Problems with data exchange beatween forms

[Fact]

Hello all,

I am trying to make an application, that gets data from OPC server to form1 and displays some pieces in form2. The app works that way: on start - form1 starts. Form2 must be started manually after form form1 is statrted (i mad a buttton for that). If some values in OPC server changes i need to see some of them in form2. Here is a sub which shows how do i get data from OPC server.

Public mObject As List (Of Object)
    Overridable Sub OnDataChange( _
    ByVal dwTransid As Integer, _
    ByVal hGroup As Integer, _
    ByVal hrMasterquality As Integer, _
    ByVal hrMastererror As Integer, _
    ByVal dwCount As Integer, _
    ByVal phClientItems() As Integer, _
    ByVal pvValues() As Object, _
    ByVal pwQualities() As Short, _
    ByVal pftTimeStamps() As OpcRcw.Da.FILETIME, _
    ByVal pErrors() As Integer) Implements IOPCDataCallback.OnDataChange

        Dim i As Integer = 0
        Dim j As Integer = 1
        Dim k As Integer = 0

        If dwCount > 0 Then

            mObject = New List(Of Object)
            For i = 0 To jk - 1
                For j = 1 To jk
                    If phClientItems(i) = j Then
                        mObject.Add(pvValues(k))
                        k += 1
                    End If
                Next j
            Next i
        End If
        dwCount = 0
    End Sub

I have tried to write line before sub end

Dim c As Integer
For c=0 To mObject.Count - 1
Form2.mObject.Add(Object(c))
Next c

but nothing happened when i opened form2, nor on change of data in OPC server (i wrote the code that on form2 load all values are shown in msgbox, message box did not show up).

dwCounts - how many values were changed in PLC.
phClientItems - variable index.
pvValues - variable value.

All the ideas are wellcome.

Thank you in advance.

[Shaggy Hiker]

That may do things you completely do not want, and there are several possible issues.

1) Since you say Form2.whatever, that strongly suggests that you are using the default instance there. I thoroughly detest the default instance, as it causes more confusion than any possible benefit. I'm not quite sure what behavior you saw, but what the default instances may trip you up. Are you displaying the default instance of Form2, or are you displaying a different instance.

2) You are passing around lots of reference types, such as when you add the object to the list from the array of object argument. That will copy the address of the item at the array index, but not the item itself. This could be correct, depending on how you are creating that array of object, but is that what you want to do? You then copy that address across to Form2. In that case, it probably will work, as the List is re-created each time the sub is run.

[Fact]

Well, i am trying to do so that data from OPC server are populated in datagrid on form2. I do not have any problems with displaying data in datagrid on form1 :

Public mObject As List (Of Object)
    Overridable Sub OnDataChange( _
    ByVal dwTransid As Integer, _
    ByVal hGroup As Integer, _
    ByVal hrMasterquality As Integer, _
    ByVal hrMastererror As Integer, _
    ByVal dwCount As Integer, _
    ByVal phClientItems() As Integer, _
    ByVal pvValues() As Object, _
    ByVal pwQualities() As Short, _
    ByVal pftTimeStamps() As OpcRcw.Da.FILETIME, _
    ByVal pErrors() As Integer) Implements IOPCDataCallback.OnDataChange

        Dim i As Integer = 0
        Dim j As Integer = 1
        Dim k As Integer = 0

        If dwCount > 0 Then

            mObject = New List(Of Object)
            For i = 0 To jk - 1
                For j = 1 To jk
                    If phClientItems(i) = j Then
                        DataGridView1.Rows(j-1).Cells(1).Value=Convert.ToString(pvValues(k))
                        mObject.Add(pvValues(k))
                        k += 1
                    End If
                Next j
            Next i
        End If
        dwCount = 0

But i need to do so that those values are displayed in form2 datagrid. I was thinking to make a public sub in form2, something like:

Public Sub xxx()
Dim a As Integer
For a=0 to jk
DataGridView1.Rows(a).Cells(1).Value=Convert.TosString(mObject(i))
Next a
End Sub

But then what? Or maybe the way i am trying to do it is not correct, i have no ideas.

[Fact]

Well, just to be sure, that data comes i put a button on form2 and wrote code in its click event

Dim i As Integer

For i=0 To Form1.mObject.Count - 1
DataGridView1.Rows(i).Cells(1).Value=Form1.mObject(i)
Next i

and datagrid in form2 was filled with values from OPC server. How to make this code working without clicking of button? I can do it on form2 load, but it will work only on form2 loading.

