vb.net - 直接给对象赋值

Question

例如，我有几个属性

Public Property FIRSTNAME As New SQLString("FirstName", 50)
Public Property FULLNAME As New SQLString("Name", 50)

SQLString 对象定义为:

Public Class SQLString
    Property SQL_Column As String
    Property Limit As Integer
    Property Value As String

    Public Sub New(SQLcolumn As String, limit_ As Integer)
        SQL_Column = SQLcolumn
        Limit = limit_
    End Sub

    Public ReadOnly Property SQL_value() As String
        Get
            Return "'" & clean(Value, Limit) & "'"
        End Get
    End Property
End Class

请注意，通过此方法，我的每个属性(例如 FIRSTNAME)都可以拥有多个子属性，这是必要的。

要访问它们，只需例如 FIRSTNAME.SQL_Column。

这是可行的，但是我希望也能够在 FIRSTNAME 属性本身上存储一个值(例如字符串数据类型)，这将使访问它的方式如下:

Dim MyFirstName As String = FIRSTNAME

而不是:

Dim MyFirstName As String = FIRSTNAME.Value

这就是我目前要做的事情。我能想到的唯一方法是默认将 SQLString 对象设置为字符串(或其他数据类型)，例如:

Public Class SQLString As String

显然上面的代码不起作用，但我想知道是否有等效的代码？

Answer 1

当未提供访问修饰符时，属性的默认访问修饰符(即:Public、Private 等)限制最严格。在 SQLString 类中，由于没有 Public类中属性前面的访问修饰符，它们本质上是 Private并且无法从类(class)外部访问。

向属性添加访问修饰符应该可以解决您看到的问题:

Public Property SQL_Column As String
Public Property Limit As Integer
Public Property Value As String

请告诉我投票失败的问题 - 这是上面建议的代码更改的有效 .NET fiddle ( https://dotnetfiddle.net/96o8qm )。

Imports System
Dim p as Person = new Person()
p.FIRSTNAME = new SQLString("Test", 1)
p.FIRSTNAME.Value = "Test Value"
Console.WriteLine("Person Value: {0}", p.FIRSTNAME.Value)

Public Class Person
    Public Property FIRSTNAME AS SQLString
End Class

Public Class SQLString
    Public Property SQL_Column As String
    Public Property Limit As Integer
    Public Property Value As String

    Public Sub New(SQLcolumn As String, limit_ As Integer)
        SQL_Column = SQLcolumn
        Limit = limit_
    End Sub

    Public ReadOnly Property SQL_value() As String
        Get
            Return ""
        End Get
    End Property

End Class

这会产生输出:

Person Value: Test Value