Error -Reference to a non-shared member requires an object reference.

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Hi,
I get this error after I converted my window application into class library. Before that, it was successfully run. My window application form have a module. This error occur on the module in line Sensor1.Button_Send.Enabled = True and Sensor1.Button_Disconnect.Enabled = True.

Please help me or give some idea as i'm new in vb.

Form:

Public Class Sensor1

Public Sub Button_Send_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button_Send.Click

                If (ComPort.IsOpen = True) Then
            
                Application.DoEvents()

        Else
            MsgBox("COM port is not open.  Connect to a COM port and try again.")
        End If


    End Sub

 Public Sub Button_Disconnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button_Disconnect.Click

        Flag_Disconnect = True

        Application.DoEvents()

        ComPort.Close()
        Me.Button_Connect.Enabled = True
        Me.ComboBox1.Enabled = True
        Me.Button_Disconnect.Enabled = False
        Me.Button_Send.Enabled = False

        Me.ComboBox1.Items.Clear()
        
    End Sub
End Class

Module:

Imports System.IO
Imports System.Data

Module Module1

 Sub ConnectPort()
        
        Try
            ComPort = My.Computer.Ports.OpenSerialPort(PortNm)

            ComPort.BaudRate = 9600     
            ComPort.StopBits = 1 
            ComPort.Parity = 0      
            ComPort.DataBits = 8

            
            Sensor1.Button_Send.Enabled = True
            Sensor1.Button_Disconnect.Enabled = True

        Catch ex As Exception
            MsgBox("COM port: " & PortNm & " is used . Select an available port and try again.")
            Return
        End Try

    End Sub

End Module

Posted 16-Dec-13 16:15pm

nca8503

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Comments

Sergey Alexandrovich Kryukov 16-Dec-13 22:17pm

As I already mentioned, it would be interesting to know why did you change this part of code. What it was before? Is it about using some
members of a form or other control class outside of this class?
Oh... you did it wrong. "DoEvents"... For serial communication, you should rather use threading.
—SA

nca8503 16-Dec-13 22:25pm

i need to change this project to dll since i need to put this dll into another projectA.means I have another big projectA(window application form) that have button when user clicked, this dll project (exe program) will popup).I know i can call using shell the exe without convert to dll, how ever user want to have a control in this exe from projectA.

Sergey Alexandrovich Kryukov 16-Dec-13 22:37pm

I think I am asking your for the third time already, and you don't answer. Change to DLL cannot create this problem. I know why changing code to DLL and provided you with the detailed advice on this work. If your code compiled before porting it to DLL, it should compile after. If it does not compile, it means that you screw up something in the code.

How can you expect help if you ignore questions yourself?

—SA

Sergey Alexandrovich Kryukov 16-Dec-13 22:20pm

And please comment the line of code where the compilation error is shown.
What is Sensor1: class, structure, or instance of some type. Where is the declaration of ButtonSend?
—SA

nca8503 16-Dec-13 23:13pm

i'm not changing this code. the code is still same.i only convert by change type project to class library. and i also has said before.before i convert into class library it was successfully build and run. Sensor1 is class.i already put the code above (Public Class Sensor1). also write on question above which line the error occured. (This error occur on the module in line Sensor1.Button_Send.Enabled = True and Sensor1.Button_Disconnect.Enabled = True.)

Sergey Alexandrovich Kryukov 17-Dec-13 3:22am

It cannot be so. I insist: if you have some code which compile, and then change the application type to "Class Library", it will compile. It may not compile after some next step, but you never explained what it was. Did you follow my advice on migration steps I gave you to answer your previous question?
You can try a little experiment: get to your original project and makes the steps again, this time paying more attention. In fact, this is a pretty usual case when an inexperienced developer cannot reproduce her/his own steps, especially when one don't understand what she/he is doing. And apparently, you don't understand it — please see my answer.
—SA

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Member 10671113 · Answer 1 · 2014-03-14T09:23:00

"It cannot be so. I insist:"
"What to do? Quite certainly, not to develop UI applications, or communications, or anything advanced."

This is extremely rude and condescending, especially because the behavior he describes does happen.

Visual Basic projects have the concept of a default instance of a form:
http://stackoverflow.com/questions/4698538/there-is-a-default-instance-of-form-in-vb-net-but-not-in-c-why[^]

So if you convert the project from a Windows Form application to a class library you lose that behavior and depending on whether the existing code utilizes that default instance, you can have errors such as:

"Reference to a non-shared member requires an object reference."

I should also mention that you may receive other errors when converting to a class library such as this one:
"'End' statement cannot be used in class library projects"
http://msdn.microsoft.com/en-us/library/686w7tx3%28v=vs.90%29.aspx

So to state that when converting a project to a class library that it will compile exactly the same... is simply false.

Sergey Alexandrovich Kryukov · Answer 2 · 2013-12-16T16:33:00

Please see: http://msdn.microsoft.com/en-us/library/zc2b427x.aspx[^].

The type members can be shared or not. Those which are not shared are called instance members, because they a related to an instance of a type, not a type "at large" (in the pretty awkward phrasing used in the MSDN library referenced above). Different instances of the type with such members generally have different values (or referenced) of such members. Let's say you have a class MyClass with integer field or (read/write) property MyInstanceMember and Shared properly or field MySharedMember. Then

VB

MyClass.MyInstanceMember = 3 ' is invalid
' but
MyClass.MySharedMember = 4 ' is valid

What to do? Quite certainly, not to develop UI applications, or communications, or anything advanced. You are not ready yet. Instead, set it all aside and try to learn at least the basics of .NET, the language and OOP. Types versus instances, value types versus reference types, references, constants, variables and members, properties, delegates and events, all that stuff. And ultimately, OOP, up to virtual methods, late binding, polymorphism, interfaces, their declaration, implementation and use. It's the best to do it while doing exercises based on simple console-only application. If you jump right to real work, as you already did, you will only waste too much time and won't get real experience. Very seriously.

—SA

Sean Wood · Answer 3 · 2015-04-09T12:48:00

I concur that the first solution was rather unhelpful and came across condescending. A basic solution to the issue would be to pass an instanced reference to the parent class you're referring to in the module call and using that instance to enable or disable the buttons.

This might look something like this:

VB

Sub ConnectPort(ByRef c1 as Sensor1)

 Try
            ComPort = My.Computer.Ports.OpenSerialPort(PortNm)
 
            ComPort.BaudRate = 9600     
            ComPort.StopBits = 1 
            ComPort.Parity = 0      
            ComPort.DataBits = 8
 
            
            c1.Button_Send.Enabled = True
            c1.Button_Disconnect.Enabled = True
 
        Catch ex As Exception
            MsgBox("COM port: " & PortNm & " is used . Select an available port and try again.")
            Return
        End Try
 
    End Sub

If you were calling it from Sensor1 class itself you would do the call like so:

ConnectPort(me)

or if calling from outside the class library you would need to instantiate the Sensor1 class first

for instance:

VB

Dim S1 as Sensor1 = new Sensor1
ConnectPort(S1)

You might want to 'show' the s1 class object first as well if its a form.

VB

Dim S1 as Sensor1 = new Sensor1
S1.show()
ConnectPort(S1)

Hopefully thats a bit more of a helpful solution than 'quit programming you suck'

Error -Reference to a non-shared member requires an object reference.

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