LINQ GROUPBY月，并添加任何缺少个月来的分组数据 [英] linq groupby Months and add any missing months to the grouped data

问题描述

我创建这似乎是工作确定一个LINQ声明。我可能会或maynot正确写它不过其返回我的预期结果。

I have created a linq statement which seems to be working ok. I may or maynot have written it correctly however its returning my expected results.

     var grouped = RewardTransctions.GroupBy(t => new
        {
            t.PurchaseDate.Value.Month
        }).Select(g => new TransactionDetail()
        {
            Month =
                g.Where(w=>w.EntryType==1).Select(
                    (n =>
                     n.PurchaseDate.Value.Month))
                .First(),
            TransactionAmount = g.Count()
        });

现在的结果返回由分组月5值。是否有可能与TransactionAmount = 0，将它们添加7个其他失踪月？

Now the results are returning 5 values grouped by months. Is it possible to add the 7 other missing months with a TransactionAmount = 0 to them?

原因我的疯狂是我想这些值绑定到一个图表，根据个月有我的X轴。目前其仅示出了5个月的记录。如果我的数据犯规一个月我一定要怎么在0值添加返回任意值。

The reason for my madness is I am trying to bind these values to a chart and having my x axis based on months. Currently its only showing the 5 months of records. If my data doesnt return any value for a month I some how want to add in the 0 value.

有什么建议？

推荐答案

如果你使用它很简单 .ToLookup（...）。

var lookup =
    (from w in RewardTransctions
     where w.EntryType == 1
     select w).ToLookup(w => w.PurchaseDate.Value.Month);

var grouped =
    from m in Enumerable.Range(1, 12)
    select new TransactionDetail()
    {
        Month = m,
        TransactionAmount = lookup[m].Count(),
    };

是如何形成的几个简单的LINQ查询的？

How's that for a couple of simple LINQ queries?

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