如何将 Linq 动态查询结果转换为自定义类？

发布于 2024-08-27 02:38:22 字数 672 浏览 8 评论 0原文

通常，我会这样做：

var a = from   p in db.Products
        where  p.ProductType == "Tee Shirt"
        group  p by p.ProductColor into g
        select new Category { 
               PropertyType = g.Key,
               Count = g.Count() }

但我有这样的代码：

var a = Products
        .Where("ProductType == @0", "Tee Shirt")
        .GroupBy("ProductColor", "it")
        .Select("new ( Key, it.Count() as int )");

我可以改变什么语法来产生相同的结果，即，如何从第二个 Linq 语句中进行类别投影？

我都知道g 和 it 相同，代表整个表记录，~~我将整个记录拉入只是为了进行计数。我也需要解决这个问题。~~ 编辑：Marcelo Cantos 指出 Linq 足够聪明，不会提取不必要的数据。谢谢！

原文

Normally, I do this:

var a = from   p in db.Products
        where  p.ProductType == "Tee Shirt"
        group  p by p.ProductColor into g
        select new Category { 
               PropertyType = g.Key,
               Count = g.Count() }

But I have code like this:

var a = Products
        .Where("ProductType == @0", "Tee Shirt")
        .GroupBy("ProductColor", "it")
        .Select("new ( Key, it.Count() as int )");

What syntax could I alter to produce identical results, i.e., how do I do a projection of Category from the second Linq statement?

I know in both that g and it are the same and represent the entire table record, and that ~~I am pulling the entire record in just to do a count. I need to fix that too.~~ Edit: Marcelo Cantos pointed out that Linq is smart enough to not pull unnecessary data. Thanks!

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淡看悲欢离合 2024-09-03 02:38:22

为什么你必须这么做？由于在 GroupBy 调用后您仍然拥有所有信息，因此您可以轻松地执行此操作：

var a = Products
        .Where("ProductType == @0", "Tee Shirt")
        .GroupBy("ProductColor", "it")
        .Select(c => new Category { 
            PropertyType = g.Key, Count = g.Count() 
        });

Products 的类型仍应流经并可访问，并且常规分组/过滤不应改变流经扩展方法的类型。

Why would you have to do it at all? Since you still have all of the information after the GroupBy call, you can easily do this:

var a = Products
        .Where("ProductType == @0", "Tee Shirt")
        .GroupBy("ProductColor", "it")
        .Select(c => new Category { 
            PropertyType = g.Key, Count = g.Count() 
        });

The type of Products should still flow through and be accessible and the regular groupings/filtering shouldn't mutate the type that is flowing through the extension methods.

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