use async /await with synchronous methods

Question

How to make such piece of code run asynchronously with synchronous System.Xml.Serialization.XmlSerializer.Deserialize method which forces me to use Result all the way long?

    ...
    await GetContent(url) 
    ...

    private async Task<Node> GetContent (string url)
   {
        var response = _httpClient.GetAsync(url).Result;
        var ser = new XmlSerializer(typeof(Node));
        retVal = (Node)ser.Deserialize(response.Content.ReadAsStreamAsync().Result);
    }

We need more information here, is the containing method `async`? — maccettura, Feb 24 '20 at 16:41
THe problem is the parent method, not `Deserialize`. Make it `async Task` at least and use `await` to read the values. *DON'T* put the calls in the same line. Even for synchronous code it makes debugging a mess. — Panagiotis Kanavos, Feb 24 '20 at 16:42
You should use `using var stream= await response.Content.ReadAsStreamAsync(); retVal=(Node)ser.Deserialize(content);` — Panagiotis Kanavos, Feb 24 '20 at 16:43
Does this answer your question? [How to use HttpClient without async](https://stackoverflow.com/questions/40208647/how-to-use-httpclient-without-async) — Posix, Feb 24 '20 at 16:43
@DavidKosorin the real answer there is "don't try to make this synchronous" — Panagiotis Kanavos, Feb 24 '20 at 16:44
BTW that stream *has* to be disposed, otherwise the connection to the server remains open. The current code is leaking connections — Panagiotis Kanavos, Feb 24 '20 at 16:45

score 3 · Accepted Answer · edited Feb 24 '20 at 17:50

3

The method is already async so there's no reason to use .Result. Just use await and remember to close the stream, otherwise the server connection remains open:

private async Task<Node> GetContent (string url)
{
    var response = await _httpClient.GetAsync(url);

    //**IMPORTANT** Ensure the stream is closed
    using(var stream= await response.Content.ReadAsStreamAsync())
    {
       var ser = new XmlSerializer(typeof(Node));
       var retVal = (Node)ser.Deserialize(stream);
       return retVal;
    }
}

edited Feb 24 '20 at 17:50

mk_yo

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answered Feb 24 '20 at 16:47

Panagiotis Kanavos

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there's Result after http call. How deal with it? – mk_yo Feb 24 '20 at 16:49
this Result might be left by mistake – mk_yo Feb 24 '20 at 16:55

use async /await with synchronous methods

1 Answers1