如何在C＃LINQ查詢中使用Distinct運算符

Question

我想使用c＃中的以下代碼選擇唯一的EventYear，它給出重復的值。 我的表(EventMasters)結構是(EventYear (string), EventCode, EventDescription)我想選擇唯一或不同的EventYear

    public ActionResult EventYearsMenu()
    {
        var eventyears = storeDB.EventMasters.Distinct().ToList().OrderByDescending(c => c.EventYear== c.EventYear.Distinct());
        return PartialView(eventyears);
    }

Answer 1

我想選擇唯一或不同的EventYear

不只是：

var eventyears = storeDB.EventMasters
                        .Select(c => c.EventYear)
                        .Distinct()
                        .ToList();

Answer 2

這樣嘗試

var eventyears = from Data in storeDB.EventMasters
                         where (this == that) // Write your Logic
                         select Data;

        if (eventyears != null)
        {
            /// do your code,,.,,,
        }

Answer 3

嘗試跟隨

var eventyears = storeDB.EventMasters
                     .GroupBy(c=>c.EventYear)
                     .Select(items=>items.First())
                     .SelectMany(item->item)
                       .ToList()
                       .OrderByDescending(c => c.EventYear == c.EventYear.Distinct());

它將采用不同的項目（基於EventYear）。 （即使EventYear相同的項目在某些其他屬性上具有不同的值，也可能將其歸類為相同的項目）

Answer 4

嘗試這個

var eventyears = storeDB.EventMasters.ToList()
                       .OrderByDescending(c => c.EventYear == c.EventYear).Distinct();

Answer 5

您可以嘗試此代碼。

var eventyears = storeDB.EventMasters.Distinct(q => q.EventYear.).ToList().OrderByDescending(c => c.EventYear);

return PartialView(eventyears);