DLLs

[homebrew311]

Every time I make a DLL and try to use it, the host program always returns a "Object reference not set to the instance of an object" error. What am I doing wrong?

[PlausiblyDamp]

Could you show some code? It sounds like you are not setting a variable to a valid instance of an object...

[homebrew311]

Dll code

Public Class Class1
   Public Function Bob(ByVal int1 As Integer, ByVal int2 As Integer) As String
       Dim Ans As Integer
       Ans = int1 + int2
       Return Ans
   End Function
End Class

 

Button procedure

Private Sub btnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.Click
       Dim DLL As Dll_Test_Dll.Class1
       MsgBox(DLL.Bob(1, 2))
   End Sub

[PlausiblyDamp]

try the following...

Private Sub btnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.Click
       Dim DLL As New  Dll_Test_Dll.Class1    'change this line
       MsgBox(DLL.Bob(1, 2))
   End Sub

[bri189a]

you need the new keyword... at least in C# you would, probably the same for VB...

 

Dim DLL as New Dll_Test_Dll.Class1

[homebrew311]

Yeah I got it now. Thanks a lot guys.

[Heiko]

And while you're at it, you may want to clean up Class1.Bob as well, because the signature claims to return a sting, but in the code you return an integer. :)