C＃Linq组合了两个DataTables的数据 [英] C# Linq combine data from two DataTables

问题描述

我有两个DataTable，其中一个字段连接两个表。我想加入这两个表，并将每个DataTable中的一些（或全部）列添加到一个新列中。我不认为使用LINQ会很困难，但我不知所措。



在SQL中它很容易，我只想写

I have two DataTables with one field connecting the two tables. I want to join the two tables and get some (or all) of the columns from each DataTable into a new one. I wouldn't think this would be difficult using LINQ but I am at a loss.

In SQL it is easy, I would just write

SELECT Table1.ID, Table1.Field1, Table2.Field2
FROM Table1 INNER JOIN Table2 ON Table1.ID = Table12.ID

什么是LINQ相当于上面的SQL代码??



我发现的所有例子都是这样的：

What is the LINQ equivalent to the SQL code above??

All the examples I find look something like this:

var query =
    from tbl1 in Table1.AsEnumerable()
    join tbl2 in Table2.AsEnumerable() on tbl1["ID"] equals tbl2["ID"] 
    select new  { ID = tbl1["ID"], Field1 = tbl1["Field1"], Field2 = tbl2"Field2"]};

DataTable newTable = new DataTable();
newTable.Columns.Add("ID",typeof(Guid));
newTable.Columns.Add("Field1", typeof(string));
newTable.Columns.Add("Field2",typeof(string));

foreach (var rowInfo in query)
{
   newTable.Rows.Add(rowInfo.ID, rowInfo.Field1, rowInfo.Field2);
}

这是一个很好的解决方案，如果他们真的是小桌子，但我'我正在使用具有10个左右列的表，这看起来非常混乱。是不是像SQL一样更直截了当？

That is a fine solution if they are really small tables but I'm working with tables that have 10 or so columns and that would look really messy. Is there not a more straight-forward way like in SQL?

推荐答案

创建数据表毫无意义。按照您的方式访问字段是没有意义的。你没有数据模型，所以你可以做tbl2.Id吗？为什么使用EF然后将结果填入数据表？



您可以使用反射来执行此操作。但你为什么要这样？如果您通常要创建连接，则应定义一个包含结果的类，然后选择一个列表。我可能更进一步，在一个过程中执行请求，让它返回一个强类型的类，并完成它。

Creating a data table at all makes no sense. Accessing fields the way you are, makes no sense. Do you not have a data model so you can just do tbl2.Id ? Why use EF then stuff the result in to a data table ?

You can probably use reflection to do this. But why would you ? If you're creating a join commonly, you should define a class to contain the results, and select a list of those. I'd probably go one step further and do the request in a procedure, and have it return a strongly typed class, and be done with it.

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