这个是李维的解决办法。就是关于主明细更新的

//保存按钮 procedure TWebForm1.Button1_Click(sender: System.Object; e: System.EventArgs);
var
aJoiner : Joiner;
aSeminar : DevCoSeminar;
begin
aJoiner := CreateJoiner(tbName.Text, tbEMail.Text);
aSeminar := GetSeminarFromName(ddlSeminars.SelectedItem.Text);
aJoiner.joins.Add(aSeminar);
UpdateDatabase;
end; //CreateJoiner 方法 function TWebForm1.CreateJoiner(const sName, sEMail: String): Joiner;
begin
Result := Joiner.Create(EcoSpace);
Result.Name := sName;
Result.EMail := sEMail;
end; //GetSeminarFromName 方法 他不是添加ID。而是用名称查找的办法 function TWebForm1.GetSeminarFromName(const sName: String): DevCoSeminar;
var
anElement : IElement;
begin
Result := nil;
for anElement in ehSeminars.Element.GetAsCollection do
begin
Result := anElement.AsObject as DevCoSeminar;
if (Result.Name = sName) then
break;
end;
end;