LINQ 全联接 FULL JOIN （二）

最新推荐文章于 2024-11-29 07:00:00 发布

转载最新推荐文章于 2024-11-29 07:00:00 发布 · 267 阅读

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原文链接：http://www.cnblogs.com/xust/articles/2789088.html

本文详细介绍了如何使用C#编程语言实现全外连接，包括左外连接、右外连接和全外连接的实现方法及示例代码。

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 void FullOuterJoin()
        {
            var firstNames = new[]
                {
                    new { ID = 1, Name = "John" },
                    new { ID = 2, Name = "Sue" },
                };
            var lastNames = new[]
                {
                    new { ID = 1, Name = "Doe" },
                    new { ID = 3, Name = "Smith" },
                };
            var leftOuterJoin = from first in firstNames
                                join last in lastNames
                                on first.ID equals last.ID
                                into temp
                                from last in temp.DefaultIfEmpty(new { first.ID, Name = default(string) })
                                select new
                                {
                                    first.ID,
                                    FirstName = first.Name,
                                    LastName = last.Name,
                                };
            //var leftOuterJoin = from first in firstNames
            //                    join last in lastNames
            //                    on first.ID equals last.ID
            //                    into temp
            //                    from last in temp.DefaultIfEmpty()
            //                    select new
            //                    {
            //                        first.ID,
            //                        FirstName = first.Name,
            //                        LastName = last != null ? last.Name : default(string),
            //                    };
            var rightOuterJoin = from last in lastNames
                                 join first in firstNames
                                 on last.ID equals first.ID
                                 into temp
                                 from first in temp.DefaultIfEmpty(new { last.ID, Name = default(string) })
                                 select new
                                 {
                                     last.ID,
                                     FirstName = first.Name,
                                     LastName = last.Name,
                                 };
            var fullOuterJoin = leftOuterJoin.Union(rightOuterJoin);
        }

转载于:https://www.cnblogs.com/xust/articles/2789088.html