Question

我正在使用ASP.NET 3.5 SP1，我有一个问题，我一直坚持。我有一个ASPX页面，我有2个转发器控件，1个嵌套在另一个中。从后面的代码我有一个简单的LINQ To Entities查询，它检索数据，然后我将这些数据绑定到转发器控件。 ASPX页面如下所示：

<asp:Repeater ID="rptrMain" runat="server">
    <ItemTemplate>
        <asp:Label ID="lblName" runat="server"  ></asp:Label>
        <asp:Label ID="lblDescription" runat="server"></asp:Label>                 
        <asp:Repeater Runat="server" ID="rptrSub">
            <ItemTemplate>
                <asp:Label ID="lblPartName" runat="server" ></asp:Label>
                <asp:Label ID="lblManufacturerName" runat="server" ></asp:Label>
            </ItemTemplate>
        </asp:Repeater>
     </ItemTemplate>
</asp:Repeater>

我将数据绑定到后面代码中的转发器，如下所示：

var q = from inventories in itemContext.Inventory.Include("Parts.Manufacturer")
        select inventories;

List<Inventory> inventoryList = q.ToList();
rptrMain.DataSource = inventoryList ;
rptrMain.ItemDataBound += new RepeaterItemEventHandler(rptrMain_ItemDataBound);
rptrMain.DataBind();

void rptrMain_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
    if(e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
    {
        Inventory inventory = e.Item.DataItem as Inventory;
        Label lblName = e.Item.FindControl("lblName") as Label;
        Label lblDescription = e.Item.FindControl("lblDescription") as Label;

        lblName.Text = inventory.Name;
        lblDescription.Text = inventory.Description;

        Repeater rptrSub = e.Item.FindControl("rptrSub") as Repeater;
        rptrSub.DataSource = inventory.Parts;
        rptrSub.ItemDataBound += new RepeaterItemEventHandler(rptrSub_ItemDataBound);
        rptrSub.DataBind();
    }
}

void rptrSub_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
    if(e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
    {
        Part part = e.Item.DataItem as Part;
        Label lblPartName = e.Item.FindControl("lblPartName ") as Label;
        Label lblManufacturerName = e.Item.FindControl("lblManufacturerName") as Label;

        lblPartName.Text = part.Name;
        lblManufacturerName.Text = part.Manufacturer.Name
    }
}

库存与零件有1对多的关系，而零件与制造商有多对一的关系。

现在我的问题是：如何在LINQ查询中过滤Inventory的子实体？例如，我只想检索某个PartType的所有零件。像这样：

where parts.Type == Tire

我确实找到了这个有用的提示http://blogs.msdn.com/b/alexj/archive/2009/06/02/tip-22-how-to-make-include-really-include.aspx 虽然那仍然不允许我过滤子实体？

Answer 1

我认为最好的方法是在调用DataBind（）之前过滤用于rptrMain的数据源。例如，代码可能是这样的：

var q = from inventories in itemContext.Inventory.Include("Parts.Manufacturer")
        where inventories.Part.Type == Tire
        select inventories;
...

在第一条评论后编辑：

我声明了两个新类，包括格式化查询所需的字段：

class AbstractPartsClass
{
    public string Name { get; set; }
    public string ManufacturerName { get; set; }
}
class AbstractInventoryClass
{
    public string Name { get; set; }
    public string Description { get; set; }
    public List<AbstractPartsClass> AbstractParts { get; set; }
}

然后我更改了查询和部分代码，如下所示：

var q = from inventory in itemContext.Inventory.Include("Parts.Manufacturer")
        let filteredParts = from part in inventory.Parts
                            where part.Type == Tire //any filter condition
                            select new AbstractPartsClass()
                            {
                                Name = part.Name,
                                ManufacturerName = part.ManufacturerName
                            }
        select new AbstractInventoryClass()
        {
            Name = inventory.Name,
            Description = inventory.Description,
            AbstractParts = filteredParts.ToList(),
        };
List<AbstractInventoryClass> inventoryList = q.ToList();
rptrMain.DataSource = inventoryList ;
rptrMain.ItemDataBound += new RepeaterItemEventHandler(rptrMain_ItemDataBound);
rptrMain.DataBind();

void rptrMain_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
    if(e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
    {
        Inventory inventory = e.Item.DataItem as AbstractInventoryClass; //changed line
        Label lblName = e.Item.FindControl("lblName") as Label;
        Label lblDescription = e.Item.FindControl("lblDescription") as Label;

        lblName.Text = inventory.Name;
        lblDescription.Text = inventory.Description;

        Repeater rptrSub = e.Item.FindControl("rptrSub") as Repeater;
        rptrSub.DataSource = inventory.AbstractParts; //changed line
        rptrSub.ItemDataBound += new RepeaterItemEventHandler(rptrSub_ItemDataBound);
        rptrSub.DataBind();
    }
}
void rptrSub_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
    if(e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
    {
        Part part = e.Item.DataItem as AbstractPartsClass; //changed line
        Label lblPartName = e.Item.FindControl("lblPartName ") as Label;
        Label lblManufacturerName = e.Item.FindControl("lblManufacturerName") as Label;

        lblPartName.Text = part.Name;
        lblManufacturerName.Text = part.ManufacturerName
    }
}

如何在LINQ Include查询中过滤子实体？

1 个答案:

在第一条评论后编辑：