VB.Net Allow A Certain Amount of Time To Complete A Task

Question

I'm trying to give my program a set amount of time to establish a connection with a remote drive before it fails, but I'm struggling to understand the different options available. I've tried timers and such, but the program still hangs on the section where the database is being contacted. I've researched and read that I need to run a background worker, or run it in another thread, but this is beyond my understanding at the moment.

Here's what I have so far:

    Public Sub Initialise_View()
        Dim I As Integer = 0
        Dim Fault As Boolean = False
        Main.VIEW_SavingMessage.Visible = False

        Main.VIEW_Title.Text = "Establishing Connecion To Database... Please Wait"
        Main.Refresh()

        DataGridView_Setup.Set_Datasource(0) 'This subroutine opens a connection to
    'the database and will pass a fault variable back if the database is not found,
    'however this hangs for ages if the system is having trouble accessing the
    'network drive, upwards of 5mins sometimes!


        If Fault = True Then Main.VIEW_Title.Text = "Error In Connection..."
        Main.Refresh()

    End Sub

What I'd really like is something like:

    If Connection is not established within 30 seconds Then
         Msgbox "Error, Unable to establish connection"
         Exit Sub
    End If

Which would be easy, using a timer, as long as the program didn't hang when trying to actually connect.

So my question is, is there any way around this? If so, what's the best way of going about it?

TIA

**Update**

Following Answers, I have updated to the following:

Imports System.Threading

Module View_Initialise
    Public t1 As Threading.Thread
    Public Sub Initialise_View()
        Main.Timer1.Interval = 20 * 1000
        Main.Timer1.Start()

        t1 = New Thread(New ThreadStart(AddressOf Run_Datasource))
        t1.Start()

    End Sub

    Public Sub Run_Datasource()
        Dim I As Integer = 0
        Dim Fault As Boolean = False
        Main.VIEW_SavingMessage.Visible = False

        Main.VIEW_Title.Text = "Establishing Connecion To Database... Please Wait"
        Main.Refresh()

        DataGridView_Setup.Set_Datasource(0)
        DataGridView_Setup.BindingUpdates()

        If Fault = True Then Main.VIEW_Title.Text = "Error In Connection..."
        Main.Refresh()
    End Sub



End Module

This appears to be working, as it does fire all codes ect, but the Set_Datasource(0) routine is not firing correctly, in parts of the code that tell the userform to update with information, this is not happening. Here's the code from the Set_Datasource(0): (Sorry, Its lenghtly)

  Public Sub Set_Datasource(mode As Integer)

        Try
            Main.DataGridView1.DataSource.clear()
        Catch ex As Exception

        End Try

        Dim connString As String = My.Settings.Database_String
        Dim myConnection As OleDbConnection = New OleDbConnection
        myConnection.ConnectionString = connString
        ' create a data adapter 
        Dim da As OleDbDataAdapter = New OleDbDataAdapter("SELECT ID, [Name Of Person], [SAP Job Number], [Site Name], [Asset Description], [Spares Supplier], [Supplier Contact Name], [Supplier Contact Phone Number], [Supplier Contact Email], [Spares Description], [Part Number], [Quantity To Order], Cost, [Comments], [Request Date], [Date Ordered], [Ordered By], [Invoice Received], [Invoice Paid], [Method Of Payment], [Date Item Received], [Quote Attatchment] FROM Spares", myConnection)

        'create a new dataset 
        Dim ds As DataSet = New DataSet
        'fill DataSet

        Try
            da.Fill(ds, "Spares")
        Catch ex As Exception
            MsgBox("Sorry, An Error Occurred" & vbNewLine & _
                   "Database contents could not be loaded" & vbNewLine & vbNewLine & _
                   "Error Message: " & ex.Message, MsgBoxStyle.OkOnly, "Could Not Load Database Information")
            Exit Sub
        End Try


        Main.DataGridView1.DataSource = ds.Tables(0)

        Main.DataGridView1.AllowUserToAddRows = False

        'Set Site Listbox

        Dim SiteString = My.Settings.SETTINGS_SiteNames
        Dim SiteBox = Main.VIEW_Site.Items

        SiteBox.Clear()

        Do Until SiteString = ""
            Dim ActiveSiteName = Left(SiteString, InStr(SiteString, "¦"))
            ActiveSiteName = ActiveSiteName.Remove(ActiveSiteName.Length - 1)

            With SiteBox
                .Add(ActiveSiteName)
            End With

            SiteString = Replace(SiteString, ActiveSiteName + "¦", "")

        Loop


        'Set DataBindings
        Main.VIEW_Ref.DataBindings.Clear()
        Main.VIEW_Ref.DataBindings.Add(New Binding("Text", ds, "Spares.ID", False, DataSourceUpdateMode.Never))

