LINQ的嵌套组

我无法使用LINQ查询解决此问题。

所以我们有如下表结构：Id || bug_category || bug_name || bug_details || bug_priority

我想先通过bug_category进行分组。 对于每个bug_category，我想反过来按bug_priority分组。

基本上我想要的东西是这样的：

bug_category = AUDIO ::没有BUGS – > Critical = 3，Medium = 2和Low = 7个bug。
bug_category = VIDEO ::没有BUGS – > Critical = 5，Medium = 1和Low = 9个bug。

以下查询返回类别AND customer_priority的所有唯一组合：

（其中RawDataList只是具有上述结构的数据列表）

var ProceesedData = from d in RawDataList group d by new { d.bug_category, d.bug_priority } into g select new { g.Key.bug_category, g.Key.bug_priority }; 

以下查询返回该类别，后跟该类别中的记录列表：

  var ProceesedData = from d in RawDataList group d by d.bug_category into g select new { g.Key, records = g }; 

但是我无法继续进行，因为ProcessedData（返回变量）是一个未知类型。 有什么想法吗？

Answer 1

我怀疑你想要（名字改为更惯用）：

 var query = from bug in RawListData group bug by new { bug.Category, bug.Priority } into grouped select new { Category = grouped.Key.Category, Priority = grouped.Key.Priority, Count = grouped.Count() }; 

然后：

 foreach (var result in query) { Console.WriteLine("{0} - {1} - {2}", result.Category, result.Priority, result.Count); } 

或者（但稍后见）：

 var query = from bug in RawListData group bug by new bug.Category into grouped select new { Category = grouped.Category, Counts = from bug in grouped group bug by grouped.Priority into g2 select new { Priority = g2.Key, Count = g2.Count() } }; foreach (var result in query) { Console.WriteLine("{0}: ", result.Category); foreach (var subresult in result.Counts) { Console.WriteLine(" {0}: {1}", subresult.Priority, subresult.Count); } } 

编辑：如评论中所述，这将导致多个SQL查询。 要获得类似的结果结构但更有效，您可以使用：

 var dbQuery = from bug in RawListData group bug by new { bug.Category, bug.Priority } into grouped select new { Category = grouped.Key.Category, Priority = grouped.Key.Priority, Count = grouped.Count() }; var query = dbQuery.ToLookup(result => result.Category, result => new { result.Priority, result.Count }; foreach (var result in query) { Console.WriteLine("{0}: ", result.Key); foreach (var subresult in result) { Console.WriteLine(" {0}: {1}", subresult.Priority, subresult.Count); } } 

Answer 2

这是完成嵌套分组的更简单方法。 我已经在内存集合中对其进行了测试，无论您的特定数据库提供程序是否能够很好地处理它，或者它是否表现良好都是未知的。

假设您有两个属性，并希望按州和国家分组：

 var grouped = People .GroupBy(l => new { l.State, l.Country})//group by two things .GroupBy(l=> l.Key.Country)//this will become the outer grouping foreach(var country in grouped) { foreach(var state in country) { foreach(var personInState in state) { string description = $"Name: {personInState.Name}, State: {state.StateCode}, Country: {country.CountryCode}"; ... } } } 

Answer 3

我想你正在寻找类似的东西：

  var processedData = rawData.GroupBy(bugs => bugs.bug_category, (category, elements) => new { Category = category, Bugs = elements.GroupBy(bugs => bugs.bug_priority, (priority, realbugs) => new { Priority = priority, Count = realbugs.Count() }) }); foreach (var data in processedData) { Console.WriteLine(data.Category); foreach (var element in data.Bugs) Console.WriteLine(" " + element.Priority + " = " + element.Count); } 

Answer 4

你可以这样做

  var retList = (from dbc in db.Companies where dbc.IsVerified && dbc.SellsPCBs && !dbc.IsDeleted && !dbc.IsSpam && dbc.IsApproved select new { name = dbc.CompanyName, compID = dbc.CompanyID, state = dbc.State, city = dbc.City, businessType = dbc.BusinessType }).GroupBy(k => k.state).ToList(); List finalList = new List(); foreach (var item in retList) { finalList.Add(item.GroupBy(i => i.city)); }