是否有可能有一个可编辑的DetailsView实体与子类的对象？ [英] Is it possible to have an editable DetailsView for entity objects with subclasses?

问题描述

假如我有两个类，一个从 EntityObject 衍生另从第一来源：

Suppose I have two classes, one derived from EntityObject and the other derived from the first:

public class Gizmo : EntityObject { ... }
public class SpecialGizmo : Gizmo { ... }

在ASP.NET页面中，用户选择列表中的一个小物件（一个 GridView控件）和小物件的细节则$ P $在psented DetailsView控件。我们的目标是用户能够查看的和编辑的细节。

In the ASP.NET page, the user selects a Gizmo in a list (a GridView) and that Gizmo’s details are then presented in a DetailsView. The goal is for the user to be able to view and edit the details.

下面是相关的 DetailsView控件及其相关联的 EntityDataSource ：

Here is the relevant DetailsView and its associated EntityDataSource:

<asp:DetailsView ID="GizmosDetailsView" DataSourceID="dsGizmoDetails"
    AutoGenerateEditButton="True" AutoGenerateInsertButton="True"
    AutoGenerateRows="False" DataKeyNames="GizmoId" runat="server">
    <Fields>
        <asp:BoundField DataField="GizmoId" HeaderText="GizmoId" ReadOnly="True" SortExpression="GizmoId" />
        <asp:BoundField DataField="Description" HeaderText="Description" SortExpression="Description" />
        <!-- ... etc. --->
    </Fields>
</asp:DetailsView>

<asp:EntityDataSource ID="dsGizmoDetails" runat="server" ConnectionString="[...]"
    DefaultContainerName="[...]" EnableFlattening="False" EnableUpdate="True"
    Where="it.[GizmoId] = @GizmoId">
    <WhereParameters>
        <asp:ControlParameter ControlID="gvwGizmos" Name="GizmoId" PropertyName="SelectedValue" Type="Int64" />
    </WhereParameters>
</asp:EntityDataSource>

以上失败，出现以下异常：

The above fails with the following exception:

InvalidOperationException异常：无论CommandText中或EntitySetName必须定义

InvalidOperationException: Either CommandText or EntitySetName must be defined.

这是可以理解的。然而，这两个选项presented碰坏：

That’s understandable. However, both options presented break something:

• 如果我想补充 EntitySetName =小玩意儿，那么只有实际类型的实体小玩意儿是永远presented。如果 SpecialGizmo 被选中，DetailsView控件出现空白。

• If I add EntitySetName="Gizmo", then only entities of actual type Gizmo are ever presented. If a SpecialGizmo is selected, the DetailsView comes up blank.

如果我添加一个的CommandText （或选择）的属性，那么 DetailsView控件不再支持更新数据。一个工作的编辑按钮（使编辑UI显示）是存在的，但后来做点击后更新的编辑根本什么都不做。

If I add a CommandText (or a Select) attribute, then the DetailsView no longer supports updating the data. A working "edit" button (that makes edit UI appear) is there, but then clicking "Update" after making edits simply does nothing.

有没有这个两难问题得到妥善解决？

Is there a proper solution to this dilemma?

推荐答案

我解决了这个使用下面的技巧：

I solved this using the following hack:

• 执行指定的CommandText 数据源，这使得 DetailsView控件无法更新数据上自动，但更新UI仍然可用。

• Do specify a CommandText on the data source, which makes the DetailsView unable to update the data automatically, but the update UI is still available.

将 DetailsView控件的 OnItemUpdating 事件是这样的：

protected void GizmoDetailsView_Updating(object sender,
        DetailsViewUpdateEventArgs e)
{
    db.ExecuteStoreCommand(/* use e.Keys["GizmoId"] and e.NewValues */);
    db.SaveChanges();

    // manually set the DetailsView back to read-only mode
    GizmoDetailsView.ChangeMode(DetailsViewMode.ReadOnly);

    // need to cancel the event, as otherwise we get the following exception:
    // InvalidOperationException: Update is disabled for this control.
    e.Cancel = true;
}

此解决方案的缺点： 依靠这是正是如此更新的数据页面上的其他控件，不刷新直到被用户手动重新加载页面。

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