รบกวนพี่ๆ ช่วย ดู error ให้หน่อยค่ะ The variable name has already been declared. Variable names must be unique within a query batch or stored procedure

 if (conn.State != ConnectionState.Open)
                {
                    conn.Open();
                }

                cmd.Connection = conn;
                cmd.CommandText = "INSERT INTO tblRepair (RpID, BdID, RmID, DvID, RpDetail, RpRequest)";
                cmd.CommandText += "VALUES ('Rp-' + REPLICATE('0', 5 - LEN(IDENT_CURRENT('tblRepair'))) + CONVERT(nvarchar(50), IDENT_CURRENT('tblRepair')) ,@BdID, @RmID, @DvID, @RpDetail, @RpRequest)";

                cmd.Parameters.Add("@BdID", SqlDbType.NVarChar).Value = ddlBuilding.SelectedValue.ToString();
                cmd.Parameters.Add("@RmID", SqlDbType.NVarChar).Value = ddlRoom.SelectedValue.ToString();
                cmd.Parameters.Add("@RpDetail", SqlDbType.NVarChar).Value = txtRpDetail.Text.Trim();
                cmd.Parameters.Add("@RpRequest", SqlDbType.DateTime).Value = DateTime.Now;
                //cmd.Parameters.Add("@UsID", SqlDbType.NVarChar).Value = ddlUser.SelectedValue.ToString();

                int i;

                for (i = 0; i <= this.CheckBoxList.Items.Count - 1; i++)
                {
                    if (CheckBoxList.Items[i].Selected == true)
                    {
                        cmd.Parameters.Add("@DvID", SqlDbType.NVarChar).Value = CheckBoxList.Items[i].Value;
                    }

                    else if (CheckBox.Checked == true)
                    {
                            cmd.Parameters.Add("@DvID", SqlDbType.NVarChar).Value = txtother.Text.Trim();
                    }
                }