Question

我正在尝试在派生类中添加共享成员并在基类中使用该值...

我有基地

class DBLayer
    public shared function GetDetail(byval UIN as integer)
    dim StrSql = string.format("select * from {0} where uin = {1}", tablename, uin)
    ....
    end function
end class

我的派生类

class User inherits dblayer
    public shared tabledname as string = "users"
end class

class item inherits dblayer
    public shared tabledname as string = "item"
end class

class category inherits dblayer
    public shared tabledname as string = "category"
end class

目前在我的基类中使用派生类的tablename变量时出错。

Answer 1

我要创建

Protected MustInherit Readonly Property TableName as string

在基类中。然后，每个子类都需要覆盖它并从属性中返回正确的名称。

因此，在其中一个子类中，它将是：

Protected OverRides Readonly Property TableName as string
   Get
       Return "users" ' or category or item etc
   End Get
End Property

Answer 2

Class User
    Inherits DBLayer
    Public Shared Shadows Function TableName() As String
        Return "users"
    End Function
    Public Overrides Function GetTableName() As String
        Return User.TableName
    End Function
End Class

MustInherit Class DBLayer
    MustOverride Function GetTableName() As String

    Public Function GetDetail(ByVal UIN As Integer)
        Return GetDetail(UIN, GetTableName)
    End Function

    Public Shared Function GetDetail(ByVal UIN As Integer, ByVal TableName As String)
        Dim StrSql As String = String.Format("select * from {0} where uin = {1}", TableName, UIN)
        Return StrSql
    End Function

End Class

Class DBLayer

    Private _tableName As String
    Public Property TableName() As String
        Get
            Return _tableName
        End Get
        Set(ByVal value As String)
            _tableName = value
        End Set
    End Property

    Public Sub New(ByVal tableName As String)
        _tableName = tableName
    End Sub
    Public Function GetDetail(ByVal UIN As Integer)
        Return GetDetail(UIN, Me.TableName)
    End Function

    Public Shared Function GetDetail(ByVal UIN As Integer, ByVal TableName As String)
        Dim StrSql As String = String.Format("select * from {0} where uin = {1}", TableName, UIN)
    End Function

End Class

如何在基类的共享方法中使用派生类共享变量

2 个答案: