如何在linq中使用group by

Question

我有一个新闻转发器,显示两个字段,如News_Text和News_Date.

在这里,我只想用group by显示这些数据News_date.

喜欢:

12/24/2013
test
test1
test 2

11/12/213
blah..blah

这是我的代码:

private void BindNewsRepeater()
    {
        using (DataClassesDataContext db = new DataClassesDataContext())
        {
            var query = from n in db.News
                        orderby n.News_date descending
                        select new 
                    {
                         News_text = n.News_text,
                         News_date = n.News_date
                    };

            DataSet myDataSet = new DataSet();
            DataTable dt = new DataTable();
            dt.Columns.Add(new DataColumn("News_text", typeof(string)));
            dt.Columns.Add(new DataColumn("News_date", typeof(string)));
            foreach (var item in query)
            {
                DataRow dr = dt.NewRow();
                dr["News_text"] = item.News_text.ToString();
                dr["News_date"] = item.News_date.ToString("dd/MM/yyyy");
                dt.Rows.Add(dr);
            }
            myDataSet.Tables.Add(dt);
            rpt_news.DataSource = myDataSet;
            rpt_news.DataBind();
        }
    } 

我的中继器设计代码是:

<asp:Repeater ID="rpt_news" runat="server" onitemdatabound="rpt_news_ItemDataBound">
     <ItemTemplate><asp:Label ID="lbl_news_date" runat="server"><%#Eval("News_date")%></asp:Label><br />
                                            <asp:Label ID="lbl_news_text" runat="server"><%#Eval("News_text")%></asp:Label>
                                            </ItemTemplate>
                                            <SeparatorTemplate><br/><br/></SeparatorTemplate>
     </asp:Repeater>

Answer 1

您可以简单地GroupBy News_date选择News_date列表中的每个键News_Text.像这样的东西:

var results = News
    .GroupBy(n => n.News_date)
    .Select(g => new {
        NewsDate = g.Key,
        NewsTexts = g.Select(x => x.News_Text)
    });

这将返回News_Text每个列表NewsDate.