.NET Framework 4 VB.Net Call an API

Question

I am working in an "old" VB.Net application. I wish to make a call to an API, check if I got a 404, parse the JSON result and all the other usual things you can do with an API call.

What is the cleanest way of doing this? I thought I can use the HttpClient class, but I can't apparently! VS 2017 is not giving me the option of adding System.Net.Http as an Import.

CODE

Right now I'm doing this which seems messy.

Public Function GetUserInfo(ByVal authTokenBytes As Byte()) As WebPayWS.GetUserInfoResult
  Dim token As New token
  token.token1 = authTokenBytes
  Dim userInformation As GetUserInfoResult = _myService.GetUserInfo(token)
  If AccountExists(userInformation.accountno) Then
    Dim response As String = GetAccountInfoFromApi(userInformation.accountno)
  End If
  Return userInformation
End Function

Private Function GetAccountInfoFromApi(accountno As String) As String
  Dim accountInformationUrl As String = "URL"
  Dim webClient As WebClient = New WebClient()
  Return webClient.DownloadString(New Uri(accountInformationUrl))
End Function

Am I stuck with WebClient? If yes, how do I check for a 404 using WebClient?

Answer 1

You can wrap it in an exception with the WebClient check this out

Private Function GetAccountInfoFromApi(accountno As String) As String
Dim accountInformationUrl As String = "URL"
Dim webClient As WebClient = New WebClient()
'Return webClient.DownloadString(New Uri(accountInformationUrl))
Dim retString As String

Try 
    retString = webClient.DownloadString(New Uri(accountInformationUrl))

   Catch ex As WebException
    If ex.Status = WebExceptionStatus.ProtocolError AndAlso ex.Response IsNot Nothing Then
        Dim resp = DirectCast(ex.Response, HttpWebResponse)
        If resp.StatusCode = HttpStatusCode.NotFound Then
            ' HTTP 404
            'other steps you want here
        End If
    End If
    'throw any other exception - this should not occur
    Throw
End Try
Return retString

End Function

Answer 2

Add a reference first

• Right click on project
• Add...
  • Reference...
• Browse
• C:\Program Files (x86)\Microsoft ASP.NET\ASP.NET MVC 4\Assemblies\System.Net.Http.dll
• Ok

Now, you can import

Imports System.Net.Http

You can also use NuGet, see https://stackoverflow.com/a/13668810/832052