c# - GroupBy ステートメントを動的に作成する

Question

ツリービューに表示されるデータを動的に再構築しようとしています。これにより、ユーザーは次のディメンションから最大 3 つを選択してデータをグループ化できます。

Organisation
Company
Site
Division
Department

たとえば、ユーザーが会社、サイト、部門の順にグループ化することを選択した場合、次のコードは必要なグループ化を実行します。

var entities = orgEntities
// Grouping Level 1
.GroupBy(o => new { o.CompanyID, o.CompanyName })
.Select(grp1 => new TreeViewItem
        {
        CompanyID = grp1.Key.CompanyID,
        DisplayName = grp1.Key.CompanyName,
        ItemTypeEnum = TreeViewItemType.Company,
        SubItems = grp1
               // Grouping Level 2
               .GroupBy(o => new { o.SiteID, o.SiteName })
               .Select(grp2 => new TreeViewItem
               {
               SiteID = grp2.Key.SiteID,
               DisplayName = grp2.Key.SiteName,
               ItemTypeEnum = TreeViewItemType.Site,
               SubItems = grp2
                  // Grouping Level 3
                  .GroupBy(o => new { o.Division })
                  .Select(grp3 => new TreeViewItem
                  {
                      DisplayName = grp3.Key.Division,
                      ItemTypeEnum = TreeViewItemType.Division,
                  }).ToList()
               }).ToList()
        })
.ToList();

これにより、次のような構造体が得られます。

+ Company A
  + Site A
    + Division 1
    + Division 2
  + Site B
    + Division 1
+ Company B
  + Site C
    + Division 2
+ Company C
  + Site D

ただし、これは多数の組み合わせの 1 つしか提供しません。

これを、ユーザーが選択した 3 つのディメンションに基づいて動的に同等の式を作成できるものに変換するにはどうすればよいでしょうか?

みんなありがとう。

score 4 · Accepted Answer

興味深い問題です。キーをグループ化するために単一のタイプを選択し、結果のために別のタイプを選択すると、求めているものを得ることが非常に可能になります。

public struct EntityGroupKey
{
  public int ID {get;set;}
  public string Name {get;set;}
}

public class EntityGrouper
{
  public Func<Entity, EntityGroupKey> KeySelector {get;set;}
  public Func<EntityGroupKey, TreeViewItem> ResultSelector {get;set;}
  public EntityGrouper NextGrouping {get;set;} //null indicates leaf level

  public List<TreeViewItem> GetItems(IEnumerable<Entity> source)
  {
    var query =
      from x in source
      group x by KeySelector(x) into g
      let subItems = NextGrouping == null ?
        new List<TreeViewItem>() :
        NextGrouping.GetItems(g)
      select new { Item = ResultSelector(g.Key), SubItems = subItems };

    List<TreeViewItem> result = new List<TreeViewItem>();
    foreach(var queryResult in query)
    {
          // wire up the subitems
      queryResult.Item.SubItems = queryResult.SubItems 
      result.Add(queryResult.Item);
    }
    return result;
  }

}

次のように使用します。

EntityGrouper companyGrouper = new EntityGrouper()
{
  KeySelector = o => new EntityGroupKey() {ID = o.CompanyID, Name = o.CompanyName},
  ResultSelector = key => new TreeViewItem
  {
    CompanyID = key.ID,
    DisplayName = key.Name,
    ItemTypeEnum = TreeViewItemType.Company
  }
}

EntityGrouper divisionGrouper = new EntityGrouper()
{
  KeySelector = o => new EntityGroupKey() {ID = 0, Name = o.Division},
  ResultSelector = key => new TreeViewItem
  {
    DisplayName = key.Name,
    ItemTypeEnum = TreeViewItemType.Division
  } 
}

companyGrouper.NextGrouping = divisionGrouper;

List<TreeViewItem> oneWay = companyGrouper.GetItems(source);

companyGrouper.NextGrouping = null;
divisionGrouper.NextGrouping = companyGrouper;

List<TreeViewItem> otherWay = divisionGrouper.GetItems(source);

score 0 · Accepted Answer

Another option is to use DynamicLinq. If this is straight LINQ (not through some DB context such as LINQ2SQL), then this can be done by composing your grouping/selector strings:

var entities = orgEntities
    .GroupBy("new(CompanyID, CompanyName)", "it", null) // DynamicLinq uses 'it' to reference the instance variable in lambdas.
    .Select(grp1 => new TreeViewItem
    {
        ...
        .GroupBy("new(SiteID, o.SiteName)", "it", null)
        // And so on...

You can probably abstract this into each of the criteria type. The only issue I see is the inner groupings might not be the easiest to compile together, but at least this can get you started in some direction. DynamicLinq allows you to build dynamic types, so it's certainly possible to abstract it even further. Ultimately, the biggest challenge is that based on what you're grouping by, the generated TreeViewItem contains different information. Good use case for dynamic LINQ, but the only problem I see is abstracting even further down the line (to the inner groupings).

Let us know what you come up with, definitely an interesting idea that I hadn't considered before.

c# - GroupBy ステートメントを動的に作成する

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