Comment utiliser la classe dérivées des variables partagées dans les méthodes communes de classe de base

Question

Je suis en train d'ajouter des membres Partagés dans les classes dérivées et l'utilisation que les valeurs dans les classes de base ...

J'ai la base

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 

ma classe

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 

dérivé Actuellement, il y a une erreur en utilisant la variable tablename d'une classe dérivée dans ma classe de base.

Answer 1

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 

Answer 2

Je crée

Protected MustInherit Readonly Property TableName as string 

dans la classe de base. Et puis chacune des classes enfant devra le remplacer et retourner le nom correct de la propriété.

Ainsi, dans l'une des classes de l'enfant, il serait:

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