HttpWebRequest to HttpClient post Request

Question

with HttpWebRequest i use this code to post request and wait to get an async response

Private Async Sub SendHttpWebReq(ByVal jsonString as String)
    ' create the HttpWebRequest
    Dim httpWebReq = CType(Net.WebRequest.Create("http://www.foo.foo"), Net.HttpWebRequest)
    ' set the HttpWebRequest
    httpWebReq.Method = "POST"
    httpWebReq.KeepAlive = True
    httpWebReq.ContentType = "application/json"
    With httpWebReq.Headers
       .Add(Net.HttpRequestHeader.AcceptCharSet, "ISO-8859-1,utf-8")
       .Add("X-User", user)
    End With
    ' transform the json String in array of Byte
    Dim byteArray as Byte() = Encoding.UTF8.GetBytes(jsonString)
    ' set the HttpWebRequest Content length
    httWebReq.ContentLEngth = byteArray.Length
    ' create a HttpWebRequest stream
    Dim dataStream as IO.Stream = httpWebReq.GetRequestStream()
    ' send the request in a stream
    dataStream.Write(byteArray, 0, byteArray.Length)
    dataStream.Close()
    ' create the HttpWebRequest response
    Dim Response as Net.WebResponse = Await httpWebReq.GetResponseAsync()
    Dim ResponseStream as IO.Stream = Response.GetResponseStream()

End Sub

I tried to 'translate' the code to HttpClient in this mode

Dim HttpClientReq as HttpClient
With HttpClientReq
    .BaseAddress = New Uri("Http://www.foo.foo")
    .DefaultRequestHeaders.Accept.Clear()
    .DefaultRequestHeaders.Accept.Add(New Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json")
    .DefaultRequestHeaders.Add("X-User", user)
End With

Private Async Sub SendHttpClientReq(Byval jsonString as String)
    Dim Request As Net.Http.HttpRequestMessage
    Request.Content = New Net.Http.StringContent(jsonString, System.Text.Encoding.UTF8, "application/json")
    Dim Response as Net.Http.HttpResponseMessage = Await HttpClientReq.PostAsync(HttpClientReq.BaseAddress)

End sub

But i need to understand how to approach to HttpClient.

While in the HttpWebRequest: i

• create an instance of the class
• set the parameters (and headers)
• post a request
• create a response that wait for the server response
• hooking the response to the request, i receive the server response

With HttpClient: i

• create the instance of the class
• set the parameters (and headers)
• post a request
• i don't see any method that let me hook a response to a request, so i don't know how to wait to receive the response.

Any suggestion?

Also in c#

Answer 1

Net.Http.HttpClient has a primarily task based API. As for hooking a response to a request, No need. Just await the resposne and use it as desired once returned.

Dim client As HttpClient
With client
    .BaseAddress = New Uri("Http://www.foo.foo")
    .DefaultRequestHeaders.Accept.Clear()
    .DefaultRequestHeaders.Accept.Add(New Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json")
    .DefaultRequestHeaders.Add("X-User", user)
End With

'...'

Private Async Function PostAsync(Byval jsonString as String) As Task

    Dim content As New Net.Http.StringContent(jsonString, System.Text.Encoding.UTF8, "application/json")
    Dim response As Net.Http.HttpResponseMessage = Await client.PostAsync("", content)

    Dim result As String = Await response.Content.ReadAsStringAsync()

    'do something with the result.'

End Function

Avoid async Subs/void. In this case a function returning a Task would be required to properly await the async functions.