有时候我们想实现 leftJoin 但是 Linq 提供的 Join 相当于是INNER JOIN,于是就打算实现一个LeftJoin的扩展。 如果要使用到左连接,你需要使用 DefaultIfEmpty 来在没有join到数据的时候返回默认的集合 Solution 源代码:https://github.com/WeihanLi/WeihanLi.Common/blob/dev/src
LEFT OUTER JOIN [OrderDetail] AS [t1] ON [t0].[ProductID]=[t1].[ProductID] Linq Query:frompinProducts join odinOrderDetails on p.ProductID equals od.ProductID into uiofromoinuio.DefaultIfEmpty()selectnew{ p.ProductName, o.TotalPrice } Linq Method: Products .GroupJoin ( OrderDetails, p...
var leftJoinSql = from student in db.Student join book in db.Book on student.ID equals book.StudentID into temp from tt in temp.DefaultIfEmpty() select new { sname= , bname = tt==null?""://这里主要第二个集合有可能为空。需要判断 }; 1. 2. 3. 4. 5. 6. 7. 8. 9. 用Linq实...
默认情况下,GroupJoin 执行与左外部联接left outer join等效的操作。要获得内部联接inner join(从而排除没有购买的客户),您需要过滤 custPurchases: fromcincustomersjoinpinpurchasesonc.IDequalsp.CustomerIDintocustPurchaseswherecustPurchases.Any()select... group-joininto之后的子句对内部子元素的子序列进行操作,而...
} static void TestByLinqMethod() { Console.WriteLine("\nQuery #1 start:"); ...
https://docs.microsoft.com/en-us/dotnet/framework/data/adonet/ef/language-reference/method-based-query-syntax-examples-join-operators** **Perform left outer joinshttps://docs.microsoft.com/en-us/dotnet/csharp/linq/perform-left-outer-joins** **...
This limitation no longer exists: when StreamInsight encounters an unrecognized method (e.g. LeftOuterJoin in the above example) returning a stream definition, it will invoke the method to see what it returns, on the grounds that doing so may be better than failing. The examples in this ...
();privateOrganizationServiceProxy _serviceProxy;privateIOrganizationService _service;#endregionClass Level Members#regionHow To Sample Code//////This method first connects to the Organization service. Afterwards,///basic LINQ queries are performed.//////Contains server connection information.///When ...
Because there's no directly "right join" for the linq, so you must use "left join" but reverse the two tables, and the use DefaultIfEmpty() method, here's the sample to tip you: public class CompareTest { class T1 { public int DataId { get; set; } public int FDataId { get; ...
Self-join Double and multiple joins Join using entity fields Late-binding left join Use the Equals operator Use the Not Equals operator Use a method-based LINQ query with a Where clause Use the Greater Than operator Use the Greater Than or Equals and Less Than or Equals operators ...