DraftParam draft_param = new DraftParam
{
  draft_msg = new Message
  {
    message_conv_id = "1234",
    message_conv_type = TIMConvType.kTIMConv_Group,
    message_elem_array = new List<Elem>{new Elem
    {
      elem_type = TIMElemType.kTIMElem_Text,
      text_elem_content = Input.text
    }},
  }
}
TIMResult res = TencentIMSDK.ConvSetDraft(conv_id, conv_type, draft_param);