动态LINQ GroupBy多列

Question

我需要将以下LINQ查询转换为动态LINQ,它根据用户输入接受多个分组列.基本上我有一堆应用分组的下拉列表,我不想枚举每个分组组合.如果动态LINQ失败,我可能必须手动构建SQL查询,没有人想要它.

var grouping = ( from entry in ObjectContext.OmniturePageModules
    where entry.StartOfWeek >= startDate && entry.StartOfWeek <= endDate &&
        ( section == "Total" || section == "All" || entry.Section == section ) &&
        ( page == "Total" || page == "All" || entry.Page == page ) &&
        ( module == "Total" || module == "All" || entry.Module == module ) 
    group entry by new
    {
        entry.Page, // I want to be able to tell this anonymous type
        entry.Module, // which columns to group by
        entry.StartOfWeek // at runtime
    }
    into entryGroup
    select new
    {
        SeriesName = section + ":" + entryGroup.Key.Page + ":" + entryGroup.Key.Module,
        Week = entryGroup.Key.StartOfWeek,
        Clicks = entryGroup.Sum( p => p.Clicks )
    } );

我不知道如何做到这一点,因为动态LINQ在"你好世界"之外完全没有文档记录!选择/ where/orderby案例.我只是无法弄清楚语法.

就像是:(？)

var grouping = ObjectContext.OmniturePageModules.Where(entry => entry.StartOfWeek >= startDate && entry.StartOfWeek <= endDate &&
                                           ( section == "Total" || section == "All" || entry.Section == section ) &&
                                           ( page == "Total" || page == "All" || entry.Page == page ) &&
                                           ( module == "Total" || module == "All" || entry.Module == module ))
                                           .GroupBy("new (StartOfWeek,Page,Module)", "it")
                                           .Select("new (Sum(Clicks) as Clicks, SeriesName = section + key.Page + Key.Module, Week = it.Key.StartOfWeek)");

我在System.Linq.Dynamic中使用DynamicQueryable类.请参阅:http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx

后续行动:Enigmativity的解决方案主要起作用.由于某种原因,它不希望按日期时间"StartOfWeek"列进行分组 - 解决方法只是进行二级分组:

var entries = ( from entry in ObjectContext.OmniturePageModules
                            where entry.StartOfWeek >= startDate
                                && entry.StartOfWeek <= endDate
                                && ( section == "Total" || section == "All" || entry.Section == section )
                                && ( page == "Total" || page == "All" || entry.Page == page )
                                && ( module == "Total" || module == "All" || entry.Module == module )
                            select entry ).ToArray(); // Force query execution

            var grouping = from entry in entries
                            let grouper = new EntryGrouper( entry, section, page, module )
                            group entry by grouper into entryGroup
                            select new
                            {
                                entryGroup.Key.SeriesName,
                                entryGroup.Key.Date, 
                                Clicks = entryGroup.Sum( p => p.Clicks ),
                            };

            var grouping2 = (from groups in grouping
                            group groups by new {groups.SeriesName, groups.Date } into entryGroup
                            select new
                            {
                               entryGroup.Key.SeriesName,
                               entryGroup.Key.Date,
                               Clicks = entryGroup.Sum( p => p.Clicks ),
                            } );

但这似乎严重降低了性能...... = /

Answer 1

这是动态LINQ - 当然你在运行时构建GroupBy和Select字符串:

var double_grouping = ( ObjectContext.OmniturePageModules.Where( entry => entry.StartOfWeek >= startDate
                     && entry.StartOfWeek <= endDate
                     && ( section == "Total" || section == "All" || entry.Section == section )
                     && ( page == "Total" || page == "All" || entry.Page == page )
                     && ( module == "Total" || module == "All" || entry.Module == module ) )
                     .GroupBy( "new ( it.Section, it.Page, it.StartOfWeek )", "it" ) )
                     .Select( "new ( Sum(Clicks) as Clicks, Key.Section as SeriesSection, Key.Page as SeriesPage, Key.StartOfWeek as Week )" );

这是正常的LINQ方式,直到同事指出它才逃过我 - 这基本上是没有石斑鱼类的Enigmativity的解决方案:

var grouping = ( from entry in ObjectContext.OmniturePageModules
    where entry.StartOfWeek >= startDate && entry.StartOfWeek <= endDate &&
        ( section == "Total" || section == "All" || entry.Section == section ) &&
        ( page == "Total" || page == "All" || entry.Page == page ) &&
        ( module == "Total" || module == "All" || entry.Module == module )
    group entry by new
    {
        Section = section == "All" ? entry.Section : section,
        Page = page == "All" ? entry.Page : page,
        Module = module == "All" ? entry.Module : module,
        entry.StartOfWeek
    }
        into entryGroup
        select new
        {
            SeriesName =
            entryGroup.Key.Section + ":" + entryGroup.Key.Page + ":" + entryGroup.Key.Module,
            Week = entryGroup.Key.StartOfWeek,
            Clicks = entryGroup.Sum( p => p.Clicks )
        } );

