主题：调用其他api接口的时候遇到 ContentLength ,看了一下教程HttpClient没有地方可以设置这个参数

Dim request As System.Net.HttpWebRequest = CType(System.Net.WebRequest.Create(ExchangeURL ), System.Net.HttpWebRequest)
request.Method = "POST"

Dim postData As String = "grant_type=refresh_token&refresh_token=" & _XeroInfo.refresh_token
Dim byteArray As Byte() = Encoding.UTF8.GetBytes(postData)

request.C
request.ContentLength = byteArray.Length

request.Headers.Add("Authorization", "Basic " & base64EncodedText)

Dim dataStream As System.IO.Stream = request.GetRequestStream()
dataStream.Write(byteArray, 0, byteArray.Length)
dataStream.Close()

Dim response As System.Net.HttpWebResponse = CType(request.GetResponse(), System.Net.HttpWebResponse)
Dim responseStream As System.IO.Stream = response.GetResponseStream()
Dim reader As New System.IO.StreamReader(responseStream, Encoding.UTF8)

Dim responseContent As String  = reader.ReadToEnd()

responseStream.Close()
response.Close()