C# 如何将此Linq SQL编写为动态查询（使用字符串）？

根据需要跳到“特定问题”。一些背景：

场景：我有一组产品，其中有一个“向下钻取”过滤器（查询对象），填充了DDL。每个渐进式DDL选择将进一步限制产品列表以及DDL的剩余选项。例如，从工具中选择锤子会将产品尺寸限制为仅显示锤子尺寸

当前设置：我创建了一个查询对象，将其发送到存储库，并将每个选项提供给SQL“表值函数”，其中空值表示“获取所有产品”

我认为这是一个很好的努力，但远远不能接受DDD。我希望避免在SQL中进行任何“编程”，希望使用存储库完成所有工作。请就这一议题发表意见

具体问题：

.OrderBy("it.City") // "it" refers to the entire record
.GroupBy("City", "new(City)") // This produces a unique list of City
.Select("it.Count()") //This gives a list of counts... getting closer
.Select("key") // Selects a list of unique City
.Select("new (key, count() as string)") // +1 to me LOL.  key is a row of group
.GroupBy("new (City, Manufacturer)", "City") // New = list of fields to group by
.GroupBy("City", "new (Manufacturer, Size)") // Second parameter is a projection

Product
.Where("ProductType == @0", "Maps")
.GroupBy("new(City)", "new ( null as string)")// Projection not available later?
.Select("new (key.City, it.count() as string)")// GroupBy new makes key an object

Product
.Where("ProductType == @0", "Maps")
.GroupBy("new(City)", "new ( null as string)")// Projection not available later?
.Select("new (key.City, it as object)")// the it object is the result of GroupBy

var a = Product
        .Where("ProductType == @0", "Maps")
        .GroupBy("@0", "it", "City") // This fails to group Product at all
        .Select("new ( Key, it as Product )"); // "it" is property cast though

如何将此查询重写为一个查询？链接到类似的东西会非常棒，但是有一个动态的查询范围。我真的想把引号“”中的字段传递给这个方法，我想要一个选项列表，以及有多少产品具有该选项

from   p in db.Products
group  p by p.ProductSize into g
select new Category { 
       PropertyType = g.Key,
       Count = g.Count() }

每个DDL选项都有“选择（21）”，其中（21）是具有该属性的产品数量。选择一个选项后，所有其他剩余的DDL将使用剩余的选项和计数进行更新

编辑：其他注释：

.OrderBy("it.City") // "it" refers to the entire record
.GroupBy("City", "new(City)") // This produces a unique list of City
.Select("it.Count()") //This gives a list of counts... getting closer
.Select("key") // Selects a list of unique City
.Select("new (key, count() as string)") // +1 to me LOL.  key is a row of group
.GroupBy("new (City, Manufacturer)", "City") // New = list of fields to group by
.GroupBy("City", "new (Manufacturer, Size)") // Second parameter is a projection

Product
.Where("ProductType == @0", "Maps")
.GroupBy("new(City)", "new ( null as string)")// Projection not available later?
.Select("new (key.City, it.count() as string)")// GroupBy new makes key an object

Product
.Where("ProductType == @0", "Maps")
.GroupBy("new(City)", "new ( null as string)")// Projection not available later?
.Select("new (key.City, it as object)")// the it object is the result of GroupBy

var a = Product
        .Where("ProductType == @0", "Maps")
        .GroupBy("@0", "it", "City") // This fails to group Product at all
        .Select("new ( Key, it as Product )"); // "it" is property cast though

到目前为止，我所学到的是非常棒的，但仍然在寻找答案。我想最终，像这样完全随机的研究会占上风。哈哈

编辑：

.OrderBy("it.City") // "it" refers to the entire record
.GroupBy("City", "new(City)") // This produces a unique list of City
.Select("it.Count()") //This gives a list of counts... getting closer
.Select("key") // Selects a list of unique City
.Select("new (key, count() as string)") // +1 to me LOL.  key is a row of group
.GroupBy("new (City, Manufacturer)", "City") // New = list of fields to group by
.GroupBy("City", "new (Manufacturer, Size)") // Second parameter is a projection

Product
.Where("ProductType == @0", "Maps")
.GroupBy("new(City)", "new ( null as string)")// Projection not available later?
.Select("new (key.City, it.count() as string)")// GroupBy new makes key an object

Product
.Where("ProductType == @0", "Maps")
.GroupBy("new(City)", "new ( null as string)")// Projection not available later?
.Select("new (key.City, it as object)")// the it object is the result of GroupBy

var a = Product
        .Where("ProductType == @0", "Maps")
        .GroupBy("@0", "it", "City") // This fails to group Product at all
        .Select("new ( Key, it as Product )"); // "it" is property cast though

Jon Skeet有一个奇妙的想法：将我需要的内容转换为

I分组

。多亏了乔恩·斯基特！强制转换对象后，您可以枚举集合并将结果输入到单独的列表中。

如果您看一下，作者将讨论如何使用动态数据创建级联过滤器。听起来您并不是在使用动态数据，但他确实有一个很好的表达式生成器，可能会对您有所帮助。请参见BuildQueryBody，然后是Iqueryable上扩展方法的以下部分

由于您没有使用动态数据，您将需要处理无法访问“MetaForeignKeyColumn”对象的问题，但我怀疑他的方法可能有助于解决您的问题

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我希望这有帮助

我不知道如何使用查询语法（如上所述）实现这一点，但是使用方法语法，我们可以使用一个表达式new{ Key=group.Key， Count=group.Count（） }); foreach（结果中的var结果） WriteLine（“{0}:{1}”，result.Key，result.Count）； } Console.ReadKey（）； } } }

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您需要完整的动态查询吗？你的过滤条件（Where子句）不是唯一动态的方面吗？我相信我需要一个完整的DQ。在不为每个要筛选的字段复制此代码的情况下，我需要将GroupBy字段指定为字符串。只有在返回“it”时才能转换为IGroupping。当您使用.Select（“new（Key，it as Product，count（）as count）”）时，如何转换此属性？？？？