overload resolution failed

overload resolution failed

• Mats Hagberg

  Assuming you do have two methods ShowDistance (I could only see one in your code, but the error message states there are two), one that takes the IShared interface, and another that takes a parent class, then the error is expected - consider the following simplified code:
  

  Module Module1
  
    Sub Main()
      test(New c1)
    End Sub
  
    Interface i1
    End Interface
  
    Class c0
    End Class
  
    Class c1
      Inherits c0
      Implements i1
    End Class
  
    Sub test(ByVal arg As c0)
    End Sub
  
    Sub test(ByVal arg As i1)
    End Sub
  
  End Module
  

  In sub main, the compiler has two options to call - the thing is,
  the argument we're giving it can be converted to any of them, so
  the compiler can't make a decision - you can desambiguate the call 
  by casting the argument to the precise type the method you want to
  call takes: test(ctype(New c1,c0)) or test(ctype(New c1,i1)).

  
  
  

• voip

  Both lines show similar error messages.
  
  The first line:Private sub showdistance(object as parent): not most specific
  The second line: Private sub showdistance(object as interfaces.ishared):not most specific.
  
  Here are the rest of the classes:
  As you can see the authors are probably cramming too many concepts into one app, a sure recipe for making an error somewhere.
  
  dennist685
  
  Main App:
  
  Imports interfaces
  Public Class Poly
  Inherits Parent
  Implements IShared
  
  Public Overrides Function DistanceTo(ByVal x As Single, ByVal y As Single) As Single Implements IShared.CalculateDistance
  Return x + y
  End Function
  
  
  End Class
  
  Imports interfaces
  Public Class Encapsulation
  Inherits Parent
  Implements IShared
  Private mX As Single
  Private mY As Single
  Public Overrides Function DistanceTo(ByVal x As Single, ByVal y As Single) As Single Implements IShared.CalculateDistance
  Return Abs(x - mX) + Abs(y - mY)
  End Function
  Public Property CurrentX() As Single
  Get
  Return mX
  End Get
  Set(ByVal value As Single)
  mX = value
  End Set
  End Property
  Public Property CurrentY() As Single
  Get
  Return mY
  End Get
  Set(ByVal value As Single)
  mY = value
  End Set
  End Property
  
  End Class
  
  Public MustInherit Class Parent
  Public MustOverride Function DistanceTo(ByVal x As Single, _
  ByVal y As Single) As Single
  End Class
  
  Public MustInherit Class Contact
  Private mID As Guid = Guid.NewGuid
  Private mName As String
  
  Public Property ID() As Guid
  Get
  Return mID
  End Get
  Set(ByVal value As Guid)
  mID = value
  End Set
  End Property
  
  Public Property Name() As String
  Get
  Return mName
  End Get
  Set(ByVal value As String)
  mName = value
  End Set
  End Property
  
  End Class
  
  Public Class Customer
  Inherits Contact
  Private mPhone As String
  Public Property Phone() As String
  Get
  Return mPhone
  End Get
  Set(ByVal value As String)
  mPhone = value
  End Set
  End Property
  End Class
  
  Interfaces assembly(class library)
  
  Imports System.Drawing
  Public Interface IShared
  Function CalculateDistance(ByVal x As Single, ByVal y As Single) As Single
  End Interface
  
  Public Interface IPrintableObject
  Sub Print()
  Sub PrintPreview()
  Sub RenderPage(ByVal sender As Object, ByVal ev As System.Drawing.Printing.PrintPageEventArgs)
  End Interface
  
  Objects (class library)
  
  Imports Interfaces
  Public Class External
  Implements IShared
  Public Function DistanceTo(ByVal x As Single, ByVal y As Single) _
  As Single Implements IShared.CalculateDistance
  Return x * y
  End Function
  End Class
  
  
  
  
  
  
  
  

• Rafer_Smith

  You have these two calls:

  ShowDistance(New Poly)
  ShowDistance(New Encapsulation)

  Can you show us the Poly type and the Encapsulation type Also, knowing which line is giving the error will also help.

  Finally according to the error message, you have another ShowDistance method definition other than the one you showed us.

  
  
  

• ARTsev

  Without seeing all classes it's hard to figure out, but I have a feeling that the Parent class should implement the IShared interface...
  
  

• Larry Mason

  Thanks, Alex.
  
  This isn't the first error in the Wrox book.
  
  dennist685
  
  
• overload resolution failed