我需要一个帮助,
我有两个dataTable称为A和B,我需要所有行从A和匹配行的B
例如：
A: B: User | age| Data ID | age|Growth 1 |2 |43.5 1 |2 |46.5 2 |3 |44.5 1 |5 |49.5 3 |4 |45.6 1 |6 |48.5
我需要Out Put：
User | age| Data |Growth ------------------------ 1 |2 |43.5 |46.5 2 |3 |44.5 | 3 |4 |45.6 |
解决方法
您提供的示例数据和输出未显示左连接.如果是左连接,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,即用户1拥有的每个成长记录一次)：
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 |
假设你还需要左连接;以下是您在Linq中进行左加盟的方式：
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
};
如果你想做一个正确的连接,只需将你所选择的表互换,就像这样：
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
};
代码的重要部分是into语句,后跟DefaultIfEmpty.这告诉Linq,如果在另一个表中没有匹配的结果,我们希望具有默认值(即为null).
