如何将包含联接的 linq-to-entities 查询绑定到可写 datagridview？

发布于 2024-10-11 02:09:33 字数 1453 浏览 3 评论 0原文

这个问题，虽然类似至其他，似乎不是重复的。如果是，请澄清，我很乐意合并。

我想使用包含联接的 linq-to-entities 查询绑定到可写 DataGridView。模型如下：

alt text

非规范化的 DataGridView 应该像这样绑定：

alt text

以下代码绑定但会生成只读 DataGridView，因为 linq-to-entities 查询返回匿名类型 (查看这篇文章）。我陷入了僵局，因为我认为我需要匿名类型来进行非规范化。

var query = from t in iDictionaryContext.DisplayTexts
        from l in iDictionaryContext.Languages
        where
            t.LanguageID == l.LanguageID
        select new
         {
             Key = t.DisplayKey,
             Text = t.DisplayText1,
             Language = l.LanguageName
         };

我还尝试了此处建议的解决方案，但是它似乎适用于 linq-to-sql 但不适用于 linq-to-entities。将 bindingsource.datasource 设置为 linq-toentities 查询时，会引发异常，显示“LINQ to Entities 仅支持无参数构造函数和初始化程序”。

谢谢你的建议，

蒂姆

原文

This question, although similar to others, doesn't seem to be a duplicate. If it is, please clarify and I will be happy to merge.

I want to bind to a writable DataGridView using a linq-to-entities query containing a join. The model is as follows:

alt text

The denormalized DataGridView should be bound like so:

alt text

The following code binds but results in a readonly DataGridView because the linq-to-entities query returns an anonymous type (see this post). I'm at an impasse because I think I need the anonymous type to do the denormalization.

var query = from t in iDictionaryContext.DisplayTexts
        from l in iDictionaryContext.Languages
        where
            t.LanguageID == l.LanguageID
        select new
         {
             Key = t.DisplayKey,
             Text = t.DisplayText1,
             Language = l.LanguageName
         };

I also tried the solution suggested here but it seems to apply to linq-to-sql but not to linq-to-entities. When setting the bindingsource.datasource to the linq-to-entities query, an exception is thrown reading "Only parameterless constructors and initializers are supported in LINQ to Entities."

Thank you for your advice,

Tim

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无人问我粥可暖 2024-10-18 02:09:33

只需像这样定义演示类型即可。您不必在构造函数中传递对象：

public class LanguageDisplayTextPresentation 
{
    public int Key { get; set; }
    public string Text { get; set; }
    public string Language { get; set; }
}

然后

var query = from t in iDictionaryContext.DisplayTexts
    from l in iDictionaryContext.Languages
    where
        t.LanguageID == l.LanguageID
    select new LanguageDisplayTextPresentation 
    {
        Key = t.DisplayKey,
        Text = t.DisplayText1,
        Language = l.LanguageName
    };

Just define presentation type like that. You don't have to pass objects in constructor:

public class LanguageDisplayTextPresentation 
{
    public int Key { get; set; }
    public string Text { get; set; }
    public string Language { get; set; }
}

and then

var query = from t in iDictionaryContext.DisplayTexts
    from l in iDictionaryContext.Languages
    where
        t.LanguageID == l.LanguageID
    select new LanguageDisplayTextPresentation 
    {
        Key = t.DisplayKey,
        Text = t.DisplayText1,
        Language = l.LanguageName
    };

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