Question

我有以下代码：

var checkRegisters = await Database.Client.Context.CheckRegister
            .Where(cr => cr.CheckingAccount == account 
                   && cr.CheckDate >= fromDate 
                   && cr.CheckDate <= toDate 
                   && cr.Void == "N" )
            .GroupBy(cr => cr.CheckNumber, 
                     cr => cr.Amount, (key, g) => 
                                          new { 
                                                CheckNumber = key, 
                                                Amount = g.Sum()
                                              })
            .OrderBy(c => c.CheckNumber)
            .ToListAsync();

除了向我返回CheckNumber和Amount的列表之外，我还不太了解它在做什么。 CheckRegister表包含Payee列，EF中的相应modelBuilder也包含：

entity.Property(e => e.Payee).HasColumnType("varchar(255)");

如何将收款人添加到返回的列表中？

Answer 1

代码的作用：

您的数据库有一个包含CheckRegisters的表。每个CheckRegister至少具有属性CheckingAccount，CheckDate，Void，CheckNumber和Amount，根据您的情况，它也具有属性{ {1}}：

因此，您的代码将逐步介绍。

Payee

现在您想要的更改：添加// Take the complete table of CheckRegisters: Database.Client.Context.CheckRegister // from every checkRegister in this table (every row), // keep only those checkRegisters that have a CheckingAccount value equal to account // and a CheckDate value betwen fromData and toDate // and a value for property Void equalt to "N" .Where(checkRegister => checkRegister.CheckingAccount == account && checkRegister.CheckDate >= fromDate && checkRegister.CheckDate <= toDate && checkRegister.Void == "N" ) // Group all remaining CheckRegisters into groups with same checkNumber // Each group will have a property Key which has the value of the common CheckNumber .GroupBy(cr => cr.CheckNumber, // ElementSelector: from every CheckRegister put only the amount in each grouop checkRegister => checkRegister.Amount, // ResultSelector: take every key (which we call checkNumber) // and all Amounts of all CheckRegisters with this CheckNumber // to make one new object: (checkNumber, amountsFromCheckRegistersWithThisCheckNumber) => new { CheckNumber = key, // To calculate property Amount: sum all amountsFromCheckRegistersWithThisCheckNumber Amount = amountsFromCheckRegistersWithThisCheckNumber.Sum(), }) // By now you have a sequence of objects, each with two properties: // CheckNumber: a checkNumber used in the CheckRegisters that were left after the Where // Amount: the sum of all Amounts of all CheckRegisters that have this CheckNumber // Finally you do some Ordering, and convert the resulting elements into a list .OrderBy(groupedItem => groupedItem.CheckNumber) .ToListAsync();。

问题是，返回的数据是按CheckNumber分组的CheckRegisters。每个收款人都是每个CheckRegister。如果将具有相同CheckNumber的CheckRegisters组组成，则可以使用此CheckNumber获得几位收款人：

Payees

如果我使用相同的CheckNumber进行分组，则会得到：

CheckNumber | Payee | ...
    1       |   A
    2       |   B
    1       |   C
    2       |   C    // note: C  is used again
    1       |   D

因此，每个组可能有不止一名员工。如果可以的话，只需省略ElementSelector并在ResultSelector中选择雇员

group CheckNumber 1 [1, A], [1,C], [1,D]
group CheckNumber 2 [2, B], [2,C]

Answer 2

我会将其添加到您在GroupBy中创建的对象中。因此，如下更改第3行

.GroupBy(cr => cr.CheckNumber, cr => cr.Amount, cr => cr.Payee, (key, g) => 
                              new { CheckNumber = key, Amount = g.Sum(), Payee = g.Payee})

请注意，分组依据只是按数字和金额分开，因此，如果您也按收款人分组，则应该预期结果列表会更长。这也假设收款人是表中列的名称。

Answer 3

通过以下方式将新列添加到组中：

var checkRegisters = await Database.Client.Context.CheckRegister
            .Where(cr => cr.CheckingAccount == account && cr.CheckDate >= fromDate && cr.CheckDate <= toDate && cr.Void == "N" )
            .GroupBy(cr => cr.CheckNumber, cr => cr.Amount, e => e.Payee , (key, g, p) => new { CheckNumber = key, Amount = g.Sum(), Payee = p})
            .OrderBy(c => c.CheckNumber).ToListAsync();

从LINQ添加附加值

3 个答案: