2024年5月7日 · Query Syntax for LINQ Join. var productOrderQuery = from product in Product.Setup()//outer sequence join ...

2013年3月21日 · To join on multiple field in LINQ, you have to create a new anonymous type containing the columns you want ...

Is it possible in LINQ to join on multiple fields in a single join? EDIT. var result = from x in entity join y in entity2 on new { x.field1, x.field2 } equals new { y.field1, y.field2 } is the solution I referenced as assuming an equijoin above. Further EDIT

2008年9月1日 · basically LINQ join operator provides no benefit for SQL. I.e. the following query. var r = from dealer in db.Dealers from contact in db.DealerContact where dealer.DealerID == contact.DealerID select dealerContact; will result in INNER JOIN in SQL. join is useful for IEnumerable<> because it is more efficient: from contact in db.DealerContact

Justin has correctly shown the expansion in the case where the join is just followed by a select.If you've got something else, it becomes more tricky due to transparent identifiers - the mechanism the C# compiler uses to propagate the scope of both halves of the join.

2015年12月9日 · The Join method, which is called by the join clause in C#, implements an inner join. This topic shows you how to perform four variations of an inner join: A simple inner join that correlates elements from two data sources based on a simple key. An inner join that correlates elements from two data sources based on a composite key.

2014年4月11日 · I stress again, if you are doing that in Linq-2-Objects (instead of Linq-2-SQL), you should do it the old-fashioned way (because LINQ to SQL translates this correctly to join operations, but over objects this method forces a full scan).

2019年10月18日 · Assuming that you still require a left join; here's how you do a left join in Linq: var results = from data in userData join growth in userGrowth on data.User equals growth.User into joined from j in joined.DefaultIfEmpty() select new { UserData = data, UserGrowth = j };

2009年2月8日 · Using extension syntax I'm trying to create a left-join using LINQ on two lists that I have. The following is from the Microsoft help but I've modified it to show that the pets list has no elements. What I'm ending up with is a list of 0 elements. I assume that this is because an inner-join is taking place.

2015年4月15日 · One option is to do some custom join combined with left joins. A decent TSQL backend should not get any drawbacks in terms of performance for always using all the joins, since the optimers would just remove the join if the condition is always false.