C＃lambda，僅限月份選擇.Distinct（）或GroupBy（）？

Question

我有以下

protected void Page_Load(object sender, EventArgs e) 
{ 
    DataX dx = new DataX(); 
    List<Excursion> lstExcur = new List<Excursion>(); 
    lstExcur = dx.GetAllExcursions(); 
    rptExcursionOuter.DataSource = lstExcur.Distinct(x => x.StartDate.Month); 
    rptExcursionOuter.DataBind(); 
} 
protected void rptExcursionOuter_ItemDataBound(object sender, RepeaterItemEventArgs e) 
{ 
    if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) 
    { 
     if (e.Item.DataItem != null) 
     { 
      Excursion Ritem = (Excursion)e.Item.DataItem;//<---- this bit errors, is there a way to keep the object intact but group or distinct by month? 
      Literal LitExcursionMonth = (Literal)e.Item.FindControl("LitExcursionMonth"); 
      LitExcursionMonth.Text = Ritem.StartDate.ToString("MMMM"); 
     } 
    } 
} 

有沒有一種方法可以讓我GROUPBY或一個月曆歷選擇但它retunr對象，所以我可以給的ItemDataBound DataItem的？ 任何幫助都會大大降低。

Answer 1

先做GroupBy得到一個IEnumerable<IGrouping<int, Excursion>>其中int是Excursion.StartDate.Month：

rptExcursionOuter.DataSource = lstExcur.GroupBy(x => x.StartDate.Month, x => x) 
             .OrderBy(g => g.First().StartDate.Month); 

更改下面的方法：

protected void rptExcursionOuter_ItemDataBound(object sender, RepeaterItemEventArgs e) 
{ 
    if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) 
    { 
     if (e.Item.DataItem != null) 
     { 
      var itemsByMonth = (IGrouping<int, Excursion>)e.Item.DataItem; 
      Literal LitExcursionMonth = (Literal)e.Item.FindControl("LitExcursionMonth"); 
      LitExcursionMonth.Text = itemsByMonth.First().StartDate.ToString("MMMM"); 
     } 
    } 
} 

更新：增加了排序依據