Comments by BHort (Top 31 by date)

Can I have multiple Catch ex As statements? The first being this and then the next being the more general one?

The final piece of the puzzle was two minor adjustments.

First, turn HideSelection to false on the TreeView. Simple but important.

Second, give the TreeView focus.

Doing those two things gives the nice blue background on the selected item just as if the user had clicked on it.

By the way ... the syntax for VB.Net is virtually identical so your code snippet was helpful.

Unfortunately the DB structure wont help because the TV changes depending on UI selections which determine which features and elements to display.

That said, the DB structure is roughly as follows. It has 4 different tables. Timers -> Timers/Tag Groups XRef -> Tag Groups -> Tags

Tag Groups can show up under multiple timers, hence the XRef.

Ok, I'm slowly figuring this out ... I think! ;-)

When I try and do a find, it's only looking in my 5 root nodes, not the sub-nodes. How do I get Find to also look in the sub-nodes?

Right now I'm getting a "Sequence contains no elements" error when I search for a sub-node that I know is there using text that is identical to the displayed text of the sub-node. (Actually it's a sub-sub-node but still)

In doing further development I've discovered that the multimedia timer is pretty accurate. It stays within a few microseconds of accurate without needing any help. When it does drift slightly ... if it's going too fast, I quickly stop and start it again ... and that seems to pull it back on track and/or keep it from straying too far. I do this whenever the timer is > 3 microseconds off. If it's going too slowly I haven't found a great solution other than to add in a "fake" extra tick (equal to 1/100th of a second for my application). I only do this when the error is > 8 microseconds because the impact is bigger but the result is that the timer is staying very true over an extended period with these correction measures.

It's too complex for our users. We need something *simple* for them to be able to export their data and/or import into another instance on another machine.

Could you perhaps provide an example of how I would write the code to create a proceedure "CountRecs" with the code "SELECT count(*) As numrecs FROM mytable" (trivial I know but it's simple enough to show me how it would be written which is what I'm looking for).

Understood. The DBA isn't the issue in this case ... it's more, I wouldn't know how to write it to be generated externally and I wouldn't know how to trap any errors that might get generated (although I guess a try except would hopefully be sufficient)

Totally what I needed. I didn't think it would be but it's exactly the solution. For other peoples benefit, I'm going to post it as a solution ... although you should really get the credit.

Well, what about using an ODBC connection to the DBF files? Using the Access ODBC driver to connect to the DBF database you should be able to again simply access the DBF file using SQL and ignore the fact that it's a DBF file. It wont be fast because you typically wouldn't have any indexes loaded but it would work.

Implemented the change plus added the command to reduce the priority of my DB save routine thread from RealTime to Normal priority (I previously had the entire app at Real Time priority) ... my application is keeping to within 3/1000ths of a second accuracy ... oh am I happy!

Thank you. Things are much more stable now.

But wouldn't that create a lot of overhead creating a new connection to the database for each thread?

Got it.

The correct If should be:
If allowedChars.IndexOf(e.KeyChar) = -1 And e.KeyChar <> Convert.ToChar(Keys.Back) Then

So the complete solution is to paste:

Dim allowedChars As String = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_"

If allowedChars.IndexOf(e.KeyChar) = -1 AND e.KeyChar <> Convert.ToChar(Keys.Back) Then
' Invalid Character
e.Handled = True
End If

Into the KeyPress event of a text box.

Hope this helps someone else. I really like it because it means my input testing is done up front.

Just did ... no joy. I thought it was because it would skip the back with the logic you supplied but putting NOT around the 2nd half didn't help ... but I think you might be on the right track ... I'll keep trying ...

I'm trying to implement a time correction algorithm to ensure my application timer stays closer to the original intended time. Basically to remove or at least adjust for the drift as it happens.

Is it possible to create (in the designer) an array of radio buttons?

I stand corrected. I figure I'm surviving ... so I'm not really worried about it but I do appreciate people who are willing to contribute a constructive criticism once in a while. Thanks again.

Excellent. Thank you for that. I've been programming for 30 years but I'm still fairly new to VB.Net

Asked another way ... how can I ensure the outputed number of "1"s and "2"s is what I expect if the problem is in the process scheduler?

But I'm not getting the output expected ... so how is my code working fine? I need to know that when I output for Timer 1 ... I'm going to get Timer 1 information. I don't care about the order but I do care about being confident that I'm getting the right timer.

