Question

我已经浏览过StackOverlow，但未能就此找到明确的答案。

下面我有一个我目前拥有的代码片段，我将解释我想要实现的目标。

Table<Gallery> galleries = pdc.GetTable<Gallery>();
Table<GalleryImage> images = pdc.GetTable<GalleryImage>();
Table<Comment> comments = pdc.GetTable<Comment>();

var query = from gallery in galleries
            join image in images on gallery.id equals image.galleryid into joinedimages
            join comment in comments on gallery.id equals comment.galleryid into joinedcomments
            select gallery;

gallst.DataSource = query;
gallst.DataBind();

从上面我有以下转发器：

<asp:Repeater ID="gallst" runat="server" EnableViewState="false">
    <HeaderTemplate>
        <div id="gallery">
    </HeaderTemplate>
    <ItemTemplate>
        <div class="item">
            <h2><%# DataBinder.Eval(Container.DataItem, "name") %> @ <%# DataBinder.Eval(Container.DataItem, "wheretaken") %></h2>
            <ul class="images">
            <asp:Repeater ID="galimgs" runat="server" EnableViewState="false" DataSource='<%# Eval("GalleryImages") %>'>
                <ItemTemplate>
                    <li><a href="<%# DataBinder.Eval(Container.DataItem, "image") %>.jpg" title="<%# DataBinder.Eval(((System.Web.UI.WebControls.RepeaterItem)Container.Parent.Parent).DataItem, "name") %>" rel="prettyPhoto[<%# DataBinder.Eval(Container.DataItem, "galleryid")%>]" class="thickbox"><img src="<%# DataBinder.Eval(Container.DataItem, "image") %>_thumb.jpg" /></a></li>
                </ItemTemplate>
            </asp:Repeater>
            </ul>
            <div class="comments">
            <asp:Repeater ID="galcomments" runat="server" EnableViewState="false" DataSource='<%# Eval("Comments") %>'>
                <HeaderTemplate>
                    <ul>
                </HeaderTemplate>
                <ItemTemplate>
                    <li><%# GetUserName(new Guid(Eval("userid").ToString())) %> said: <%#DataBinder.Eval(Container.DataItem, "comment1") %> (<%# DataBinder.Eval(Container.DataItem, "date", "{0:dddd  MM, yyyy hh:mm tt}") %>)</li>
                </ItemTemplate>
                <FooterTemplate>
                    </ul>
                </FooterTemplate>
            </asp:Repeater>
            <uc:makecomment ID="mcomment" runat="server" PhotoID='<%# DataBinder.Eval(Container.DataItem, "id") %>'></uc:makecomment>
        </div>
        </div>
    </ItemTemplate>
    <FooterTemplate>
        </div>
    </FooterTemplate>
</asp:Repeater>

我想做的（理想情况下）只是为每个画廊拍摄前3个评论。

我尝试了以下LINQ查询但没有运气：

var query = from gallery in galleries
            join image in images on gallery.id equals image.galleryid into joinedimages
            join comment in comments.Take(3) on gallery.id equals comment.galleryid into joinedcomments
            select gallery;

有没有人对如何实现这一点有任何建议？

Answer 1

这看起来可能是您需要的调整。它来自一个非常有用的LINQ示例站点。

此sample打印华盛顿客户的前三个订单的客户ID，订单ID和订单日期。该示例使用Take将查询表达式生成的序列限制为前三个订单。

public void Linq21() {
            List<Customer> customers = GetCustomerList();


        var first3WAOrders = (
            from c in customers
            from o in c.Orders
            where c.Region == "WA"
            select new {c.CustomerID, o.OrderID, o.OrderDate} )
            .Take(3);

        Console.WriteLine("First 3 orders in WA:");
        foreach (var order in first3WAOrders) {
            ObjectDumper.Write(order);
        }
    }

结果

西澳州的前3个订单：

CustomerID=LAZYK OrderID=10482 OrderDate=3/21/1997

CustomerID=LAZYK OrderID=10545 OrderDate=5/22/1997

CustomerID=TRAIH OrderID=10574 OrderDate=6/19/1997

Answer 2

我设法让它与之合作：

        Table<Gallery> galleries = pdc.GetTable<Gallery>();
        Table<GalleryImage> images = pdc.GetTable<GalleryImage>();
        Table<Comment> comments = pdc.GetTable<Comment>();

        var query = from gallery in galleries
                    join image in images on gallery.id equals image.galleryid into joinedimages
                    join comment in comments on gallery.id equals comment.galleryid into joinedcomments
                    select new
                    {
                        name = gallery.name,
                        wheretaken = gallery.wheretaken,
                        id = gallery.id,
                        GalleryImages = joinedimages,
                        Comments = joinedcomments.Take(3)
                    };

        gallst.DataSource = query;
        gallst.DataBind();

随着选择的发生。谢谢大家的帮助。关于如何写这个“更好”的任何建议都将不胜感激。

使用LinqtoSql加入，只在连接表上选择TOP（x）？

2 个答案: