将Linq To Entities查询结果绑定到datagridview [英] Binding Linq To Entities query results to a datagridview

问题描述

我刚刚开始使用Linq来处理Windows窗体应用程序中的实体，但是我不了解一种看起来如此简单的行为.

I just started playing with Linq to entities in a windows forms application and am not understanding one behavior that looks so simple though.

如果我在下面键入代码，则我的dataGridView中将获得ReadOnly记录

If i type code below, i get ReadOnly records in my dataGridView

Dim x = From n in Table1 _
        Select n.FirstName, n.LastName, N.Department
DataGridView1.DataSource = x 

但是，如果我输入以下代码，我的dataGridView中将获得可编辑的行

But if i type the following code, i get editable rows in my dataGridView

Dim x = From n in Table1 _
        Select n
DataGridView1.DataSource = x

因此，基本上，如果我指定要选择的列名称并将其数据绑定到我的DataGridView1，则行是只读的，但是如果我未指定列名称并将数据绑定到DataGridView，则这些行是可编辑的，并且我不明白为什么

So, basically if i specify the column names to select and databind to my DataGridView1, the rows are readonly but if i do not specify the column names and databind to the DataGridView, the rows are editable and i don't understand why.

推荐答案

有有关此的MSDN文章.

经过一番搜索并大量修改了我的答案，看来罪魁祸首必须是

After a little searching and lots of editing my answer, it seems like the culprit must be anonymous types. The documentation indicates that the non-key fields of anonymous types should be read-write, but you might be invoking some kind of exception to this rule. I would debug in and check the exact type of x in both cases.

此博客条目由某人提供. 在要生成密钥的任何情况下，LINQ查询表达式都会自动使用密钥字段(例如，分组依据，[...]").可能是使用Select方法创建的字段会自动关键属性.

There's another possible hint in this blog entry by someone. "The LINQ query expressions will automatically use Key fields in any situation where a key is going to be generated (for example, Group By), [...]" It might be that fields created by using the Select method are automatically Key properties.

另一个 Stackoverflow答案提示这-通过将Key放在其他类型的字段上，它们与Select方法调用的某些结果的类型匹配.

Another Stackoverflow answer hints at this - they match the type of some results from a Select method call by putting Key on the fields of the other type.

并且此文章(感谢Greg Stuntz)说出来. Geez.编写LINQ查询时，可以通过省略New With和{}来简化匿名类型定义，但是请注意，这会创建完全不可变的类型."

And this article (thanks, Greg Stuntz) comes right out and says it. Geez. "You can simplify the anonymous type definition when writing a LINQ query by omitting the New With and the { }'s, but be aware this creates fully immutable types."

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