c# return data from Asynchronous function

Question

I have two methods

public void GetEmp()
{
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new System.Uri("http://sdw2629/empservice/EmployeeInfo.svc/Employee"));
    request.Method = "GET";
    request.ContentType = "application/json; charset=utf-8";

    request.BeginGetResponse(new AsyncCallback(ReadWebRequestCallback), request);  

}

and

private void ReadWebRequestCallback(IAsyncResult callbackResult)
{
    HttpWebRequest myRequest = (HttpWebRequest)callbackResult.AsyncState;
    using (HttpWebResponse myResponse = (HttpWebResponse)myRequest.EndGetResponse(callbackResult))
    {
        using (StreamReader httpwebStreamReader = new StreamReader(myResponse.GetResponseStream()))
        {
            string results = httpwebStreamReader.ReadToEnd();
            //execute UI stuff on UI thread.              
        }
    }
}

Here i want to return a string "results" to some other method like this

string data= obj1.GetEmp()

How can i achieve this.. Any help would be appriciated.. Thanks

Why dont you use GetResponse() if you want a synchronous [blocking ] call? — alexm
– alexm, Commented Apr 19, 2016 at 6:20

Andrii Tretiak · Accepted Answer · 2016-04-19 07:10:10Z

5

Easiest way to do this is rewrite method using async, like this:

public async Task<string> GetEmpAsync()
{
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new System.Uri("http://sdw2629/empservice/EmployeeInfo.svc/Employee"));
    request.Method = "GET";
    request.ContentType = "application/json; charset=utf-8";
    var response = await request.GetResponseAsync();
    using (StreamReader httpwebStreamReader = new StreamReader(response.GetResponseStream()))
    {
        string results = await httpwebStreamReader.ReadToEndAsync();
        //execute UI stuff on UI thread.
        return results;
    }

}

Then you can get result with code like this:

var results = await GetEmpAsync();

If you are using older version and don't have async, you can do it in blocking way to get result:

public string GetEmpBlocking()
{
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new System.Uri("http://sdw2629/empservice/EmployeeInfo.svc/Employee"));
    request.Method = "GET";
    request.ContentType = "application/json; charset=utf-8";
    var response = request.GetResponse();
    using (StreamReader httpwebStreamReader = new StreamReader(response.GetResponseStream()))
    {
        string results = httpwebStreamReader.ReadToEnd();
        //execute UI stuff on UI thread.
        return results;
    }
}

And get result like this:

var results = GetResultBlocking();

Р.S. you can also consider using Microsoft.Bcl.Async to support async in earlier versions.

edited Apr 19, 2016 at 7:10

answered Apr 19, 2016 at 6:20

Andrii Tretiak

3,2712 gold badges22 silver badges33 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Sagar Jagadesh Over a year ago

at this line var results = await GetempAsync(); i am getting this error "MyClass' does not contain a definition for 'GetempAsync' and no extension method 'GetempAsync' accepting a first argument of type 'MyClass' could be found (are you missing a using directive or an assembly reference?)"

Andrii Tretiak Over a year ago

@SagarJagadesh sorry there was a typo, there should be var results = await GetEmpAsync();. Basicaly it's just call of your method with await keyword before it.

Sagar Jagadesh Over a year ago

Hi i am getting error as "Unknown identifier: request " at this line "await request.GetResponseAsync(); " can u please suggest ?

Andrii Tretiak Over a year ago

@SagarJagadesh what version of .Net are you using? If it's 4.5 or upper please check that you added 'async' to method definition. If it's less than 4.5 you need add Microsoft.Bcl.Async lib to support async.

Sagar Jagadesh Over a year ago

i just replaced this line " var response = await request.GetResponseAsync();" with new line "var response = (HttpWebResponse) await request.GetResponseAsync().ConfigureAwait(false);".. Its working fine..Thanks for the help..

dennis · Accepted Answer · 2016-04-19 06:25:53Z

2

Just use the

var resp = request.GetResponse();

instead of the

request.BeginGetResponse(...);

With the synchrounous GetResonse, you can return the string directly.

public string GetEmp()
{
    var request = (HttpWebRequest)HttpWebRequest.Create(new System.Uri(@"http://.../data.json"));
    request.Method = "GET";
    request.ContentType = "application/json; charset=utf-8";

    var resp = request.GetResponse();

    using (var httpWebStreamReader = new StreamReader(resp.GetResponseStream()))
    {
        var result = httpWebStreamReader.ReadToEnd();
        return result;
    }
}

answered Apr 19, 2016 at 6:25

dennis

3263 silver badges10 bronze badges

Collectives™ on Stack Overflow

c# return data from Asynchronous function

2 Answers 2

5 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related