CODEWITHSUNDEEP
vb.nettype-conversion
Arsalan
Arsalan

Reputation: 744

Widening conversion operator VB.NET

I have a class named Foo with properties like this: 

Public Class Foo(Of T)
    public Property Value as T
    public Property Bar as Boolean  
End Class

I have a type conversion function overload :

 Public Shared Narrowing Operator CType(ins As [Foo](Of T)) As T
     Return ins.Value
 End Operator
 Public Shared Widening Operator CType(prop As T) As [Foo](Of T)
     Return New Foo(Of T) With {.Value = prop}
 End Operator

I using my class like this:

private Sub someSub()
   Dim f as new Foo(of String)
   f.Bar = True
   f = "This is The Text"
   // when doing this I lose the `Bar` beacuase of `Return New Foo(Of T) With {.Value = rightSide}` on `Widening` overload
End Sub

is there any way to keep other properties of the class?

Upvotes: 1

Views: 694

Answers (1)

jmcilhinney
jmcilhinney

Reputation: 54417

How could there be? When you assign to f you are creating a new Foo(Of T) object that knows nothing about the Bar property of the object already assigned to that variable. You'd have to set the Bar property of the new object inside the operator but it knows nothing about the variable you're assigning the result to so it can't get that value either. To keep that property value you would have to first get it and you have no way to get it other than the obvious manual retrieval beforehand and manual resetting afterwards.

Upvotes: 1

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