Generics - What Does .Net For Each Loop Look At To Infer The Type

In the following code,

For Each item in MyCollection
...
Next

What does the compiler use to determine the type of item?For example let say I have this class, which is inheriting a non generic collection,

Public Class BaseDataObjectGenericCollection(Of T)
Inherits BaseDataObjectCollection
End Class

A for each loop still infers the Item type as Object. How would I have to modify the above class to make the type inference work?

Edit: Per Beatles1692's answer, Implementing IEnumerator(Of T) kinda works. The base class already has a GetEnumerator function, inherited from CollectionBase, so I my implementation looked like this,

Public Function GetEnumerator1() As System.Collections.Generic.IEnumerator(Of T) Implements System.Collections.Generic.IEnumerable(Of T).GetEnumerator
Return MyBase.Cast(Of T)().GetEnumerator
End Function

However, the for loop still infers the type as object. But, if I change the interface implementation to this,

Public Shadows Function GetEnumerator() As System.Collections.Generic.IEnumerator(Of T) Implements System.Collections.Generic.IEnumerable(Of T).GetEnumerator
Return MyBase.Cast(Of T)().GetEnumerator
End Function

That works, the for loop gets the type inference correct. So I guess the question is now, does For Each just look for a function called GetEnumerator ?