级联IEquatable(Of T)

Question

我有几个实体需要分别创建(TEntity的)IEquatable。

我希望他们首先检查EntityId之间的等价性，然后如果两者都为零，则应该检查其他属性，例如相同的联系人姓名，相同的电话号码等。

这是怎么做的？

Answer 1

改编自MSDN IEquatable

Public Class Entity : Implements IEquatable(Of Entity)

    Public Overloads Function Equals(other As Entity) As Boolean _
                    Implements IEquatable(Of Entity).Equals
       If Me.Id = other.Id Then
           Return Me.ContactName = other.ContactName AndAlso Me.PhoneNumber = other.PhoneNumber
       Else
          Return False
       End If
    End Function

    Public Overrides Function Equals(obj As Object) As Boolean
       If obj Is Nothing Then Return MyBase.Equals(obj)

       If TypeOf obj Is Entity
          Return Equals(DirectCast(obj, Entity)) 
       Else
          Return False  
       End If
    End Function   

    Public Overrides Function GetHashCode() As Integer
       Return Me.Id.GetHashCode() Xor Me.ContactName.GetHashCode() Xor Me.PhoneNumber.GetHashCode()
    End Function

    Public Shared Operator = (entity1 As Entity, entity2 As Entity) As Boolean
       Return entity1.Equals(entity2)
    End Operator

   Public Shared Operator <> (entity1 As Entity, entity2 As Entity) As Boolean
      Return Not entity1.Equals(entity2)
   End Operator


End Class

备注：

GetHashCode的实现是幼稚的，如果您需要在生产环境中使用它，请阅读this SO问题的答案。