makogon
– David Makogon, Commented Feb 12, 2016 at 21:08
ScannedCode.AddAsync() doesn't seem static, that's what I'd check first. The question needs a review itself, there's not sufficient information to go on.... and in some such cases if the OP were to refactor their own code they'd find the error themselves. And your point is good, hence my reply is a comment, not an answer — Sten Petrov
– Sten Petrov, Commented Feb 12, 2016 at 21:51
Try changing await client.CreateDocumentAsync to client.CreateDocumentAsync(...).Result — Arnab Chakraborty
– Arnab Chakraborty, Commented Feb 12, 2016 at 23:19

Ryan CrawCour · Accepted Answer · 2016-03-17 18:23:26Z

3

Correct, you have a classic case of async blocking another async. You should set ConfigureAwait to false on await ScannedCode.AddAsync();

 await ScannedCode.AddAsync().ConfigureAwait(false);

This makes it resume on a thread pool thread instead of the ASP.NET request context.

You can read the following article http://blog.stephencleary.com/2012/07/dont-block-on-async-code.html which explains this very well as well as other best practices while using Async code.

answered Mar 17, 2016 at 18:23

Ryan CrawCour

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