C# List<> GroupBy 2 值
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C# List<> GroupBy 2 Values
提问by SaaS Developer
I'm using C# on Framework 3.5. I'm looking to quickly group a Generic List<> by two properties. For the sake of this example lets say I have a List of an Order type with properties of CustomerId, ProductId, and ProductCount. How would I get the sum of ProductCounts grouped by CustomerId and ProductId using a lambda expression?
我在 Framework 3.5 上使用 C#。我希望通过两个属性快速将 Generic List<> 分组。就本示例而言，假设我有一个 Order 类型的 List，其中包含 CustomerId、ProductId 和 ProductCount 的属性。如何使用 lambda 表达式获得按 CustomerId 和 ProductId 分组的 ProductCounts 的总和？
采纳答案by Jimmy
var sums = Orders.GroupBy(x => new { x.CustomerID, x.ProductID })
.Select(group => group.Sum(x => x.ProductCount));
回答by Klas Mellbourn
Alternatively, if you want to get the IDs for each sum, you could do this
或者，如果您想获取每个总和的 ID，您可以这样做
var customerAndProductGroups =
from order in Orders
orderby order.CustomerID, order.ProductID // orderby not necessary, but neater
group order by new { order.CustomerID, order.ProductID };
foreach (var customerAndProductGroup in customerAndProductGroups)
{
Console.WriteLine("Customer {0} has ordered product {1} for a total count of {2}",
customerAndProductGroup.Key.CustomerID,
customerAndProductGroup.Key.ProductID,
customerAndProductGroup.Sum(item => item.ProductCount));
}
回答by Todd Langdon
I realize this thread is very old but since I just struggled through this syntax I thought I'd post my additional findings - you can return the sum and the IDs (w/o foreach) in one query like so:
我意识到这个线程很老了，但由于我只是在这个语法中挣扎，我想我会发布我的其他发现 - 您可以在一个查询中返回总和和 ID（不带 foreach），如下所示：
var sums = Orders
.GroupBy(x => new { x.CustomerID, x.ProductID })
.Select(group =>new {group.Key, ProductCount = group.Sum(x => x.ProductCount)});
The tricky part for me to get it working is that the sum must be aliased, apparently...
我让它工作的棘手部分是总和必须是别名，显然......
回答by AnshuMan SrivAstav
var New1 = EmpList.GroupBy(z => z.Age).OrderBy(Employee => Employee.Key);
var New1 = EmpList.GroupBy(z => z.Age).OrderBy(Employee => Employee.Key);
dataGridView1.DataSource = New1;
dataGridView1.DataSource = New1;