        Main.VIEW_NameOfPerson.DataBindings.Clear()
        Main.VIEW_NameOfPerson.DataBindings.Add(New Binding("Text", ds, "Spares.Name Of Person", False, DataSourceUpdateMode.Never))

        Main.VIEW_SAPJobNo.DataBindings.Clear()
        Main.VIEW_SAPJobNo.DataBindings.Add(New Binding("Text", ds, "Spares.SAP Job Number", False, DataSourceUpdateMode.Never))

        Main.VIEW_Site.DataBindings.Clear()
        Main.VIEW_Site.DataBindings.Add(New Binding("Text", ds, "Spares.Site Name", False, DataSourceUpdateMode.Never))

        Main.VIEW_AssetDesc.DataBindings.Clear()
        Main.VIEW_AssetDesc.DataBindings.Add(New Binding("Text", ds, "Spares.Asset Description", False, DataSourceUpdateMode.Never))

        Main.VIEW_SparesSupplier.DataBindings.Clear()
        Main.VIEW_SparesSupplier.DataBindings.Add(New Binding("Text", ds, "Spares.Spares Supplier", False, DataSourceUpdateMode.Never))

        Main.VIEW_SupplierContactName.DataBindings.Clear()
        Main.VIEW_SupplierContactName.DataBindings.Add(New Binding("Text", ds, "Spares.Supplier Contact Name", False, DataSourceUpdateMode.Never))

        Main.VIEW_SupplierContactNumber.DataBindings.Clear()
        Main.VIEW_SupplierContactNumber.DataBindings.Add(New Binding("Text", ds, "Spares.Supplier Contact Phone Number", False, DataSourceUpdateMode.Never))

        Main.VIEW_SupplierContactNumber.DataBindings.Clear()
        Main.VIEW_SupplierContactNumber.DataBindings.Add(New Binding("Text", ds, "Spares.Supplier Contact Phone Number", False, DataSourceUpdateMode.Never))

        Main.VIEW_SupplierContactEmail.DataBindings.Clear()
        Main.VIEW_SupplierContactEmail.DataBindings.Add(New Binding("Text", ds, "Spares.Supplier Contact Email", False, DataSourceUpdateMode.Never))

        Main.VIEW_SparesDesc.DataBindings.Clear()
        Main.VIEW_SparesDesc.DataBindings.Add(New Binding("Text", ds, "Spares.Spares Description", False, DataSourceUpdateMode.Never))

        Main.VIEW_PartNumber.DataBindings.Clear()
        Main.VIEW_PartNumber.DataBindings.Add(New Binding("Text", ds, "Spares.Part Number", False, DataSourceUpdateMode.Never))

        Main.VIEW_QuantityToOrder.DataBindings.Clear()
        Main.VIEW_QuantityToOrder.DataBindings.Add(New Binding("Text", ds, "Spares.Quantity To Order", False, DataSourceUpdateMode.Never))

        Main.VIEW_CostEach.DataBindings.Clear()
        Main.VIEW_CostEach.DataBindings.Add(New Binding("Text", ds, "Spares.Cost", False, DataSourceUpdateMode.Never))

        Main.VIEW_DateRequested.DataBindings.Clear()
        Main.VIEW_DateRequested.DataBindings.Add(New Binding("Text", ds, "Spares.Request Date", False, DataSourceUpdateMode.Never))

        Main.VIEW_DateOrdered.DataBindings.Clear()
        Main.VIEW_DateOrdered.DataBindings.Add(New Binding("Text", ds, "Spares.Date Ordered", False, DataSourceUpdateMode.Never))

        Main.VIEW_OrderedBy.DataBindings.Clear()
        Main.VIEW_OrderedBy.DataBindings.Add(New Binding("Text", ds, "Spares.Ordered By", False, DataSourceUpdateMode.Never))

        Main.VIEW_InvoiceReceivedDate.DataBindings.Clear()
        Main.VIEW_InvoiceReceivedDate.DataBindings.Add(New Binding("Text", ds, "Spares.Invoice Received", False, DataSourceUpdateMode.Never))

        Main.VIEW_InvoicePaidDate.DataBindings.Clear()
        Main.VIEW_InvoicePaidDate.DataBindings.Add(New Binding("Text", ds, "Spares.Invoice Paid", False, DataSourceUpdateMode.Never))

        Main.View_MethodOfPayment.DataBindings.Clear()
        Main.View_MethodOfPayment.DataBindings.Add(New Binding("Text", ds, "Spares.Method Of Payment", False, DataSourceUpdateMode.Never))

        Main.VIEW_DateReceived.DataBindings.Clear()
        Main.VIEW_DateReceived.DataBindings.Add(New Binding("Text", ds, "Spares.Date Item Received", False, DataSourceUpdateMode.Never))

        Main.VIEW_AdditionalComments.DataBindings.Clear()
        Main.VIEW_AdditionalComments.DataBindings.Add(New Binding("Text", ds, "Spares.Comments", False, DataSourceUpdateMode.Never))

   DataGridView_Setup.BindingUpdates() 'CALL BELOW SUB HERE
        Main.VIEW_Title.Text = "View / Update Received Spares"
    End Sub

    Public Sub BindingUpdates()
        Dim curr As New DataGridViewRow
        curr = Main.DataGridView1.CurrentRow '**THIS LINE FAILS TO GET THE CURRENT ROW, HOWEVER, IF RUN WITHOUT A NEW THREAD, IT WORKS FINE??**




        Main.VIEW_Ref.Text = curr.Cells("ID").Value
        Main.VIEW_NameOfPerson.Text = curr.Cells("Name Of Person").Value
        Main.VIEW_SAPJobNo.Text = curr.Cells("SAP Job Number").Value
        Main.VIEW_Site.Text = curr.Cells("Site Name").Value
        Main.VIEW_AssetDesc.Text = curr.Cells("Asset Description").Value
        Main.VIEW_SparesSupplier.Text = curr.Cells("Spares Supplier").Value
        Main.VIEW_SupplierContactName.Text = curr.Cells("Supplier Contact Name").Value
        Main.VIEW_SupplierContactNumber.Text = curr.Cells("Supplier Contact Phone Number").Value
        Main.VIEW_SupplierContactEmail.Text = curr.Cells("Supplier Contact Email").Value
        Main.VIEW_SparesDesc.Text = curr.Cells("Spares Description").Value
        Main.VIEW_PartNumber.Text = curr.Cells("Part Number").Value
        Main.VIEW_QuantityToOrder.Text = curr.Cells("Quantity To Order").Value
        Main.VIEW_CostEach.Text = "£" + CStr(curr.Cells("Cost").Value)
        Main.VIEW_DateRequested.Text = curr.Cells("Request Date").Value


        'Handle DBNULL From now on

        If IsDBNull(curr.Cells("Date Ordered").Value) = True Or _
            IsNothing(curr.Cells("Date Ordered").Value) = True Or _
            curr.Cells("Date Ordered").Value = "" Or _
            curr.Cells("Date Ordered").Value = "Not Ordered Yet" Then

            With Main.VIEW_DateOrdered
                .Text = "Not Ordered Yet"
                .BackColor = Color.LightPink
            End With

        Else
            With Main.VIEW_DateOrdered
                .Text = curr.Cells("Date Ordered").Value
                .BackColor = Color.White
            End With

        End If

        If IsDBNull(curr.Cells("Ordered By").Value) = True Or _
            IsNothing(curr.Cells("Ordered By").Value) = True Or _
            curr.Cells("Ordered By").Value = "" Or _
            curr.Cells("Ordered By").Value = "Not Ordered Yet" Then
            With Main.VIEW_OrderedBy
                .Text = "Not Ordered Yet"
                .BackColor = Color.LightPink
            End With
        Else
            With Main.VIEW_OrderedBy
                .Text = curr.Cells("Ordered By").Value
                .BackColor = Color.White
            End With

        End If

        If IsDBNull(curr.Cells("Invoice Received").Value) = True Or _
            IsNothing(curr.Cells("Invoice Received").Value) = True Or _
            curr.Cells("Invoice Received").Value = "" Or _
            curr.Cells("Invoice Received").Value = "No Invoice" Then
            With Main.VIEW_InvoiceReceivedDate
                .Text = "No Invoice"
                .BackColor = Color.LightPink
            End With
        Else
            With Main.VIEW_InvoiceReceivedDate
                .Text = curr.Cells("Invoice Received").Value
                .BackColor = Color.White
            End With

        End If

        If IsDBNull(curr.Cells("Invoice Paid").Value) = True Or _
            IsNothing(curr.Cells("Invoice Paid").Value) = True Or _
            curr.Cells("Invoice Paid").Value = "" Or _
            curr.Cells("Invoice Paid").Value = "Not Paid" Then
            With Main.VIEW_InvoicePaidDate
                .Text = "Not Paid"
                .BackColor = Color.LightPink
            End With
        Else
            With Main.VIEW_InvoicePaidDate
                .Text = curr.Cells("Invoice Paid").Value
                .BackColor = Color.White
            End With

        End If

        If IsDBNull(curr.Cells("Method Of Payment").Value) = True Or _
            IsNothing(curr.Cells("Method Of Payment").Value) = True Or _
            curr.Cells("Method Of Payment").Value = "" Or _
            curr.Cells("Method Of Payment").Value = "Not Paid" Then
            With Main.View_MethodOfPayment
                .Text = "Not Paid"
                .BackColor = Color.LightPink
            End With
        Else
            With Main.View_MethodOfPayment
                .Text = curr.Cells("Method Of Payment").Value
                .BackColor = Color.White
            End With

        End If
        If IsDBNull(curr.Cells("Date Item Received").Value) = True Or _
            IsNothing(curr.Cells("Date Item Received").Value) = True Or _
            curr.Cells("Date Item Received").Value = "" Or _
            curr.Cells("Date Item Received").Value = "Not Received" Then
            With Main.VIEW_DateReceived
                .Text = "Not Received"
                .BackColor = Color.LightPink
            End With
        Else
            With Main.VIEW_DateReceived
                .Text = curr.Cells("Date Item Received").Value
                .BackColor = Color.White
            End With

        End If

        If IsDBNull(curr.Cells("Comments").Value) = True Or _
            IsNothing(curr.Cells("Comments").Value) = True Or _
            curr.Cells("Comments").Value = "" Or _
            curr.Cells("Comments").Value = "No Comments Added" Then
            With Main.VIEW_AdditionalComments
                .Text = "No Comments Added"
                '.BackColor = Color.LightPink
            End With
        Else
            With Main.VIEW_AdditionalComments
                .Text = curr.Cells("Comments").Value
                '.BackColor = Color.White
            End With

        End If



    End Sub

End Module

As stated in the code above, the error appears to be that the new thread can't access information from the form?

Thanks.

Answer 1

You need to run the Connecting Sub-Routine as a new Thread. A common Example for Thread would be this:

First create your new thread:

Public t1 As Threading.Thread

Now make a call from your function to the thread

Private Sub Initialise_View()
    'Run your connecting Sub-Routine
    t1 = New Thread(New ThreadStart(AddressOf Set_Datasource))
    t1.Start()
End sub

Now your connecting Sub-Routine

Sub Set_Datasource()
    'Your code here
End sub 

Now your App won´t hang up.

At the same time you could start a Timer, let it after 30 Seconds, close the connection, now the Thread and then display your Error.

Answer 2

I need to run a background worker, or run it in another thread, but this is beyond my understanding at the moment.

Actually, the BackgroundWorkers are really straight forward, once you get the concept right. They are really just a second thread, wrapped into a out-of-the-box optimized class, already containing the methods that you need to accomplish your task without freezing your main thread.

A simple implementation, that I've used many times, would look like this:

Imports System.ComponentModel

Public Class BGWexample
    Sub MainProgram()
        '   delcare your bgWoker-object
        Dim BgWorker As BackgroundWorker

        '   initialization and basic setup of your bgWorker
        BgWorker = New BackgroundWorker()
        BgWorker.WorkerReportsProgress = False
        BgWorker.WorkerSupportsCancellation = False

        '   tell the bgWorker where it will find the code for it's already implemented methods
        AddHandler BgWorker.DoWork, AddressOf BgWorkerDoesHisThing
        AddHandler BgWorker.RunWorkerCompleted, AddressOf BgWorkerHasFinished

        '   to start your background thread, just execute the bgWoker by calling its .RunWorkerAsync-method instead of calling your already implemented method to load your data from the database
        BgWorker.RunWorkerAsync()
    End Sub

    Private Sub BgWorkerDoesHisThing(ByVal sender As Object, ByVal e As DoWorkEventArgs)
        '   this will host the code to load the data from the database, e.g. declaration of your Data-Access-Object, querying, populating DataTables etc.
    End Sub

    Private Sub BgWorkerHasFinished(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs)
        '   use this method to hide any loading screens, enable some controls etc.
    End Sub
End Class

Just put the code of your Set_Datasource(mode As Integer) inside the BgWorkerDoesHisThing()-method, and execute the BgWorker.RunWorkerAsync() method instead of your Set_Datasource(mode As Integer)-method.

This will cause the BgWorker to execute the BgWorkerDoesHisThing()-Sub, that has been attached to the .DoWork-Event by adding the according Handler in the declaration block.

Please Note: Using background threads gets a bit itchy if it comes to interaction with the GUI from the background thread.

In this example, the BgWorkerDoesHisThing()-Sub is executed in as a different thread, that is not allowed to modify the GUI-controls of the main thread, while the BgWorkerHasFinished()-Sub will be executed within the main thread again, which means, it has full access to the GUI-controls again.

So for now, I would recommend to put your GUI into a loading screen, and hide that loading screen in the BgWorkerHasFinished()-method.

And keep in mind that you might run into a Race Hazard, if your main thread is depending on the result of your background thread, but not waiting for it to finish its work. This is what the BackgroundWorker.RunWorkerCompleted-event is for, and this is the reason I added an EventHandler to this event, that will execute the dedicated BgWorkerHasFinished()-method as soon as the BgWorker finished its work.