Question

I have a class in vb.net like

Public Class Customer
    Private _Name As String
    Public Overridable Property Name() As String
        Get
            Return _Name
        End Get
        Set(ByVal value As String)
            _Name = value
        End Set
    End Property
End Class

and a class deriving from it

Public Class ProxyCustomer
    Inherits Customer
    Private _name As String
    Public Overrides WriteOnly Property Name() As String
        Set(ByVal value As String)
            _name = value
        End Set
    End Property
End Class

which gives me following error
Public Overrides WriteOnly Property Name() As String’ cannot override ‘Public Overridable Property Name() As String’ because they differ by ‘ReadOnly’ or ‘WriteOnly’

but i have same construct in C#

public  class Customer 
{
    public virtual string FirstName { get; set; }     
}

public class CustomerProxy:Customer
{

   public override string FirstName
   {
       set
       {
           base.FirstName = value;
       }
   }

}

which works, so the first thing is , is this consistent because 2 languages are behaving in a very inconsistent way.

secondly, when i do a reflection to get a property, so for example

Dim propInfo  = GetType(Customer).GetProperty("Name")

the propINfo.canRead property is always false, shouldn’t this be true since base class implements the getter of the property ?

many thanks

Answer 1

I’ll deal with the 2nd part first. In your current vb.net code, the derived Name property replaces the original for the reflection lookup. So that reflection code only see the WriteOnly version of the property. Worse, you completely replace the backing store in your derived setter, so your getter is checking a completely different variable than the one you set.

As for the first question, when overriding properties in vb.net, you always need to override both the getter and the setter, even if you just replace it with an identical implementation:

The code should read like this:

Public Class ProxyCustomer
    Inherits Customer

    Public Overrides Property Name() As String
        Get
            Return MyBase.Name ''# Return the original parent property value
        End Get
        Set(ByVal value As String)
            MyBase.Name = value
        End Set
    End Property
End Class