VB获取Json文件错误：“远程服务器返回错误：（400）错误的请求。”

Question

Code works on other web pages but i get an error with this particular web page. any help is appreciated.

    Private Function GetJson()

    Dim JsonString As String

    Dim request As Net.WebRequest = Net.WebRequest.Create("https://api-public.sandbox.gdax.com/products") 'set url
    request.Method = "GET"

    Dim response As Net.WebResponse = request.GetResponse()
    Dim inputstream1 As IO.Stream = response.GetResponseStream()   ' define the stream
    Dim reader As New IO.StreamReader(inputstream1)                ' get the data stream set

    JsonString = reader.ReadToEnd                                   'saves stream in jsonstring

    ProgressTxtBx.Text = JsonString

    'Dim read = Newtonsoft.Json.Linq.JObject.Parse(JsonString)       'Parsed

    inputstream1.Dispose()                                      ' CLEAN UP
    reader.Close()                                              ' 
    response.Close()                                            '

End Function

Answer 1

The absence of User-Agent header generated Bad request . In order to apply it, you need to cast WebRequest to HttpWebRequest .

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim JsonString$
    Dim req = DirectCast(Net.WebRequest.Create("https://api-public.sandbox.gdax.com/products"), HttpWebRequest)
    req.Method = "GET"
    req.UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.15 Safari/537.36 OPR/51.0.2830.0 (Edition developer)"
    Using resp = req.GetResponse()
        Using strm = resp.GetResponseStream()
            Using sr = New StreamReader(strm)
                JsonString = sr.ReadToEnd()
            End Using
        End Using
    End Using
    Dim json = Newtonsoft.Json.Linq.JObject.Parse(JsonString)
End Sub

Answer 2

I believe you could trap for WebExceptions to get at any additional error information returned by the server.

Dim response As Net.WebResponse
Try 
    response = request.GetResponse()
Catch ex As WebException 
    If ex.Response IsNot Nothing...
        response = ex.Response
    End If
End Try