LINQ Lambda Group By Sum

嗨，我可以在方法语法中这样做，但我正在努力提高我的lambda技能我该怎么办：

SELECT SUM([job_group_quota]) as 'SUM' FROM [dbo].[tbl_job_session] WHERE [job_group_job_number] = @jobnum and [job_group_ID] like @sess GROUP BY [job_group_job_number] 

我一直在搞乱它，但无法做到正确。

 lnq.tbl_job_sessions.GroupBy(a => a.job_group_job_number == jnum) .Select(b => new { b.job_group_quota}).Sum(); 

Answer 1

一般例子：

 query .GroupBy(item => item.GroupKey) .Select(group => group.Sum(item => item.Aggregate)); 

Answer 2

几个小组的例子

public void GroupBy1（）{var personList = dbEntities.People.GroupBy（m => m.PersonType）.Select（m => new {PersonType = m.Key，Count = m.Count（）}）; }

  public void GroupBy2() { var personList = dbEntities.People.GroupBy(m => new { m.PersonType, m.FirstName }).Select(m => new { PersonType = m.Key, Count = m.Count() }); } public void GroupBy3() { var personList = dbEntities.People.Where(m => m.EmailPromotion != 0).GroupBy(m => new { m.PersonType, m.FirstName }).Select(m => new { PersonType = m.Key, Count = m.Count() }); } public void GroupBy4() { var personList = dbEntities.People.GroupBy(m => new { m.PersonType, m.FirstName }).Where(m => m.Count() > 70).Select(m => new { PersonType = m.Key, Count = m.Count() }); } public void GroupBy5() { var personList = dbEntities.People .GroupBy(m => new { m.PersonType }).Where(m => m.Count() > 70) .Select(m => new { PersonType = m.Key, Count = m.Count() }); var list1 = dbEntities.People. GroupBy(m => new { m.PersonType }). Select(m => new { Type = m.Key, Count = m.Count() }) .Where( m => m.Count > 70 && m.Type.PersonType.Equals("EM") || m.Type.PersonType.Equals("GC")); } public void GroupBy6() { var list1 = dbEntities.People. GroupBy(m => new { m.PersonType, m.EmailPromotion }).Select(m => new { Type = m.Key, Count = m.Count() }) .Where ( m => m.Count > 70 && m.Type.EmailPromotion.Equals(0) && ( m.Type.PersonType.Equals("EM") || m.Type.PersonType.Equals("GC") )); } public void GroupBy7() { var list1 = dbEntities.People. GroupBy(m => m.PersonType). Select(c => new { Type = c.Key, Total = c.Sum(p => p.BusinessEntityID) }); } public void GroupBy8() { var list1 = dbEntities.People. GroupBy(m => m.PersonType). Select(c => new { Type = c.Key, Count = c.Count(), Total = c.Sum(p => p.BusinessEntityID) }); } public void GroupBy9() { var list1 = dbEntities.People. GroupBy(m => m.PersonType). Select(c => new { Type = c.Key, Max = c.Max(), }); } 

Answer 3

此示例显示如何迭代获取键和总计的分组值，以及如何直接获取总计（如前所述）。 两者都只使用lambda运算符。

 using System; using System.Collections.Generic; using System.Linq; public class Person { public string Name { get; set; } public string City { get; set; } public string ZipCode { get; set; } public int SomeValue { get; set; } } class Program { static void Main(string[] args) { List data = GetPopulatedData(); var totals = data.GroupBy(x => new { x.Name, x.City, x.ZipCode }).Select(y => y.Sum(i => i.SomeValue)); var groupsForIterate = data.GroupBy(x => new { x.Name, x.City, x.ZipCode }); Console.WriteLine("Totals: "); foreach (var total in totals) { Console.WriteLine(total); } Console.WriteLine("Categories: "); foreach (var categ in groupsForIterate) { // You can refer to one field like this: categ.Key.Ciduad Console.WriteLine("Group" + categ.Key); Console.WriteLine(categ.Sum(x => x.SomeValue)); } //Output: //Totals: //1 //2 //1 //Categories: //Group{ Name = Mark, City = BCN, ZipCode = 00000 } //1 //Group{ Name = Mark, City = BCN, ZipCode = 000000 } //2 //Group{ Name = John, City = NYC, ZipCode = 000000 } //1 } private static List GetPopulatedData() { List datos = new List() { new Person(){Name="Mark", City = "BCN", ZipCode = "00000", SomeValue = 1}, // group A new Person(){Name="Mark", City = "BCN", ZipCode = "000000", SomeValue = 1}, // group B new Person(){Name="Mark", City = "BCN", ZipCode = "000000", SomeValue = 1}, // group B new Person(){Name="John", City = "NYC", ZipCode = "000000", SomeValue = 1}, // group C }; return datos; } }