使用 LINQ 的条件分组依据语句答案

【问题标题】：Conditional Group By statement using LINQ使用 LINQ 的条件分组依据语句
【发布时间】：2010-11-01 05:52:43
【问题描述】：

我有一个看似相当简单的要求，但环顾四周，我无法得到一个简单的答案。我看过 MSDN 论坛、Exper Exchange 并没有给我任何实质性的东西。

我有以下 LINQ 代码

Dim SummaryLog As IQueryable(Of clPartCountSummary)    
SummaryLog = From Inventory In db.tblPartCounts _
            Where Inventory.InventoryCountId = InventoryCountId _
            And Not Inventory.ActionId.HasValue _
            Group By PartNumber = Inventory.PartNumber _
            , Inventory.RevLevel, SAPLocation = Inventory.SAPLocation _
            Into AggregatedProdLog = Group, Qty = Sum(Inventory.Quantity) _
            Select New clPartCountSummary With 
                {.PartNumber = PartNumber, 
                 .RevLevel = RevLevel, 
                 .Qty = Qty, 
                 .SAPLocation = SAPLocation}

我希望能够按RevLevel 和SAPLocation 有条件地分组。我将始终按PartNumber 分组，但其他两个是可选的。因此，如果变量bRevLevel 为真，则我们按RevLevel 分组，如果bSAPLocation 为真，则我们也按SAPLocation 分组。

任何帮助将不胜感激，我正处于多个 SummaryLog 定义开始看起来很有吸引力的阶段。

谢谢，托马斯

【问题讨论】：

标签： c# linq if-statement group-by conditional

【解决方案1】：

希望这会有所帮助....

public class TblPartCount
{
    public int InventoryCountID { get; set; }
    public int? ActionID { get; set; }
    public string PartNumber { get; set; }
    public int RevLevel { get; set; }
    public string SAPLocation { get; set; }
    public int Quantity { get; set; }
}

private static void ConditionalGroupBy()
    {
        bool pCheck = true;

        var lList = new List<TblPartCount>
                        {
                            new TblPartCount { InventoryCountID = 1, ActionID = 2, PartNumber = "123", RevLevel = 1, SAPLocation = "AAAA", Quantity = 100 },
                            new TblPartCount { InventoryCountID = 1, ActionID = 2, PartNumber = "123", RevLevel = 1, SAPLocation = "BBBB", Quantity = 200 }
                        };

        var lOutput = lList
                          .Where(pArg => pArg.InventoryCountID == 1)
                          .Where(pArg => pArg.ActionID != null)
                          .GroupBy(pArg => new
                          {
                              PartNumber = pArg.PartNumber,
                              RevLevel = pCheck ? pArg.RevLevel : 0,
                              SAPLocation = pCheck ? pArg.SAPLocation : String.Empty
                          })
                          .Select(pArg =>
                                    new
                                    {
                                        PartNumber = pArg.Key.PartNumber,
                                        RevLevel = pArg.Key.RevLevel,
                                        SAPLocation = pArg.Key.SAPLocation,
                                        Qtry = pArg.Sum(pArg1 => pArg1.Quantity)
                                    });

        foreach (var lItem in lOutput)
        {
            Console.WriteLine(lItem);
        }
    }

【讨论】：