的EntityFramework：檢查整數關係是空

Question

我得到一些樹，但 根的EF查詢：

SomeTree.Where(t => t.ParentID == null); 

或動態LINQ查詢：

SomeTree.Where("ParentID== null"); 

返回sql查詢：

SELECT 
CAST(NULL AS int) AS [C1], 
CAST(NULL AS int) AS [C2], 
CAST(NULL AS varchar(1)) AS [C3] 
FROM (SELECT 1 AS X) AS [SingleRowTable1] 
WHERE 1 = 0 

爲什麼它不返回根？

映射：

  HasKey(c => c.ID); 
      Property(c => c.ID).HasColumnName("ACTID").HasColumnType("int").HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity).IsRequired(); 
      Property(c => c.Title).HasColumnName("ACTName").HasColumnType("nvarchar").HasMaxLength(100).IsUnicode(true).IsVariableLength().IsRequired(); 
      Property(c => c.ParentID).HasColumnName("ACTActKindID").HasColumnType("int").IsOptional();    
      HasMany(c => c.Children).WithRequired(c => c.Parent).HasForeignKey(c => c.ParentID); 

Answer 1

WHERE 1 = 0 

看起來很糟糕，（IE這不會再回到）

我猜想，在數據庫中的心不是可空