Change inheritance class at runtime - vb.net

Question

I have two class with code like this (it's just example)
class parent1
function f(param as integer) as integer
return param +2
end function
end class
'===============================
class parent2
function f(param as integer) as integer
return param *1
end function
end class
then i want to create a class inherits of one of boot based on situation at run time. maybe like this:
class child
sub new(s as string)
'it will inherits parent1
end sub
sub new(i as integer)
'it will inherits parent2
end sub
end class
Is it possible..?

Answer 1

.NET languages do not support multi inheritance and you cannot change it during runtime as pointed out in all comments you got.
Instead, nice "workaround" was created for this problem called Interface. Somebody call it a "hack" solution :)
For me your problem is a problem for dependency injection.
You want have child class which can change behavior during runtime.
Create abstraction of behavior, you want to change, as interface
Public Interface IBehavior
Function Calculate(value As Integer) As Integer
End Interface
Then create child class which takes behavior as constructor parameter
Public Class Child
Private ReadOnly _behavior As IBehavior
Public Sub New(behavior As IBehavior)
_behavior = behavior
End Sub
Public Sub Execute(int value)
Dim newValue As Integer = _behavior.Calculate(value)
' Do something else
End Sub
End Class
Create implementations of IBehavior you want to use during runtime
Public Class SumBehavior Implements IBehavior
Function Calculate(value As Integer) As Integer Implements IBehavior.Calculate
Return value + 2
End Function
End Class
Public Class MultiplyBehavior Implements IBehavior
Function Calculate(value As Integer) As Integer Implements IBehavior.Calculate
Return value * 2
End Function
End Class
Then during runtime you can change behavior of Child instance based on passed parameter
Dim sum As New SumBehavior()
Dim child As New Child(sum)
child.Execute(23)
Your problem is good example of "Open-Close Principle".
- Your Child class is closed for modifications -> Do something else staff in Execute method stays unmodified
- Your child class is open for modifications -> Behavior logic can be changed without touching Child class

Answer 2

Multiple inheritance is not possible in .Net. Now, to solve your problem
Try Dynamic Source Code Generation and Compilation. You can not do multiple inheritance but during runtime when its sure which type of class has to be inherited, dynamically create the class using CodeDom. Refer msdn link
This approach may or may not suit your need. Still if you have an scope to change the design, Use interfaces and dependency injection. (Since the function name is same in both the classes parent1 and parent2 you can take advantage of polymorphism).