主题：按照图片所示我的请求是不是缺少什么?

Dim result As String

Try

    Dim web As New System.Net.WebClient()

    web.Proxy = Nothing

    web.Headers.Add("Content-Type", "application/json")

    Dim body As New Newtonsoft.Json.Linq.JObject

    body("username") = "xxx"

    body("password") = "xxx"

    result = web.UploadString("xxx", body.ToString())

Catch ex As System.Net.WebException

    Dim stream As System.IO.Stream = ex.Response.GetResponseStream()

    Dim reader As New System.IO.StreamReader(stream)

    result = reader.ReadToEnd()

End Try