具有多个级别的对象上的LINQ GroupBy

本文关键字：对象 LINQ GroupBy | 更新日期: 2023-09-27 18:24:54

我有一些类声明如下：

public class UserSpend
{
    public string UserName{ get; set; }
    public MonthSpend[] Spend { get; set; }
}
public class MonthSpend
{
    public DateTime Month { get; set; }
    public SpendDetail[] Detail { get; set; }
}
public class SpendDetail
{
    public string Description { get; set; }
    public decimal Amount { get; set; }
}

正如你所看到的，它有几个层次。我已经声明了这样一个变量：

UserSpend[] allSpend;

我填充了它，这样我就有了几个UserSpend，每个UserSpend都有几个MonthSpend，它们都有几个SpendDetail。所以数据看起来像这样：

allSpend =
UserSpend (UserName = "Bob", Spend = [
        MonthSpend (Month = "01/09/12", Detail = [
            SpendDetail (Description = "Local", Amount = "12.00"),
            SpendDetail (Description = "National", Amount = "7.00") ]
        MonthSpend (Month = "01/10/12", Detail = [
            SpendDetail (Description = "Local", Amount = "8.00"),
            SpendDetail (Description = "Mobile", Amount = "3.00"),
            SpendDetail (Description = "National", Amount = "15.00") ]
        MonthSpend (Month = "01/11/12", Detail = [
            SpendDetail (Description = "Local", Amount = "16.00"),
            SpendDetail (Description = "National", Amount = "5.00") ] ]
UserSpend (UserName = "Jack", Spend = [
        MonthSpend (Month = "01/09/12", Detail = [
            SpendDetail (Description = "Local", Amount = "1.00"),
            SpendDetail (Description = "National", Amount = "4.00"),
            SpendDetail (Description = "International", Amount = "17.00") ]
        MonthSpend (Month = "01/10/12", Detail = [
            SpendDetail (Description = "Local", Amount = "2.00"),
            SpendDetail (Description = "Mobile", Amount = "7.00"),
            SpendDetail (Description = "International", Amount = "5.00") ]
        MonthSpend (Month = "01/11/12", Detail = [
            SpendDetail (Description = "Local", Amount = "6.00"),
            SpendDetail (Description = "National", Amount = "2.00") ] ]

我想做的是填充这个变量：

public class UserDataPoint
{
    public string User { get; set; }
    public string Category { get; set; }
    public int Spend { get; set; }
}
UserDataPoint[] userData;

以便userData包含这样的内容：

userData = UserDataPoint (
[User = "Bob", Category = "Local", Spend = 36.00]
[User = "Bob", Category = "Mobile", Spend = 3.00]
[User = "Bob", Category = "National", Spend = 27.00]
[User = "Jack", Category = "Local", Spend = 9.00]
[User = "Jack", Category = "Mobile", Spend = 6.00]
[User = "Jack", Category = "National", Spend = 7.00]
[User = "Jack", Category = "International", Spend = 22.00]

因此，对于每个用户名，我想按描述进行分组，并求和金额。我正在尝试学习LINQ，并一直在尝试使用GroupBy来实现这一点，但我没有取得任何进展。请有人提供一个如何实现这一目标的例子。非常感谢，科林。

具有多个级别的对象上的LINQ GroupBy

使用LINQ中的语法查询：

userData = from spend in allSpend
           from monthSpend in spend.Spend
           from spendDetail in monthSpend.Detail
           group spendDetail by new {spend, spendDetail.Description} into g
           select new UserDataPoint
           {
               User = g.Key.spend.UserName,
               Category = g.Key.Description,
               Spend = g.Sum(t => t.Amount)
           };

这里的困难在于按多个列（用户名和类别）进行分组。这是在group ... by {spend, spendDetail.Description}中使用匿名类型完成的。参见堆叠溢出

更新

这里有一个更好的版本（不需要复杂的GroupBy）：

userData = from spend in allSpend
           from userDataPoint in
               (from monthSpend in spend.Spend
               from spendDetail in monthSpend.Detail
               group spendDetail by spendDetail.Description into g
               select new UserDataPoint
               {
                   User = spend.UserName,
                   Category = g.Key,
                   Spend = g.Sum(t => t.Amount)
               })
           select userDataPoint;
相关文章：