[chris128]

You dont want it to happen when the user clicks a button and you dont want it to happen when the form loads, so when do you want it to happen?

[Shaggy Hiker]

Is that OnDataChange running in a background thread?

[Fact]

@chris128, this is a real time monitoring, i need to run that code for form2 when changes happens in OPC server.

@Shaggy Hiker, i am not sure what means "running in background", but if data of an active item in active group changes, the server calls that sub OnDataChange().

[chris128]

i need to run that code for form2 when changes happens in OPC server.

Well then you need some way of knowing when changed happen in OPC server - which I assume is what this OnDataChange event that you mentioned is for. So stick the code in the event handler for that OnDataChange event.

[Fact]

Well chris, i might be do not express myself clear enough. When some changes in OPC server occours then OPC server calls that sub OnDataChange(). This sub by default looks like that:

Overridable Sub OnDataChange( _
    ByVal dwTransid As Integer, _
    ByVal hGroup As Integer, _
    ByVal hrMasterquality As Integer, _
    ByVal hrMastererror As Integer, _
    ByVal dwCount As Integer, _
    ByVal phClientItems() As Integer, _
    ByVal pvValues() As Object, _
    ByVal pwQualities() As Short, _
    ByVal pftTimeStamps() As OpcRcw.Da.FILETIME, _
    ByVal pErrors() As Integer) Implements IOPCDataCallback.OnDataChange

End Sub

So, inside that sub i put this code to take values from OPC server and populate them in forms1 datagrid.

Dim i As Integer = 0
        Dim j As Integer = 1
        Dim k As Integer = 0

        If dwCount > 0 Then

            mObject = New List(Of Object)
            For i = 0 To jk - 1
                For j = 1 To jk
                    If phClientItems(i) = j Then
                        DataGridView1.Rows(j-1).Cells(1).Value=Convert.ToString(pvValues(k))
                        k += 1
                    End If
                Next j
            Next i
        End If

And each time some changes happens - values in forms1 datagrid changes as well (this sub is in form1). But i also want to see same chaneges in forms2 datagrid.
This sub (OnDataChange) is a part of IOPCDataCallBack which i implement in form1 class.

[chris128]

Then you need to tell form2 to do it as well - you could create a new method on Form2 called something like DataChanged and have that do the code that is required to fill Form2's datagrid, then in your OnDataChange sub on Form1 you call that DataChanged method on Form2.

Personally I would try and implement this outside of your forms (ie in a dedicated class) but depending on how this OPC component works that may not be possible in this situation

[Fact]

Well, i am not good in VB so maybe this will help you more to undrstand what i am trying to do, and at that time i will try to create a new method and put its call into OnDataChange sub.

