I found that the stream is at the end, i will have to set it to the beginning
Dim InStream As Stream
Dim Len As Integer
InStream = HttpContext.Current.Request.InputStream
InStream = CType(InStream, Stream)
Len = CInt(InStream.Length)
Dim ByteArray(Len) As Byte
InStream.Seek(0, SeekOrigin.Begin);
InStream.Read(ByteArray, 0, Len)
Dim jsonParam As String
jsonParam = System.Text.Encoding.UTF8.GetString(ByteArray)