Convert Deserialization method to Async

Question

I am trying to convert this method that deserializes an object into a string with Async/Await.

    public static T DeserializeObject<T>(string xml)
    {
        using (StringReader reader = new StringReader(xml))
        {
            using (XmlReader xmlReader = XmlReader.Create(reader))
            {
                DataContractSerializer serializer = new DataContractSerializer(typeof(T));
                T theObject = (T)serializer.ReadObject(xmlReader);
                return theObject;
            }
        }
    }

Do you mean Async/Await, or just any sort of asynchronous pattern? — Jeff B
– Jeff B, Commented Aug 9, 2012 at 12:58

Marc Gravell · Accepted Answer · 2018-07-28 12:08:05Z

17

Most serialization APIs do not have async implementations, which means the only thing you can really do is wrap a sync method. For example:

public static Task<T> DeserializeObjectAsync<T>(string xml)
{
    using (StringReader reader = new StringReader(xml))
    {
        using (XmlReader xmlReader = XmlReader.Create(reader))
        {
            DataContractSerializer serializer =
                new DataContractSerializer(typeof(T));
            T theObject = (T)serializer.ReadObject(xmlReader);
            return Task.FromResult(theObject);
        }
    }
}

This isn't actually async - it just meets the required API. If you have the option, using ValueTask<T> is preferable in scenarios where the result may often be synchronous/

Either way, you should then be able to do something like:

var obj = await DeserializeObject<YourType>(someXml);
Debug.WriteLine(obj.Name); // etc

without needing to know whether the actual implementation was synchronous or asynchronous.

edited Jul 28, 2018 at 12:08

answered Aug 9, 2012 at 13:41

Marc Gravell

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2 Comments

shtse8 Over a year ago

Noted that the method is still sync because there is no "await" syntax for switching context. It's just a sync Task and meaningless for await it.

Marc Gravell Over a year ago

@shtse8 yes, that's a fair comment - I've clarified

Tamir · Accepted Answer · 2012-08-09 13:13:03Z

2

A little sample, pretty primitive way:

    public delegate T Async<T>(string xml);

    public void Start<T>()
    {
        string xml = "<Person/>";
        Async<T> asyncDeserialization = DeserializeObject<T>;
        asyncDeserialization.BeginInvoke(xml, Callback<T>, asyncDeserialization);
    }

    private void Callback<T>(IAsyncResult ar)
    {
        Async<T> dlg = (Async<T>)ar.AsyncState;
        T item = dlg.EndInvoke(ar);
    }

    public T DeserializeObject<T>(string xml)
    {
        using (StringReader reader = new StringReader(xml))
        {
            using (XmlReader xmlReader = XmlReader.Create(reader))
            {
                DataContractSerializer serializer = new DataContractSerializer(typeof(T));
                T theObject = (T)serializer.ReadObject(xmlReader);
                return theObject;
            }
        }
    }

you define a delegate and using it to Begin/End invoke using callbacks.

using the next versions of C# you can use the async keyword to get your code run asynchronously.

answered Aug 9, 2012 at 13:13

Tamir

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1 Comment

Terrence Over a year ago

Tamir, I am using the next version of C# in Windows8. Could you give me an example using await and async? That is what I am looking for. Thank you.

Peter · Accepted Answer · 2018-04-04 21:22:38Z

0

As you are working with a string as data source doing things async would only introduce more overhead and give you nothing for it.

But if you where reading from a stream you could copy from the source stream to a MemoryStream(buffering all data), then deserialize from the MemoryStream, that would increase the memory usage but would lower the amount of time you will block the thread.

edited Apr 4, 2018 at 21:22

answered Apr 4, 2018 at 20:33

Peter

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Comments

Horosho · Accepted Answer · 2017-08-30 12:16:10Z

-5

You can return

Task.FromResult(theObject)

answered Aug 30, 2017 at 12:16

Horosho

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1 Comment

Dan Watkins Over a year ago

This will run synchronously.

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