Edit

BC30933: Latebound overload resolution cannot be applied to '<procedurename>' because the accessing instance is an interface type

  • Article

The compiler is attempting to resolve a reference to an overloaded property or procedure, but the reference fails because an argument is of type Object and the referring object has the data type of an interface. The Object argument forces the compiler to resolve the reference as late-bound.

In these circumstances, the compiler resolves the overload through the implementing class instead of through the underlying interface. If the class renames one of the overloaded versions, the compiler does not consider that version to be an overload because its name is different. This in turn causes the compiler to ignore the renamed version when it might have been the correct choice to resolve the reference.

Error ID: BC30933

To correct this error

  • Use CType to cast the argument from Object to the type specified by the signature of the overload you want to call.

    Note that it does not help to cast the referring object to the underlying interface. You must cast the argument to avoid this error.

Example

The following example shows a call to an overloaded Sub procedure that causes this error at compile time.

Module m1
    Interface i1
        Sub s1(ByVal p1 As Integer)
        Sub s1(ByVal p1 As Double)
    End Interface
    Class c1
        Implements i1
        Public Overloads Sub s1(ByVal p1 As Integer) Implements i1.s1
        End Sub
        Public Overloads Sub s2(ByVal p1 As Double) Implements i1.s1
        End Sub
    End Class
    Sub Main()
        Dim refer As i1 = New c1
        Dim o1 As Object = 3.1415
        ' The following reference is INVALID and causes a compiler error.
        refer.s1(o1)
    End Sub
End Module

In the preceding example, if the compiler allowed the call to s1 as written, the resolution would take place through the class c1 instead of the interface i1. This would mean that the compiler would not consider s2 because its name is different in c1, even though it is the correct choice as defined by i1.

You can correct the error by changing the call to either of the following lines of code:

refer.s1(CType(o1, Integer))
refer.s1(CType(o1, Double))

Each of the preceding lines of code explicitly casts the Object variable o1 to one of the parameter types defined for the overloads.

See also