The basic sequence of the individual program steps corresponds to the previous sample
OPC custom interface, asynchronous communication . These include establishing the
connection to the OPC server, creating a group with variables, and reading and writing
values for an item. The following table shows the steps to be executed by the program:
Step Description
1 Select .NET components
2 Convert the ProgID to a CLSID
3 Establish connection to the OPC server
4 Create an OPC group
5 Adding Items
6 Request the interface IConnectionPointContainer
7 Request the interface IOPCAsyncIO2
8 Create callback object
9 Connect OPC server and callback object of the client
10 Execute required write and read operations
11 Receive notifications of the OPC server
12 Delete objects and release memory
Step 1: Select .NET components
To use the Custom Interface for OPC Data Access with .NET, you must use the Runtime
Callable Wrapper (RCW) described above in your Visual Basic project. In the sample project,
the components OpcRcw.Da and OpcRcw.Comn have already been added.
If these do not appear in the selection, you can also select them using the Browse button
from the following folder
<installationpath>\SIEMENS\SIMATIC.NET\opc2\bin .
Sample programs
5.4 OPC Custom interface (asynchronous communication) in VB.NET
Industrial Communication with PG/PC Volume 2 - Interfaces
Programming Manual, Release 06/2008, C79000-G8976-C197-08 421
Figure 5-25 Selecting the Runtime Callable Wrapper (RCW) in the Visual Basic project
With the commands
Imports OpcRcw.Comn
Imports OpcRcw.Da
it is simple to use the name space and methods of the OPC Custom interface with .NET
Framework.
Step 2: Convert the ProgID to a type
To identify it, each COM server has a ProgID that is assigned to a worldwide unique type.
This is obtained with the GetTypeFromProgID() function. The ProgID of the OPC server of
SIMATIC NET is L"OPC.SimaticNET ":
Dim typeofOPCserver As Type =
Type.GetTypeFromProgID(L"OPC.SimaticNET")
Step 3: Establish connection to the OPC server
The CreateInstance() function of the Activator class generates an instance of the class with a
previously specified type:
m_server = Activator.CreateInstance(typeofOPCserver)
The result of this section of program is an interface variable m_server of the type
IOPCServer.
Sample programs
5.4 OPC Custom interface (asynchronous communication) in VB.NET
Industrial Communication with PG/PC Volume 2 - Interfaces
422 Programming Manual, Release 06/2008, C79000-G8976-C197-08
Step 4: Create an OPC group
The IOPCServer interface has the AddGroup() method for creating groups:
m_server.AddGroup("MyOPCGroup",
0,
250,
1,
pTimeBias,
pDeadband,
LOCALE_ID,
ServerGroup,
RevisedUpdateRate,
GetType(IOPCGroupStateMgt).GUID,
m_group)
The result of this program section is a group with the specified name and the required
properties. AddGroup() also returns a variable m_group as return parameter, an interface to
a group object, in this case IOPCGroupStateMgt. The IOPCGroupStateMgt interface is
necessary to allow use of the SetState() methods. The SetState() method is required later to
activate and deactivate a group.
By means of a simple assignment, the m_item variable of the type IOPCItemMgt can be
derived from the m_group interface variable.
m_item = m_group
Step 5: Adding Items
The IOPCItemMgt interface has the AddItems() method for creating OPC items:
m_item.AddItems(2, itemdefs, Results, pErrors)
The result of this program section is that the server adds two items with the properties
specified in the itemdefs parameter. The variables of the result structure Results (server
handle, data type of the item on the target system etc.) are also initialized.
Since the results are written to unmanaged memory by the underlying COM interface, the
access from managed .NET code must make use of the marshaling functions:
result = Marshal.PtrToStructure(pos, GetType(OPCITEMRESULT))
ServerHandle1 = result.hServer
pos = New IntPtr(pos.ToInt32() +
Marshal.SizeOf(GetType(OPCITEMRESULT)))
result = Marshal.PtrToStructure(pos, GetType(OPCITEMRESULT))
ServerHandle2 = result.hServer
The client must also make sure that the unmanaged memory is released:
Marshal.FreeCoTaskMem(Results)
Marshal.FreeCoTaskMem(pErrors)
Step 6: Request the interface IConnectionPointContainer
The m_ConnectionContainer variable of the type IConnectionPointContainer can be derived
from the m_group variable.
m_ConnectionContainer = m_group
The interface is required to locate the IConnectionPoint interface.
Sample programs
5.4 OPC Custom interface (asynchronous communication) in VB.NET
Industrial Communication with PG/PC Volume 2 - Interfaces
Programming Manual, Release 06/2008, C79000-G8976-C197-08 423
Step 7: Request the IOPCAsyncIO2 interfaces
The m_asyncIO2 variable of the type IOPCAsyncIO2 can be derived from the m_group
variable.
m_asyncIO2 = m_group
This interface provides methods for asynchronous reading and writing of values.
Step 8: Create callback object
To allow the OPC server to return a result of asynchronous operations, the
IOPCDataCallback interface must be implemented on the client.
Implements IOPCDataCallback
The connection of the IConnectionPoint interface and IOPCDataCallback of the OPC server
is established using the FindConnectionPoint() method of the IConnectionPointContainer
interface. This generates a callback object for asynchronous calls.
m_ConnectionContainer.FindConnectionPoint(
GetType(IOPCDataCallback).GUID,
m_ConnectionPoint)
Step 9: Connect OPC server and callback object of the client
The connection between the callback object of the OPC server and the client application is
established by the Advise() method. The return variable m_dwCookie is an ID for the
connection.
m_ConnectionPoint.Advise(Me, m_dwCookie)
Step 10: Execute required write or read operation
The Read() and Write() methods that were generated in Step 7 can be accessed over the
IOPCAsyncIO2 interface:
m_asyncIO2.Read(1, pServer, Transaction, CancelID, pErrors)
Step 11: Receive notifications of the OPC server
If the data of an active item in an active group changes, the server calls the OnDataChange()
method of the callback object. On completion of a read operation, the server calls the
OnReadComplete() method, on completion of a write operation, the OnWriteComplete()
method is called. The server passes the return values as parameters to the method.
Overridable Sub OnDataChange(
ByVal dwTransid As Integer,
ByVal hGroup As Integer,
ByVal hrMasterquality As Integer,
ByVal hrMastererror As Integer,
ByVal dwCount As Integer,
ByVal phClientItems() As Integer,
ByVal pvValues() As Object,
ByVal pwQualities() As Short,
ByVal pftTimeStamps() As OpcRcw.Da.FILETIME,
ByVal pErrors() As Integer) Implements
IOPCDataCallback.OnDataChange
Sample programs
5.5 OPC Custom interface (synchronous communication) in C#
Industrial Communication with PG/PC Volume 2 - Interfaces
424 Programming Manual, Release 06/2008, C79000-G8976-C197-08
Step 12: Delete objects and release memory
Before exiting the program, the OPC objects that have been created must be deleted and
the memory reserved for them must be released. The relevant functions are integral parts of
the previously used interfaces. Unadvise() terminates the connection between the OPC
server and the callback object:
m_ConnectionPoint.Unadvise(m_dwCookie)
Marshal.ReleaseComObject(m_ConnectionPoint)
m_item.RemoveItems(2, pItems, pErrors)
....
Marshal.FreeCoTaskMem(pErrors)
m_server.RemoveGroup(ServerGroup, True)
Releasing memory
When using COM, it is sometimes necessary for the client to release memory that was
requested by the server. The rules for this are as follows:
● [out]: The memory for a parameter with this attribute will be requested from the server.
● [in, out]: The memory for such a parameter will be requested from the client. The server
can release the memory again and reallocate it.
● [in]: The client will request the memory. The server is not responsible for releasing the
memory.
In all three cases, the reserved memory of unmanaged COM objects should be released by
the client.

Thank you for your patience

[Fact]

OK, i made sub in form2:

Public sub xxx ( ByVal example as object)
ListBox1.Items.Add(example)
MsgBox(example)
End Sub

And changed code in forms1 OnDataChange sub:

Public mObject As List(Of Objects) = New List(Of  Objects)
Overridable Sub OnDataChange( _
    ByVal dwTransid As Integer, _
    ByVal hGroup As Integer, _
    ByVal hrMasterquality As Integer, _
    ByVal hrMastererror As Integer, _
    ByVal dwCount As Integer, _
    ByVal phClientItems() As Integer, _
    ByVal pvValues() As Object, _
    ByVal pwQualities() As Short, _
    ByVal pftTimeStamps() As OpcRcw.Da.FILETIME, _
    ByVal pErrors() As Integer) Implements IOPCDataCallback.OnDataChange
Try
Dim i As Integer = 0
        Dim j As Integer = 1
        Dim k As Integer = 0

        If dwCount > 0 Then

            mObject = New List(Of Object)
            For i = 0 To jk - 1
                For j = 1 To jk
                    If phClientItems(i) = j Then
                        DataGridView1.Rows(j-1).Cells(1).Value=Convert.ToString(pvValues(k))
                        mObject.Add(pvValues(k))
                        k += 1
                    End If
                Next j
            Next i
        End If
Finally
Form2.xxx(mObject(0))
End Try
End Sub

Each time when data changes in OPC server - forms1 datagrid gets new data, message box shows correct value, but my forms2 ListBox remains empty. Now i am really out of imagination.

[chris128]

I notice you are using the default form instance there (as you just used Form2.xxx instead of creating a new instance of Form2 then calling xxx on that instance). Are you sure that the Form2 you are viewing on the screen is the default instance as well?

Also, have you placed that call to Form2.xxx in the Finally block of your Try/Catch code just to test with? because I dont think it is going to give you the results you expect when it is only getting called once

[Fact]

I notice you are using the default form instance there (as you just used Form2.xxx instead of creating a new instance of Form2 then calling xxx on that instance). Are you sure that the Form2 you are viewing on the screen is the default instance as well?

Yes, i think so, code of form2

Option Strict Off
Option Explicit On

Imports System.IO


Public Class Form2
    Public mObject As List(Of Object) = New List(Of Object)


    Private Sub Form2_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        DataGridView1.Columns(0).HeaderText = "Parameter"
        DataGridView1.Columns(1).HeaderText = "Value"
        DataGridView1.Columns(2).HeaderText = "Unit"
        Dim sr As StreamReader = New StreamReader("txt\viens.txt")
        Dim line As String = Nothing
        Do
            line = sr.ReadLine()
            If Not line = Nothing Then
                Dim mArray(2) As String
                mArray(0) = Split(line, "  ")(0)
                mArray(1) = ""
                mArray(2) = Split(line, "  ")(1)
                DataGridView1.Rows.Add(mArray)
            End If
        Loop Until line Is Nothing

        Dim i As Integer
        For i = 0 To Form1.mObject.Count - 1
            DataGridView1.Rows(Form1.mObject1(i) - 1).Cells(1).Value = (Form1.mObject(i))
            ListBox1.Items.Add(Form1.mObject(i))
        Next i
    End Sub

    Public Sub xxx(ByVal example As String)

       ListBox1.Items.Add(example)
    End Sub
End Class

Also, have you placed that call to Form2.xxx in the Finally block of your Try/Catch code just to test with? because I dont think it is going to give you the results you expect when it is only getting called once

It looks silly, but i put it there as i do not know where else i could put it

[Shaggy Hiker]

How are you displaying form 2? That would show us whether you are using the default instance or not.

[Fact]

If you mean how do i open form2 then here is a code in form1:

Private Sub Form2ToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Form2ToolStripMenuItem.Click
        Form2.Show()
    End Sub

[Shaggy Hiker]

Well, that's the default instance, so the sub call should be correct the way you have it.

The problem would be if you had declared an instance of Form2 with something like:

Private myFrm2 as New Form2

I notice that you are putting together a list of objects in the data arrival method, but only passing over the first object, but then, you are also just adding one item, so it is probably nearly what you want to pass.

However, since you are passing an object to a sub that is expecting a String, you probably have Option Strict Off. You may find that what is coming across is not at all what you expect to see.

The next step would be to put a breakpoint in the sub on Form2 where you add the item to the listbox. If the breakpoint is reached, execution will pause, and you can look to see what is in the argument to the sub.

After doing that, you will have these possibilities:

1) The breakpoint is never reached.
2) The breakpoint is reached, but the argument is an empty string.
3) The breakpoint is reached, and the argument is not an empty string, but it is not what you wanted.
4) The breakpoint is reached, and the argument is what you wanted.

What to do next is dependent on which of those four is the right one.

[Fact]

Well, i hope i did correctly what you said and when this line in form1

Form2.xxx(mObject(0))

becomes highlighted (yellow) and the value of mObject(0) is the one that should be.

EDITED:
After that line becomes yellow and i press F10 form2 sub xxx becomes yellow and the value of variable example is the same as mObject(0), and after that it returns back to form1 line Form2.xxx(mObject(0)) that line becomes gray, but nothing is added to listbox.

[Shaggy Hiker]

That wasn't the line I wanted the breakpoint on. Put it on this line from the sub in Form2:

ListBox1.Items.Add(example)

Have no other breakpoints.

From what you have said, it sounds like you will end up with situation 4. If that is the case, the one other thing that might be an easy answer would be to add the line:

Listbox1.Refresh

after the item is added.

However, give that a try, and see whether example is, in fact, what you expect it to be.

[Fact]

I did that but listbox is empty. After line ListBox1.Items.Add(exmple) i put line MsgBox(example) and the message box with correct value showed up.

[Shaggy Hiker]

Ok, I think you have completely covered the fact that the listbox should be getting something, yet it is not displaying anything. This leads to one of a variety of possibilities.

First off, try this:

You have shown the Load event for Form2. Put something into the listbox during the load event. It doesn't matter what, just some random string will be fine. Does that show up?

If that string does not show up, then you are seeing the wrong form. Why that is I can't say, as I see no reason for it from what you have shown. The most typical reason for that is because you are changing the default instance, but not showing the default instance. However, you showed how you are showing the form, and you are showing the default instance, as well, so that should not be the answer.

If the string does show up, then I suspect that your data arrival is running in a background thread. I have never tried messing with that, but I seem to remember JM mentioning something about a control in a background thread not displaying in the UI thread. On the other hand, that doesn't seem right, either, as you are not creating the control in the background thread, so adding to it from a background thread should cause an IllegalCrossThread exception.

Either way, I must say that I am stumped. From what you have shown so far, I see no good reason why the item is not showing up.

[Fact]

OK, in form2 load event i put line ListBox1.Items.Add(Form1.mObjetc(0)) and i got into listbox first value from OPC server, and that is good.

[Shaggy Hiker]

I think you may not be on the thread you think you are on. I don't have enough experience with this to be sure whether or not what you are seeing is a result of your call to the sub happening on a background thread, but I think it is reasonably likely.

One alternative you might try would be something like what I do in post #2 of this thread using a SynchronizationContext:

http://www.vbforums.com/showthread.p...zation+context

Save the SynchronizationContext early on, when you are clearly in the UI thread, though it doesn't really matter where you save it, though it should probably be on Form1.

Then, look at Posting a call to the SynchronizationContext that you saved. It's a pretty simple means of ensuring that your call is happening on the UI thread. It might solve your problem, or it might miss the mark.

[Fact]

OK, thank you for being patience with me, Shaggy Hiker, +karma
I will check the alternative you suggest.

[Fact]

Well Shaggy Hiker, i have read your post, but as i am not good enough in visual basic i hardly can understand things there.
Maybe somebody has more solutions what is wrong here?

[Fact]

OK, i think i found what is wrong, but don't know how to fix.
In form 2 i made a public sub

Public Sub xxx(ByRef example As Object)

        TextBox1.Text = Convert.ToString(example)

    End Sub

And put a breake point at it.
In form1, sub OnDataChange, after Try i put code

Form2.xxx(mObject(0))

and put breake point at line Try.
After debugger started program stopped on line Try in form1. On next line

Form2.xxx(mObject(0))

i put mouse cursor on mOject(0) and saw that it contains value:

mObject Count=1
(0)  45 {UInteger}

After that line

Public Sub xxx(ByRef example As Object)

in form2 became highlighted, and value of example is

example  45  {UInteger}

Jump on line

TextBox1.Text = Convert.ToString(example)

gave me

TextBox1.Text  ""
exmple: 45  {UInteger}

After jump to line End Sub, the values are

TextBox1.Text  "45"
exmple: 45  {UInteger}

Then it returned to form1 line

Form2.xxx(mObject(0))

and the value of mObject(0) there is

mObject Count=1
(0)  45 {UInteger}

But i decided to check what value contains TextBox1 in form2, so went back to form2, put mouse pointer on the TextBox1.Text in line

TextBox1.Text = Convert.ToString(example)

and saw:

TextBox.Text1 { "An exception 'Microsoft.VisualStudio.Debugger.Runtime.CrossThreadMessagingException' occurred"}

StackTrace

StackTrace = "   at Microsoft.VisualStudio.Debugger.Runtime.Main.ThrowCrossThreadMessageException(String formatString)    at System.Windows.Forms.SafeNativeMethods.GetWindowTextLength(HandleRef hWnd)    at System.Windows.Forms.Control.get_WindowText()    at System.Windo...

I believe that is the problem why textbox remains empty in form2. Does anybody has any clue how can i fix it?

[chris128]

It means you are accessing that control from a thread that does not 'own' it. Basically you should not modify any controls from a background thread, it should be done from the UI thread. You can use JMC's tutorial here to learn how to work around this: http://www.vbforums.com/showthread.php?t=498387

[Fact]

Well, i have tried that as well, but with no luck
Form2

Public Delegate Sub SetTextBoxTextInvoker(ByVal text As String)
    Public Sub SetTextBoxText(ByVal text As String)

        If TextBox1.InvokeRequired Then

            TextBox1.Invoke(New SetTextBoxTextInvoker(AddressOf SetTextBoxText), text)
        Else
            TextBox1.Text = text
        End If
    End Sub

Form1

Finally
            Form2.SetTextBoxText(mObject(0))
End Try

Is that code correct?

[chris128]

I think that should work yes, but the way I have always done it in the past is to use two separate methods, so for example:

Public Sub SetTextBoxText(ByVal text As String)
      TextBox1.Invoke(New SetTextBoxTextInvoker(AddressOf InvokedSetTextBoxText), text)
End Sub
 
Private Sub InvokedSetTextBoxText(ByVal text As String)
      TextBox1.Text = text
End Sub

Like I said though, I think the way you are currently doing it should still work...

[Fact]

Well, result is the same - empty textbox in form2. I even do not understand, why do i need this code

Public Delegate Sub SetTextBoxTextInvoker(ByVal text As String)
    Public Sub SetTextBoxText(ByVal text As String)

        If TextBox1.InvokeRequired Then

            TextBox1.Invoke(New SetTextBoxTextInvoker(AddressOf SetTextBoxText), text)
        Else
            TextBox1.Text = text
        End If
    End Sub

i put a break point on this sub and saw that program comes to if and jumps to else, so it makes same as mine sub

Public Sub xxx(ByVal example As Object)

        TextBox1.Text = Convert.ToString(example)

    End Sub

[Fact]

After long experiments i came up to the dead end. I decided to clean up that OnDataChange sub and simply put code that each time when something changes in OPC server i will get an message box, with a first value.

Overridable Sub OnDataChange( _
    ByVal dwTransid As Integer, _
    ByVal hGroup As Integer, _
    ByVal hrMasterquality As Integer, _
    ByVal hrMastererror As Integer, _
    ByVal dwCount As Integer, _
    ByVal phClientItems() As Integer, _
    ByVal pvValues() As Object, _
    ByVal pwQualities() As Short, _
    ByVal pftTimeStamps() As OpcRcw.Da.FILETIME, _
    ByVal pErrors() As Integer) Implements IOPCDataCallback.OnDataChange
If dwCount > 0 Then
            MsgBox(pvValues(0))
        End If
        dwCount = 0

    End Sub

So each time OPC server calls that sub i get a message box with the first value. After that i decided to make so that after each change i get value in the texbox that is on form1, but textbox remains empty all the time.

Overridable Sub OnDataChange( _
    ByVal dwTransid As Integer, _
    ByVal hGroup As Integer, _
    ByVal hrMasterquality As Integer, _
    ByVal hrMastererror As Integer, _
    ByVal dwCount As Integer, _
    ByVal phClientItems() As Integer, _
    ByVal pvValues() As Object, _
    ByVal pwQualities() As Short, _
    ByVal pftTimeStamps() As OpcRcw.Da.FILETIME, _
    ByVal pErrors() As Integer) Implements IOPCDataCallback.OnDataChange
If dwCount > 0 Then
            MsgBox(pvValues(0))
            TextBox1.Text = Convert.ToString(pvValues(0))
        End If
        dwCount = 0

    End Sub

I have checked what is wrong, and as Chris128 said it was

It means you are accessing that control from a thread that does not 'own' it.

Fine, i put those two lines in my code and textbox on form1 started to work (same thing with ListBox, RichTextBox and so on).

Overridable Sub OnDataChange( _
    ByVal dwTransid As Integer, _
    ByVal hGroup As Integer, _
    ByVal hrMasterquality As Integer, _
    ByVal hrMastererror As Integer, _
    ByVal dwCount As Integer, _
    ByVal phClientItems() As Integer, _
    ByVal pvValues() As Object, _
    ByVal pwQualities() As Short, _
    ByVal pftTimeStamps() As OpcRcw.Da.FILETIME, _
    ByVal pErrors() As Integer) Implements IOPCDataCallback.OnDataChange
If dwCount > 0 Then
            MsgBox(pvValues(0))
            ThreadExceptionDialog.CheckForIllegalCrossThreadCalls = False
            TextBox1.Text = Convert.ToString(pvValues(0))
            ThreadExceptionDialog.CheckForIllegalCrossThreadCalls = True
        End If
        dwCount = 0
    End Sub

It would be good, but how then i can make to work textbox on form2?
Beg for ideas, or my head will explode

[chris128]

All you are doing there is just hiding the exceptions by setting CheckForIllegalCrossThreadCalls to false... Those exceptions are thrown for a reason, just hiding them instead of actually fixing the problem is going to cause you more problems in the future

[Fact]

OK, i made things like that

Form1
Private Delegate Sub yyyInvoker(ByVal mString As String)
    Private Sub yyy(ByVal mString As String)
        If TextBox1.InvokeRequired Then
            TextBox1.Invoke(New yyyInvoker(AddressOf yyy), mString)
        Else
            TextBox1.Text = mString
        End If
    End Sub
 Overridable Sub OnDataChange(...........................)
        If dwCount > 0 Then
            yyy(pvValues(0))
        End If
        dwCount = 0
    End Sub

When the program comes to line

If TextBox1.InvokeRequired Then

I see

TextBox1.InvokeRequired True

and textbox in form1 is filled with a value from OPC server, HYRRAY!
So i made similar sub in form2

Form2
Public Delegate Sub xxxInvoker(ByVal qString As String)
    Public Sub xxx(ByVal qString As String)
        If TextBox1.InvokeRequired Then
            TextBox1.Invoke(New xxxInvoker(AddressOf xxx), qString)
        Else
            TextBox1.Text = qString
        End If
    End Sub

and put a call into form1

Form1
Overridable Sub OnDataChange(...........................)
If dwCount > 0 Then
            yyy(pvValues(0))
            Form2.xxx(pvValues(0))
        End If
        dwCount = 0
    End Sub

when program comes to line in form2

If TextBox1.InvokeRequired Then

i see that

TextBox1.InvokeRequired  False

and textbox in form2 remains empty.
Any comments on that?

[chris128]

Hmm that does sound odd - is there any chance you could post your full solution here as an attachment to your post?

[Fact]

Yes sure, here it is, the strange thing is that it says, that invokerequired False.
Maybe it is not possible to do what i want.

[chris128]

Firstly, turn Option Strict on!

Anyway - I'll take a look through your code now and see if I can see anything

[Fact]

In the SIEMENS sample it is shown as Strict off.

[chris128]

Then they are not very good VB.NET programmers... There is no good reason to have Option Strict off, it just means you have a little bit less to type and can be less careful with casting and converting, which then results in problems a lot of the time. Turn it on and fix all of the problems that it highlights and then see if you are still having problems.
I looked at your code but at the moment it is so messy (presumably from you trying out lots of different things) that it is quite hard to see what is going on. Also, I do not know what this OPC thing does or how the OnDataChanged method gets called so it is hard for me to test it. I tested just calling that OnDataChanged method from a button click and passing in some random parameters but it all worked fine and the textbox on both Form1 and Form2 was filled in.

[Fact]

Well chris128, you did a great job, i am really appreciate that!

Then they are not very good VB.NET programmers...

Unfortunetaly i am much worser then they are, that is fact

Here is a piece of information how this OnDataChange works, maybe it will be usefull for you in some future

To allow the OPC server to return a result of asynchronous operations, the
IOPCDataCallback interface must be implemented on the client.
Implements IOPCDataCallback
The connection of the IConnectionPoint interface and IOPCDataCallback of the OPC server
is established using the FindConnectionPoint() method of the IConnectionPointContainer
interface. This generates a callback object for asynchronous calls.
m_ConnectionContainer.FindConnectionPoint(
GetType(IOPCDataCallback).GUID,
m_ConnectionPoint)
The connection between the callback object of the OPC server and the client application is
established by the Advise() method. The return variable m_dwCookie is an ID for the
connection.
m_ConnectionPoint.Advise(Me, m_dwCookie)
method of the callback object. On completion of a read operation, the server calls the
OnReadComplete() method, on completion of a write operation, the OnWriteComplete()
method is called. The server passes the return values as parameters to the method.
Overridable Sub OnDataChange(
ByVal dwTransid As Integer,
ByVal hGroup As Integer,
ByVal hrMasterquality As Integer,
ByVal hrMastererror As Integer,
ByVal dwCount As Integer,
ByVal phClientItems() As Integer,
ByVal pvValues() As Object,
ByVal pwQualities() As Short,
ByVal pftTimeStamps() As OpcRcw.Da.FILETIME,
ByVal pErrors() As Integer) Implements
IOPCDataCallback.OnDataChange

I will try to start it all fom the empty list, if i succeed i will post the result, if not - well, then i will be in need to give up.
Here is a small gift from me

Once more time thank you very much for all you did.

[chris128]

haha thank you for the massively oversized beer

What exactly does this OPC server thing do? I mean is there any way I could test it in the same way you are testing it? Does it require any special equipment or anything like that?