Question

我必须得到一些树的根，但是 EF查询：

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

或动态linq查询：

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

返回sql查询：

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

为什么它不会返回根源？

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

看起来很糟糕，（IE不会再回来了）

我猜你的数据库中的parentID列是不可为空的

EntityFramework：检查Integer关系是否为null

1 个答案: