vb.net中的404错误，但是在fiddler和邮递员

Question

我正在尝试在现有网站上使用SugarCRM v10但是HttpWebRequest.GetResponse不合作。当我去fiddler4和Postman时，url和请求者在代码中是相同的，我得到200响应。到目前为止这是我的代码（这是函数中的代码）：

Dim request As HttpWebRequest = Nothing
        Dim Reqeuststring As String = myurl
        request = Net.HttpWebRequest.Create(Reqeuststring)
        request.Method = mymethod
        request.ContentType = "application/json"

        Dim byteArray As Byte() = Encoding.UTF8.GetBytes(pstring)
        request.ContentLength = byteArray.Length

        ' Get the request stream.
        Dim dataStream As Stream = request.GetRequestStream()

        ' Write the data to the request stream.
        dataStream.Write(byteArray, 0, byteArray.Length)

        ' Close the Stream object.
        dataStream.Close()
 response = request.GetResponse()

我按照API文档传递url（http://{siteurl}/rest/v10/oath2/token），pString是json格式，在这种情况下，mymethod作为POST传递。