How to hold a reference to a field in VB? - vb.net

Question

In VB, I have a class that does some standard validations. What I'd LIKE to do is to declare some variables, then create instances of a validator class that include pointers to the variables, and then at some later time execute the validators to test the values in the fields that are pointed to.
Something like this:
public class MyData
public property foo as string
public property bar as string
dim vfoo as validator
dim vbar as validator
public sub new()
vfoo=new validator(&foo) ' i.e. & operator like in C
vbar=new validator(&bar)
end sub
public sub validate()
vfoo.validate
vbar.validate
end sub
end class
public class validator
dim _field as string* ' i.e. * like in C
public sub new(field as string*)
_field=field
end sub
public sub validate
if string.isnullorempty(_field) then
throw SomeException
else if not SomeOtherTest(_field) then
throw SomeOtherException
end sub
The catch is that, to the best of my knowledge, there is nothing like C pointers in VB. Is there any reasonably easy way to do this?
At present I am passing in the field values at the time I call the validate() function, but this is not ideal because I would like to be able to create a List of validators specific to a given caller, and then loop through the List. But at the time I loop, how would I know which value from MyClass to pass in, unless I had a giant select statement keying off some "field code"? (And of course in real life, there are not just two fields like in this example, there are quite a few.)
Am I just having a brain freeze and there's an easy way to do this? Or can this not be done in VB because there are no such thing as pointers?

Answer 1

Like Java, VB doesn't make direct use of pointers (it compensates where it can with library/framework calls). In the context of a garbage-collected language, I can't imagine that this style of validation would work out well.
But for fun, maybe a lambda-based solution could suit?:
Public Class MyData
Public Property foo As String
Public Property bar As String
Dim vfoo As validator
Dim vbar As validator
Public Sub New()
vfoo = New validator(Function() foo)
vbar = New validator(Function() bar)
End Sub
Public Sub validate()
vfoo.validate()
vbar.validate()
End Sub
End Class
Public Class validator
ReadOnly _fieldFunc As Func(Of String)
Public Sub New(fieldFunc As Func(Of String))
_fieldFunc = fieldFunc
End Sub
Public Sub validate()
Dim _field = _fieldFunc()
If String.IsNullOrEmpty(_field) Then
Throw New Exception("NullOrEmpty")
ElseIf Not SomeOtherTest(_field) Then
Throw New Exception("SomeOtherTest")
End If
End Sub
Public Function SomeOtherTest(f As String) As Boolean
Return True
End Function
End Class