Answer 2

如果您明确想要使用 LINQ 动态查询库，那么我的答案不会是您想要的，但如果您想要您想要的行为并且您很乐意使用常规 LINQ，那么我想我可以提供帮助。

本质上，我创建了一个EntryGrouper类，用于处理按下拉列表中所选值进行分组的逻辑，并且我假设变量section, page&module保存这些值。我还假设这ObjectContext.OmniturePageModules是一个类型的可枚举Entry。

所以你的 LINQ 查询现在变成这两个：

var entries = (from entry in ObjectContext.OmniturePageModules
               where entry.StartOfWeek >= startDate
                   && entry.StartOfWeek <= endDate
                   && (section == "Total" || section == "All" || entry.Section == section)
                   && (page == "Total" || page == "All" || entry.Page == page)
                   && (module == "Total" || module == "All" || entry.Module == module)
               select entry).ToArray(); // Force query execution

var grouping = from entry in entries
               let grouper = new EntryGrouper(entry, section, page, module)
               group entry by grouper into entryGroup
               select new
               {
                   SeriesName = entryGroup.Key.SeriesName,
                   Week = entryGroup.Key.StartOfWeek,
                   Clicks = entryGroup.Sum(p => p.Clicks),
               };

第一个查询用于强制对数据库执行简单的选择查询，并仅返回要分组的记录。通常group by查询会多次调用数据库，因此以这种方式查询通常要快得多。

EntryGrouper第二个查询通过创建类的实例作为分组键来对第一个查询的结果进行分组。

我SeriesName在类中包含了一个属性EntryGrouper，以便所有分组逻辑都整齐地定义在一个位置。

现在，该类EntryGrouper非常大，因为为了允许分组工作，它需要具有StartOfWeek、Section、Page&的属性，并包含&方法Module的重载，并实现接口。EqualsGetHashCodeIEquatable<Entry>

这里是：

public class EntryGrouper : IEquatable<Entry>
{
    private Entry _entry;
    private string _section;
    private string _page;
    private string _module;

    public EntryGrouper(Entry entry, string section, string page, string module)
    {
        _entry = entry;
        _section = section;
        _page = page;
        _module = module;
    }

    public string SeriesName
    {
        get
        {
            return String.Format("{0}:{1}:{2}", this.Section, this.Page, this.Module);
        }
    }

    public DateTime StartOfWeek
    {
        get
        {
            return _entry.StartOfWeek;
        }
    }

    public string Section
    {
        get
        {
            if (_section == "Total" || _section == "All")
                return _section;
            return _entry.Section;
        }
    }

    public string Page
    {
        get
        {
            if (_page == "Total" || _page == "All")
                return _page;
            return _entry.Page;
        }
    }

    public string Module
    {
        get
        {
            if (_module == "Total" || _module == "All")
                return _module;
            return _entry.Module;
        }
    }

    public override bool Equals(object other)
    {
        if (other is Entry)
            return this.Equals((Entry)other);
        return false;
    }

    public bool Equals(Entry other)
    {
        if (other == null)
            return false;
        if (!EqualityComparer<DateTime>.Default.Equals(this.StartOfWeek, other.StartOfWeek))
            return false;
        if (!EqualityComparer<string>.Default.Equals(this.Section, other.Section))
            return false;
        if (!EqualityComparer<string>.Default.Equals(this.Page, other.Page))
            return false;
        if (!EqualityComparer<string>.Default.Equals(this.Module, other.Module))
            return false;
        return true;
    }

    public override int GetHashCode()
    {
        var hash = 0;
        hash ^= EqualityComparer<DateTime>.Default.GetHashCode(this.StartOfWeek);
        hash ^= EqualityComparer<string>.Default.GetHashCode(this.Section);
        hash ^= EqualityComparer<string>.Default.GetHashCode(this.Page);
        hash ^= EqualityComparer<string>.Default.GetHashCode(this.Module);
        return hash;
    }

    public override string ToString()
    {
        var template = "{{ StartOfWeek = {0}, Section = {1}, Page = {2}, Module = {3} }}";
        return String.Format(template, this.StartOfWeek, this.Section, this.Page, this.Module);
    }
}

这个类的分组逻辑看起来就像这样：

if (_page == "Total" || _page == "All")
    return _page;
return _entry.Page;

如果我误解了下拉值如何打开和关闭分组，那么您只需要更改这些方法，但此代码的关键在于，当分组打开时，它应该根据条目中的值返回一个组值，并且否则它应该为所有条目返回一个公共值。如果该值对于所有条目都是通用的，那么它在逻辑上仅创建一个组，这与根本不分组相同。

如果您有更多要分组的下拉菜单，那么您需要向该类添加更多属性EntryGrouper。不要忘记将这些新属性也添加到Equals&GetHashCode方法中。

因此，这个逻辑代表了您想要的动态分组。如果我有帮助或者您需要更多详细信息，请告诉我。

享受！