[RESOLVED] strange issue code dos not continue

[new1]

i have this code in BackgroundWorker to fill datagridview

Dim sql As String = "select bot.trigger,bot.verse,bot.verse1 from bot"
        Dim Adapter As New OleDbDataAdapter(sql, CON)
        Dim table As New DataTable
        Adapter.Fill(table)
        CON.Close()
        DataGridView2.DataSource = table

the problem is after Dim table As New DataTable the code dos not continue to next line and exit the BackgroundWorker1 sub

but when i put messagebox.show("") before Dim table As New DataTable the code continue and fill the datagrid

and solution for this strange issue

[.paul.]

Dim sql As String = "select trigger, verse, verse1 from bot

[new1]

same issue

[new1]

i fixed it
in vs2013 it was work in

Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
 
    End Sub

but i did change it to

Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
 
    End Sub

and now it work fine

[.paul.]

If your code crashes after Adaptor.Fill(table), there is either an error in your sql string, or an error in your connection string.
Check your field names are correct, your table name is correct, and check your connection string...

[.paul.]

The problem was referencing UI controls from a secondary thread.

[new1]

my application were not crashing at all
when i put the code in form load it fill that datagridview but when i put it in BackgroundWorker1_DoWork
it start but without filling the datagridview

what do you mean The problem was referencing UI controls from a secondary thread

[.paul.]

The BackGroundWorker_DoWork sub does not run on the same thread as the form which runs on what is known as the UI (user interface) thread. The BackGroundWorker_RunWorkerCompleted sub runs on the UI thread.

The problem was referencing controls cross thread, meaning the form's controls are not accessible on the BackGroundWorker thread without invoking them on that thread.

Try googling BackGroundWorker amd cross threading

[new1]

i see so how can i fix referencing UI controls from a secondary thread

[.paul.]

Add this code to your form:

Private Delegate Sub setDGVDataSourceCallBack(ByVal source As Object)
Private Sub setDGVDataSource(ByVal source As Object)
    If DataGridView2.InvokeRequired Then
        DataGridView2.Invoke(New setDGVDataSourceCallBack(AddressOf setDGVDataSource), source)
    Else
        DataGridView2.DataSource = source
    End If
End Sub

Then instead of:

DataGridView2.DataSource = table

Use:

setDGVDataSource(table)

[.paul.]

If you search the VB.Net CodeBank, jmcilhinney has some more in depth explanations for this topic...

[new1]

but that wont be in another thread..the reason i made it load in BackGroundWorker is because it too big access database too many records and i wont my application to take long while starting

so is there any way to make BackGroundWorker work normal again without add the fill to form thread

[new1]

i tried that but same that DGV dos not fill

Private Sub setDGVDataSource(ByVal source As Object)
        If DataGridView2.InvokeRequired Then
            DataGridView2.Invoke(New setDGVDataSourceCallBack(AddressOf setDGVDataSource), source)
        Else
            DataGridView2.DataSource = source
        End If
    End Sub
    Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        Dim sql As String = "select bot.trigger,bot.verse,bot.verse1 from bot"
        Dim Adapter As New OleDbDataAdapter(sql, CON)
        Dim table As New DataTable
        Adapter.Fill(table)
        CON.Close()
        setDGVDataSource(table)
    End Sub

[new1]

how about using the BackgroundWorker.ReportProgress method and attaching an appropriate handler to the BackgroundWorker.ProgressChanged event

[new1]

Private Delegate Sub setDGVDataSourceCallBack(ByVal source As Object)
    Private Sub setDGVDataSource(ByVal source As Object)
        If DataGridView2.InvokeRequired Then
            DataGridView2.Invoke(New setDGVDataSourceCallBack(AddressOf setDGVDataSource), source)
        Else
            DataGridView2.DataSource = source
        End If
    End Sub
    Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        Try
            Dim sql As String = "select trigger,verse,verse1 from bot"
            Dim Adapter As New OleDbDataAdapter(sql, CON)
            Dim table As New DataTable
            Adapter.Fill(table)
            CON.Close()
            setDGVDataSource(table)
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub

Error : object reference not set to an instance of an object
it show the error for Dim table As New DataTable i changed it to table1111 and still the same error

[new1]

i think the problem is in my application
i tried the code in new test application it work fine
but dos not work in original application
is there away to fix it

[.paul.]

You misunderstood me:

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        BackgroundWorker1.RunWorkerAsync()
    End Sub

    Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        Dim sql As String = "select bot.trigger,bot.verse,bot.verse1 from bot"
        Dim Adapter As New OleDbDataAdapter(sql, CON)
        Dim table As New DataTable
        Adapter.Fill(table)
        CON.Close()
        setDGVDataSource(table)
    End Sub

    Private Delegate Sub setDGVDataSourceCallBack(ByVal source As Object)
    Private Sub setDGVDataSource(ByVal source As Object)
        If DataGridView2.InvokeRequired Then
            DataGridView2.Invoke(New setDGVDataSourceCallBack(AddressOf setDGVDataSource), source)
        Else
            DataGridView2.DataSource = source
        End If
    End Sub

End Class

[new1]

ok when i use BackgroundWorker1.RunWorkerAsync() in button sub it work although the program freeze for about 7 sec which it dos not suppose to

but when i put BackgroundWorker1.RunWorkerAsync() in the form load even it give me the error : object reference not set to an instance of an object

any way to make it work from form load event without the error or freeze the application

[.paul.]

Try putting it in Form_Shown

[new1]

i tried something and it work fine i just move BackgroundWorker1.RunWorkerAsync() up to the first line in the form load event and it work fine now but the issue it it freeze the application for 6 to 7 sec is this suppose to happen? any way to fix the delay

[.paul.]

There's obviously something time consuming which is affecting your UI thread.
There are ways to improve performance, but we need to see the full code...

[new1]

the full code for form load event? or the full code for my application

the form load normally but when i switch to the DGV tap then the application freeze till it load

[.paul.]

Is Form1 the startup Form?
If yes you could use the constructor:

Public Class Form1

    Public Sub New()

        ' This call is required by the Windows Form Designer.
        InitializeComponent()

        ' Put your DGV loading code here

    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        ' put your other loading code here
    End Sub

End Class

[.paul.]

In the scenario I described, you wouldn't use a BackGroundWorker.
If your DGV is in a TabControl TabPage, it loads differently to how you'd expect, but try the constructor idea first...

[new1]

the delay cause because autosizecolum were set for all cells and it was was big data in the DGV that what cause the delay i change it to non and it load fast without freezing the application

but what do you mean with i wouldn't use a BackGroundWorker.
If your DGV is in a TabControl TabPage, it loads differently to how i'd expect

[.paul.]

If you load the dgv in sub new, it'll be loaded by the time the form first loads.

[new1]

so what is the right way to load it

[.paul.]

Public Class Form1

    Public Sub New()

        ' This call is required by the Windows Form Designer.
        InitializeComponent()

        ' Put your DGV loading code here
        Dim sql As String = "select bot.trigger,bot.verse,bot.verse1 from bot"
        Dim Adapter As New OleDbDataAdapter(sql, CON)
        Dim table As New DataTable
        Adapter.Fill(table)
        CON.Close()
        DataGridView2.DataSource = table

    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        ' put your other loading code here
    End Sub

End Class

[new1]

i used the background worker so that loading the data into the DGV wont make application start take long or freeze ..dos that code do the same?