您提供的示例数据和输出未演示左连接。如果是左联接，您的输出将如下所示（注意，我们如何为用户1获得3个结果，即对于用户1的每个Growth记录一次）
User | age| Data |Growth------------------------ 1 |2 |43.5 |46.5 1 |2 |43.5 |49.5 1 |2 |43.5 |48.5 2 |3 |44.5 | 3 |4 |45.6 |
假设您仍然需要左联接；这是您在Linq中进行左联接的方法：
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 };如果要进行右连接，只需交换从中选择的表，如下所示：
var results = from growth in userGrowth join data in userData on growth.User equals data.User into joined from j in joined.DefaultIfEmpty() select new { UserData = j, UserGrowth = growth };该代码的重要部分是in语句，后跟DefaultIfEmpty。这告诉Linq如果另一个表中没有匹配的结果，我们希望具有默认值（即null）。
