Code can not runnin after called from ribbon button

[SandmanINV]

Hi everybody, 

I am trying to bring my current addin to ribbon menu. 

From Addinstandardserver i can create my ribbon with buttons. 

I this file, I call my form (which have buttons, textbox....which can run Ok in exe file). 

        Dim oform1 As New Form1(_InvApplication)
        Private Sub btn_duoiphoi1(Context As NameValueMap) Handles btn_duoiphoi.OnExecute
            oform1.ShowDialog()
        End Sub

After form showed. I click can not excecute any button, it have error like this image

What should I do ?

Thank you,

[SandmanINV · Accepted solution]

I solved problem. Thanks for reading.