使用 LINQ 和 EF 4.1 填充字典具有相关实体数据的属性

发布于 2025-01-08 12:51:54 字数 532 浏览 0 评论 0原文

我有一个表Customers，它链接到另一个表Addresses。地址表的主键由 {CustomerID, LanguageID} 组成。

我想编写一个 LINQ 查询，在其中实例化一个类型并填充其

Dictionary地址 {get;set;}

属性与地址表中的地址。每种语言都将成为字典中的关键。

就像这样：

from c in customers
from a in c.Addresses
select new DataContainer
{
  ID = c.CustomerId,
  ...
  Addresses.Add(a.LanguageId, a),
  ...
};

我知道我确实无法在对象初始值设定项中执行 .Add() 调用，但是有没有办法使其工作？

注意：我当然可以像往常一样创建类型，然后返回并显式填充 Addresses 属性。

原文

I have a table Customers that is linked to another table Addresses.
The Addresses table has a Primary Key made up of {CustomerID, LanguageID}.

I would like to wrtie a LINQ query where I instantiate a type and populate its

Dictionary<string, Address> Addresses {get;set;}

property with the addresses in the Address table. Each Langauge is to become the key in the dictionary.

Like so:

from c in customers
from a in c.Addresses
select new DataContainer
{
  ID = c.CustomerId,
  ...
  Addresses.Add(a.LanguageId, a),
  ...
};

I know that I really can't do the .Add() call in an object initializer, but is there a way to make that work?

Note: I could of course create the type as usual and then go back in and populate the Addresses property explicitely.

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森林散布 2025-01-15 12:51:54

我不记得以下代码是否可以编译，但您可以尝试这样的事情：

from c in customers
from a in c.Addresses
select new DataContainer
{    
  Addresses = new Dictionary<string, Address> {{a.LanguageId, a}};
};

或者您可以尝试以下解决方案：
从LINQ 投影

I don't remember from memory if following code will compile, but you can try something like this:

from c in customers
from a in c.Addresses
select new DataContainer
{    
  Addresses = new Dictionary<string, Address> {{a.LanguageId, a}};
};

Or you can try following solution:
Instantiating a Dictionary from a LINQ projection

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债姬 2025-01-15 12:51:54

一种安全的方法是这样的：

如果 DataContainer 看起来像这样：

public class DataContainer
{
    public string ID { get; set; }
    public Address Address { get; set; }
}

您可以这样做：

from c in customers
from a in c.Addresses
select new DataContainer
{
  ID = c.CustomerId,
  Address = a
};
var dic = new Dictionary<string, Address>();

foreach (var n in query)
{
  dic.Add(ID,a);
}

或者简单地说，这样做：

var dic = query.ToDictionary<DataContainer, string, Address>(n => n.ID, n => n.a);

A safe way to do this is like so:

If DataContainer looks like this:

public class DataContainer
{
    public string ID { get; set; }
    public Address Address { get; set; }
}

You can do this:

from c in customers
from a in c.Addresses
select new DataContainer
{
  ID = c.CustomerId,
  Address = a
};
var dic = new Dictionary<string, Address>();

foreach (var n in query)
{
  dic.Add(ID,a);
}

Or for short do this:

var dic = query.ToDictionary<DataContainer, string, Address>(n => n.ID, n => n.a);

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机场等船 2025-01-15 12:51:54

回应约翰对亨克的评论。

我写了一个字典扩展

public static Dictionary<T, K> Build<T, K>(this Dictionary<T, K> dictionary, T key, K value)
{
       dictionary[key] = value;
       return dictionary;
}

现在你可以做这样的事情：

from c in customers
from a in c.Addresses
select new DataContainer
{    
  Addresses = new Dictionary<string, Address>()
                                              .Build(a.LanguageId, a)
};

对我来说它确实有效。 :)

In response to John's comment for henk.

I wrote a Dictionary extension

public static Dictionary<T, K> Build<T, K>(this Dictionary<T, K> dictionary, T key, K value)
{
       dictionary[key] = value;
       return dictionary;
}

Now you can do something like this:

from c in customers
from a in c.Addresses
select new DataContainer
{    
  Addresses = new Dictionary<string, Address>()
                                              .Build(a.LanguageId, a)
};

For me it does work. :)

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