vb.net 向asp post值,值中包含html代码时报错

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            Dim URL As String = geturl

            Dim myUri As Uri = New Uri(geturl)

            Dim myWebRequest As System.Net.WebRequest = System.Net.WebRequest.Create(URL)

            myHttpWebRequest = CType(myWebRequest, System.Net.HttpWebRequest)

            myHttpWebRequest.KeepAlive = True

            myHttpWebRequest.Timeout = 3000000

            myHttpWebRequest.Method = "POST"

            Dim postdata As String = URLEncoding(text)

            'Dim postdata As String = text



            Dim encoding As System.Text.Encoding

            encoding = System.Text.Encoding.GetEncoding("GB2312")





            Dim byte1 As Byte() = encoding.GetBytes(postdata)

            myHttpWebRequest.ContentType = "application/x-www-form-urlencoded"

            myHttpWebRequest.ContentLength = postdata.Length

            Dim newStream As System.IO.Stream = myHttpWebRequest.GetRequestStream()

            newStream.Write(byte1, 0, byte1.Length)

            newStream.Close()

            Dim myWebResponse As System.Net.WebResponse = myHttpWebRequest.GetResponse()

            myHttpWebResponse = CType(myWebResponse, System.Net.HttpWebResponse)

            Dim iStatCode As Integer = CInt(myHttpWebResponse.StatusCode)

            myHttpWebResponse = CType(myWebResponse, System.Net.HttpWebResponse)

            Dim myStream As System.IO.Stream = myHttpWebResponse.GetResponseStream()

            Dim srReader As System.IO.StreamReader = New System.IO.StreamReader(myStream, System.Text.Encoding.Default)

            Dim sTemp As String = srReader.ReadToEnd()

            http_post = sTemp