Question

在实体框架中，我通常会执行以下操作：

modelBuilder.Entity(Of Model).HasKey(Function(item As Model) New With {item.PropertyA, item.PropertyB })

映射复合主键

我需要编写一个通用函数，如：

modelBuilder.Entity(Of TModelo).HasKey( MakeLambda({“PropertyA”, “PropertyB” })

Private Function MakeLambda(Of TModelo)(nameProperties As String()) As Expression(Of Func(Of TModelo, Object))
        Dim type = GetType(TModelo)

        Dim listProperties As New List(Of Expression)
        Dim parameter = Expression.Parameter(type, "item")
        For Each n As String In nameProperties
            Dim refProperty = type.GetProperty(n)
            listProperties.Add(Expression.MakeMemberAccess(parameter, refProperty))
        Next

        Dim arrayInit = Expression.NewArrayInit(GetType(Object), listProperties)

此时系统无法创建新表达

        Dim newExpression = Expression.Lambda(Of Func(Of TModelo, Object))(arrayInit)

        Return newExpression
End Function

可能有人有另一个解决这个问题的方法

Answer 1

这样做。 dynamic newExpression = Expression.Lambda＆gt;（arrayInit，parameter）;

但这对我来说还不行。我需要这样的东西......

HasKey(p => new { p.FAMILY, p.CACHE_FAMILY, p.CUSTOMER_CODE, p.CCC, p.OPERATION, p.EVAL_CODE, p.VDT_FLAG, p.TEST_PLATFORM, p.PCBA_VENDOR });

动态制作lambda表达式

1 个答案: