"object instance not set to an instance of an object vb.net" happens when switch form

i have these 2 lines of code causing problem "object instance not set to an instance of an object vb.net" :

                dim frm2 as new frm2
                frm2.DsGetAllQs.Clear()
                frm2.SqlDataAdapterGetAllQs.Fill(frm2.DsGetAllQs)

i have frmStart, frm1, and frm2.
In frmStart, i have a btnStart contains code: frm1.show, me.hide
In frm1, i have the code above to be executed when itself is shown. when first time the btnStart is clicked, the code in frm1 execute fine. also on frm1 i have btnGoToFrm2 which contains code frm2.show, me.hide
In frm2, i have a btnReturn contains code: frm1.show, me.hide. when i click on btnReturn, frm2 is hide and frm1 is shown.
Now if i click on btnGoToFrm2 on frm1 again, a message shows: "object instance not set to an instance of an object vb.net". beside this message, everything will still work as expected.
I located the error source, which is the code on the top. Can anyone help plz
btw, the DsGetAllQs and SqlDataAdapterGetAllQs are visually dropped on to frm2 in design view

i checked everything, from my limited knowledge, i cant figure it out, plz help
However, nothing is actually affected by the error message, so... if you cant figure it out either, maybe you can suggest a way to hide the messge

frm2 code (full) and frm1 code (partial), the frm2 is actually called frmTesting1, frm1 is frmTestList
on datamodule(moduleUser), i have:
Public frmTestList1 As New frmTestList
Public frmTesting1 As New frmTesting

i dont know how to post a txt file with my code here.......

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"object instance not set to an instance of an object vb.net" happens when switch form

Mr pinchy

hi Sunder, I failed to email the zipped project to u, seems that it's rejected. plz indicate another way that i can pass it to u.

regards!
Mark Tomlinson - MSFT

hi KathTam:

i use (VS 2002/2003), it seems to be the problem of the dataset, becasue the error occurs on the line of dataset.clear()
bennykfc

thx very very much kathtam, here is the code in both forms that might be causing the problem, the blue colored code is my identified problem area:

frm1:

---------------------------------------------------------------------------------------------------------

Private Sub btnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.Click
        Try
            ModuleUser.frmTesting1.Show()

            'initialize time elements for result
            iniDateTimes()

            If (isTest = True) And (ModuleUser.curTest <> Nothing) Then     'if is a test then start test
                startTest() 'start current test
            Else
                'if not a test, gives error
                MsgBox("No test selected" & vbNewLine & "Please selecte a test!")
            End If

        Catch Exp As SqlClient.SqlException
            MsgBox(Exp.Message, MsgBoxStyle.Critical, "SQL Error")

        Catch Exp As Exception
            MsgBox(Exp.Message, MsgBoxStyle.Critical, "General Error")
        End Try

    End Sub

    Private Sub iniDateTimes()

        'initialize time elements for result
        If ModuleUser.startDate <> Nothing Then
            ModuleUser.startDate = Nothing
        End If

        If ModuleUser.startTime <> Nothing Then
            ModuleUser.startTime = Nothing
        End If

        If ModuleUser.endDate <> Nothing Then
            ModuleUser.endDate = Nothing
        End If

        If ModuleUser.endTime <> Nothing Then
            ModuleUser.endTime = Nothing
        End If

    End Sub

    Private Sub startTest()

        Try
            If Not SqlConnectionTest.State = ConnectionState.Open Then
                SqlConnectionTest.Open()
            End If
            'check if test has questions or not
            SqlCommandDoesTestHaveQ.Parameters("@TNAME").Value = ModuleUser.curTest

            If SqlCommandDoesTestHaveQ.ExecuteScalar() = 0 Then
                'if test doent have questions, deny testing
                MessageBox.Show("Testing Denied!" & vbNewLine & "Test is empty, please add questions to the test first!", "Testing", MessageBoxButtons.OK, MessageBoxIcon.Information)
            Else
                'if test has questions, start testing
                'get frmTesting1 caption
                ModuleUser.frmTesting1.Text = "Testing:   " & ModuleUser.curTest

                'execute the test
                If ModuleUser.frmTesting1.SqlConnectionTesting.State = ConnectionState.Closed Then
                    ModuleUser.frmTesting1.SqlConnectionTesting.Open()
                End If
                'get current TID for reference
                ModuleUser.frmTesting1.SqlCommandGetTID.Parameters("@TNAME").Value = ModuleUser.curTest

                'get total number of questions for the label
                ModuleUser.frmTesting1.SqlCommandTotalQs.Parameters("@TID").Value = ModuleUser.frmTesting1.SqlCommandGetTID.ExecuteScalar().ToString()
                ModuleUser.frmTesting1.lblTotalQs.Text = ModuleUser.frmTesting1.SqlCommandTotalQs.ExecuteScalar().ToString()

                'fill question textbox with first record
                ModuleUser.frmTesting1.SqlCommandGetQDetails.Parameters("@TID").Value = ModuleUser.frmTesting1.SqlCommandGetTID.ExecuteScalar().ToString()
                ModuleUser.frmTesting1.RTBQuestion.Text = ModuleUser.frmTesting1.SqlCommandGetQDetails.ExecuteScalar().ToString()

                'empty answer textbox
                ModuleUser.frmTesting1.RTBAnswer.Text = Nothing

                'get full marks for current test and fill into lblFullMarks.text
                ModuleUser.frmTesting1.SqlCommandFullMarks.Parameters("@TID").Value = ModuleUser.frmTesting1.SqlCommandGetTID.ExecuteScalar().ToString()
                ModuleUser.frmTesting1.lblFullMarks.Text = ModuleUser.frmTesting1.SqlCommandFullMarks.ExecuteScalar().ToString()

                'fill the questions list
                ModuleUser.frmTesting1.SqlSelectCommandGetAllQs.Parameters("@TID").Value = ModuleUser.frmTesting1.SqlCommandGetTID.ExecuteScalar().ToString()

                '----------------------------------------
                'No problem before this point
                '----------------------------------------

                ModuleUser.frmTesting1.DsGetAllQs.Clear()

                ModuleUser.frmTesting1.SqlDataAdapterGetAllQs.Fill(ModuleUser.frmTesting1.DsGetAllQs)

                '----------------------------------------
                'problem is before this point'
                '----------------------------------------

                'display make-up question numbers in question number list
                ModuleUser.frmTesting1.ListBoxQNum.Items.Clear()
                Dim i As Integer
                For i = 1 To ModuleUser.frmTesting1.SqlCommandTotalQs.ExecuteScalar().ToString()
                    ModuleUser.frmTesting1.ListBoxQNum.Items.Add(i)
                Next

                'get UID for reference
                ModuleUser.frmTesting1.SqlCommandGetUID.Parameters("@UNAME").Value = ModuleUser.userName

                'add new result for the testing
                ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@TID").Value = ModuleUser.frmTesting1.SqlCommandGetTID.ExecuteScalar().ToString()
                ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@UID").Value = ModuleUser.frmTesting1.SqlCommandGetUID.ExecuteScalar().ToString()
                ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@STARTDATE").Value = Now.ToLongDateString()
                ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@STARTTIME").Value = Now.ToLongTimeString()
                ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@ENDDATE").Value = Now.ToLongDateString()
                ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@ENDTIME").Value = Now.ToLongTimeString()
                ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@TOTALMARKS").Value = 0
                ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@GRADE").Value = "FAILED"
                ModuleUser.frmTesting1.SqlCommandAddResult.ExecuteNonQuery()

                'get current RID for reference
                ModuleUser.frmTesting1.SqlCommandGetCurRID.Parameters("@STARTTIME").Value = ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@STARTTIME").Value
                ModuleUser.frmTesting1.SqlCommandGetCurRID.Parameters("@ENDTIME").Value = ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@ENDTIME").Value
                ModuleUser.curResultID = ModuleUser.frmTesting1.SqlCommandGetCurRID.ExecuteScalar().ToString()

                'get time elements' values for result
                ModuleUser.startDate = ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@STARTDATE").Value
                ModuleUser.startTime = ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@STARTTIME").Value
                ModuleUser.endDate = ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@ENDDATE").Value
                ModuleUser.endTime = ModuleUser.frmTesting1.SqlCommandAddResult.Parameters("@ENDTIME").Value

                ModuleUser.frmTesting1.SqlConnectionTesting.Close()

                Me.Hide()

                SqlConnectionTest.Close()
            End If

        Catch Exp As SqlClient.SqlException
            MsgBox(Exp.Message, MsgBoxStyle.Critical, "SQL Error")

        Catch Exp As Exception
            MsgBox(Exp.Message, MsgBoxStyle.Critical, "General Error")
        End Try

    End Sub

---------------------------------------------------------------------------------------------------
flinxperbil

You can ignore the exception by doing the following

Dim frm2 As New frm2

Try

frm2.DsGetAllQs.Clear()

frm2.SqlDataAdapterGetAllQs.Fill(frm2.DsGetAllQs)

Catch ex As System.NullReferenceException

'ignore

End Try

However- it would be nice to understand why the code is throwing the Exception in the first place. You mention that you can't post the text file here so I need to know a bit more information (Besides the explaination you gave above)

Exactly which line again, was the error occuring on it's possible that you need to wait for Form2 (frm2) to finish initializing and if that is the case, I can help supply some code to do this.

thanks in advance,
Render

thx Sunder, It's very kind of u :)

now I am using .net2005, i converted the project in .net2005, however, yes, the problem still persists, I "grayed out" the buttons so that this function is not accessable by users (what a silly way)

plz look at frmResult and frmTesting, there are 2 pink-colored buttons with the same problem.

btw, sorry for the messy code, it's my first vb.net project :)

the db file is also attached, you can either copy the db file or recover from the backup device. I found recover from backup device is easier.

plz comment on any stupid code.

I am trying to send the zipped project along with the db through to ur email adress, hope they can reach u, thx again.
Chris Clements

frm2:

---------------------------------------------------------------------------------------------------

   Private Sub btnGiveUp_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGiveUp.Click
        If MsgBox("Are you sure to quit this test ", MsgBoxStyle.YesNo) = MsgBoxResult.Yes Then
            giveUpCurrentTest()
        End If
    End Sub

    Private Sub giveUpCurrentTest()
        Try
            If SqlConnectionTesting.State = ConnectionState.Closed Then
                SqlConnectionTesting.Open()
            End If
            'confirm with user "are you sure to give up "
            'if yes, then remove current result and all atqs

            MessageBox.Show("Testing terminated!", "Give up test", MessageBoxButtons.OK, MessageBoxIcon.Information)

            'remove all ATQs
            SqlDeleteCommandAllATQs.Parameters("@RID").Value = ModuleUser.curResultID
            SqlDeleteCommandAllATQs.ExecuteNonQuery()

            'remove current result
            SqlCommandRemoveCurResult.Parameters("@RID").Value = ModuleUser.curResultID
            SqlCommandRemoveCurResult.ExecuteNonQuery()

            ModuleUser.curResultID = Nothing
            ModuleUser.startDate = Nothing
            ModuleUser.startTime = Nothing
            ModuleUser.endDate = Nothing
            ModuleUser.endTime = Nothing

            'return to test list
            ModuleUser.frmTesting1.Show()
            Me.Hide()
            ModuleUser.frmTestList1.iniFormTestList()

            SqlConnectionTesting.Close()

        Catch Exp As SqlClient.SqlException
            MsgBox(Exp.Message, MsgBoxStyle.Critical, "SQL Error")

        Catch Exp As Exception
            MsgBox(Exp.Message, MsgBoxStyle.Critical, "General Error")
        End Try
    End Sub

    Private Sub frmTesting_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
        If (MessageBox.Show("Are you sure to quite the program ", "Closing", MessageBoxButtons.OKCancel, MessageBoxIcon.Question) = Windows.Forms.DialogResult.Cancel) Then
            'dont want to quite, stay still
            e.Cancel = True

        ElseIf (MsgBox("Are you sure to quit this test ", MsgBoxStyle.YesNo) = MsgBoxResult.Yes) Then
            'decide to give up the test and quite
            giveUpCurrentTest()
            Application.Exit()
        Else
            'dont want to quite, stay still
            e.Cancel = True
        End If
    End Sub

------------------------------------------------------------------------------------------------

btw, i applied the catch clause you provided, however, the error msg still shows.

thx again for ur patience and help
Orf Quarenghi

if i eventually cant fix the problem, can anyone help me on totally ignore the error message i.e. stop the message popping up at runtime.
Latso
Hello

Are you still having the problem Is it possible to zip your project and send it to us

Thanks

Sunder

VB.Net
Luke B
Hello

Please email it to my Yahoo acct sundetnv@yahoo.com

Thanks

Sunder

VB.net
BMONSTER

the "SqlDataAdapterGetAllQs " is visually dropped on the frmTesting in design view, how come frm1 doenst recognize it

I tried this:
Dim SqlDataAdapterGetAllQs1 As new ModuleUser.frmTesting.SqlDataAdapterGetAllQs

It gave me this: type ModuleUser.frmTesting.SqlDataAdapterGetAllQs is not defined.

What can i do now if the object SqlDataAdapterGetAllQs is created on frmTesting visually just like a button or a textbox, it should stay there all the time when the frmTesting exists.
IvanP
ModuleUser.frmTesting1.SqlDataAdapterGetAllQs.Fill(ModuleUser.frmTesting1.DsGetAllQs)

this line is causing the problem exactly. but dont know why........
Quirk

Hi there

Could you let me know if you're using the new TableAdapter (2005) or if you are using the old SqlDataAdapter (VS 2002/2003)

There could be a possiblity that your SqlDataAdapter is not configured properly. You can verify this by bringing up the Preview Dialog at design time and then filling in the dataset...

Let me know

thanks!
"object instance not set to an instance of an object vb.net" happens when switch form

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