按月分组计数

Question

我正在尝试返回一个月内有多少客户“注册”的结果。目前它返回每个特定日期的计数。见下文：

这是我的控制器中的代码：

 public ActionResult About()
        {
            IQueryable<EnrollmentDateGroup> data = from customer in db.Customers
                                                   group customer by customer.EnrollmentDate  into dateGroup

                                                   select new EnrollmentDateGroup()
                                                   {
                                                       EnrollmentDate = dateGroup.Key,
                                                       CustomerCount = dateGroup.Count() 

        };

谁能建议我如何计算每月注册的客户数量？

提前致谢。

更新

使用时出现如下错误：

group customer by new { customer.EnrollmentDate.Year, customer.EnrollmentDate.Month } into dateGroup

Answer 1

您需要单独按月和年分组。当您传递完整日期时，它包含一个会打乱分组的日期组件。例如：

group customer by new { Year = customer.EnrollmentDate.Year, Month = customer.EnrollmentDate.Month }

更新

这是因为您要将密钥直接设置为您的 EnrollmentDate 属性，而密钥现在是匿名类型，而不是 DateTime。要么创建一个DateTime，要么做一些不同的事情。

EnrollmentDate = new DateTime(m.Key.Year, m.Key.Month, 1),

Answer 2

在 GROUPBY 子句中使用强制转换

GROUP BY CAST(MONTH(date) AS VARCHAR(2)) + '-' + CAST(YEAR(date) AS VARCHAR(4))

Answer 3

试试这个。

var result = from s in data
             group s by new { date = new DateTime(s.EnrollmentDate.Year, s.EnrollmentDate.Month, 1)} into g 
select new {
date = g.Key.date,
Sum = g.Sum(x=>x.CustomerCount)
};