LINQ編譯的查詢選擇和多列

Question

我有一個表：

ForObjectTypeID (short, PK) 
ForObjectID (int, PK) 
UserID (int, PK) 
Upvote (bool) 
ShadowBannedVote (bool) 

給定一個ObjectTypeID和ObjectID，我想返回Tuple<int, int, int>其中相應的值是：

• 總票數：其中ShadowBannedVote == false
• 總記錄數：的記錄總數，其中Upvote == true && ShadowBannedVote == false
• 總暗影禁止投票：記錄總數，其中ShadowBannedVote == true

它需要一個單一的編譯的查詢，而不是分成多個查詢。就我所知，我只是無法計算出如何在返回值中執行總和和計數。

public static readonly Func<DBContext, ObjectType, int, Tuple<int, int, int>> GetTotalVotes = CompiledQuery.Compile(
    (DBContext db, ObjectType forObjectType, int forObjectID) => 
    db.UserVotes.Where(c => c.ForObjectTypeID == (short)forObjectType && c.ForObjectID == forObjectID) 
    .Select(c=> new {c.Upvote, c.ShadowBannedVote}).Select(c=> new Tuple<int, int, in>(0, 0, 0))); 

Answer 1

會有興趣看看這是可能的，但一個解決辦法是：

public static readonly Func<DBContext, ObjectType, int, IEnumerable<Tuple<bool, bool>>> GetTotalVotes = CompiledQuery.Compile(
    (DBContext db, ObjectType forObjectType, int forObjectID) => 
    db.UserVotes.Where(c => c.ForObjectTypeID == (short)forObjectType && c.ForObjectID == forObjectID) 
    .Select(c=> new Tuple<bool, bool>(c.Upvote, c.ShadowBannedVote))); 

，然後只需在應用程序邏輯制定出號。

Answer 2

，你可以嘗試通過恆定的分組，總結和取結果，即像

public static readonly Func<DBContext, ObjectType, int, Tuple<int, int, int>> GetTotalVotes = CompiledQuery.Compile(
     (DBContext db, ObjectType forObjectType, int forObjectID) 
    => 
    db.UserVotes 
    .Where(c => c.ForObjectTypeID == (short)forObjectType 
      && c.ForObjectID == forObjectID) 
    .Select(c => new { c.Upvote, c.ShadowBannedVote }) 
    .GroupBy(c => 1) 
    .Select(c => new Tuple<int, int, int>(
     c.Count(r => !r.ShadowBannedVote), 
     c.Count(r => r.Upvote && !r.ShadowBannedVote), 
     c.Count(r => r.ShadowBannedVote) 
    )).Single());