Here is the code for my example (with a line commented out towards the bottom so you can easily switch from subroutine to task and back)

<pre>
Imports System.Threading.Tasks

Public Class Form1
Public TickCounts As Integer = 0
Public AllowTimerTics As Boolean = False
Public CurTimers(4) As TimerListDef

Public Class TimerListDef
Public TimerID As Integer
Public TimerInterval As Integer
Public CountDown As Integer
End Class

Delegate Sub myInvokedMethod(ByVal test As String) 'We need a delegate in order to be able to invoke it at runtime with a parameter

Private Sub AddErrItem(ByVal ErrStr As String)
Dim item1 As New ListViewItem
Dim tempStr As String
tempStr = Format(Now, "hh:::mm:::ss:::fff ") + ErrStr
item1 = New ListViewItem(tempStr)
lstErrors.Items.Add(item1)
End Sub

Delegate Sub myInvokedOPCMethod(ByVal test As Integer) 'We need a delegate in order to be able to invoke it at runtime with a parameter

Private Sub ReadOPCData(ByVal CurTimerToRead As Integer)
Dim DispText As String
DispText = "Timer: " & CurTimerToRead.ToString
If Me.InvokeRequired Then
Me.Invoke(System.Delegate.CreateDelegate(GetType(myInvokedMethod), Me, "AddErrItem"), New Object() {DispText})
Else
AddErrItem(DispText)
End If
End Sub

Private Sub TimerTicToc_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TimerTicToc.Tick
Dim TimerToRead As Integer

TextBox2.Text = TickCounts.ToString
If AllowTimerTics Then 'Should not allow timer tics when the Timers/Tags global variables are being recreated
For Counter = 1 To 3
CurTimers(Counter).CountDown = CurTimers(Counter).CountDown - 1
If CurTimers(Counter).CountDown <= 0 Then
CurTimers(Counter).CountDown = CurTimers(Counter).TimerInterval
TimerToRead = Counter 'We do this because the debugger warned of unexpected results of we passed the counter directly
'Launch a task to do the read to keep the time for this loop short
Task.Factory.StartNew(Sub() ReadOPCData(TimerToRead), TaskCreationOptions.AttachedToParent)
'ReadOPCData(TimerToRead)
End If
Next
TickCounts += 1
If TickCounts > 120 Then
AllowTimerTics = False
TimerTicToc.Stop()
End If
End If
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
TickCounts = CInt(TextBox1.Text)
If TimerTicToc.IsRunning Then
MessageBox.Show("Hey, it's running!")
Else
For Counter As Integer = 1 To 3
CurTimers(Counter) = New TimerListDef
CurTimers(Counter).TimerID = Counter
Next
CurTimers(1).TimerInterval = 10
CurTimers(2).TimerInterval = 25
CurTimers(3).TimerInterval = 100
CurTimers(1).CountDown = 10
CurTimers(2).CountDown = 25
CurTimers(3).CountDown = 100
Process.GetCurrentProcess().PriorityClass = ProcessPriorityClass.RealTime
AllowTimerTics = True
Try
TimerTicToc.Start()
Catch ex As Exception
MsgBox("Can't start the timer" & vbCrLf & ex.Message)
End Try
TimerTicToc.Start()
AllowTimerTics = True
End If
End Sub
End Class
</pre>

This particular example requires a ListView box, 2 text boxes and a button. The listview is for output and I've syncronized the timer to Form1 to simplify output ... although I don't intend to in the final version.

No, the counts aren't different in the total number of counts, just in the values that should be displayed.
I've got a very small project that I've created to demonstrate the problem ... but it requires the multimedia timer DLL that was part of the article here:

The Multimedia Timer for the .NET Framework

Part of my concern is coming from the fact that I'm using a component that uses a multimedia timer to implement a timer component that can generate "tics" with a frequency lower than every 15 ms. It seems to work great when I use it and call my routine as a subroutine but not when I call it as a task ... and I'm wondering if the transfer of the variable into the task is getting interrupted by another "tic" and hence the variable gets changed mid process.
Is there a way to ensure the launching of the thread is atomic? Another thought I had was to put my values into an ArrayList using a Monitor.Enter/Exit pair and pulling them off again within the task. I might not guarantee that execution 1 gets value 1 (because of the non determinism) but I can ensure that for n values there will be n calls and thus all the values will be processed.
Does that sound like a plausible option? Again, I'm fairly new at VB.Net multithreading so I'm open to being told I'm out to lunch ...

I understand the non-deterministic nature of threads but the issue that's causing me to question that being the source of the problem is the fact that the total number of "1"s and "2"s aren't correct. If you notice in my "correct" output I have 5 "1"s and 2 "2"s ... the incorrect showing 4 and 3 respectively. The quantity of each output isn't correct ... which is where my feeling like the variable is getting changed is coming from.

When I run it as a subroutine I get:

Timer: 1
Timer: 1
Timer: 1
Timer: 2
Timer: 1
Timer: 1
Timer: 2
etc.

which is correct. When I run it as a task I get:

Timer: 1
Timer: 1
Timer: 1
Timer: 2
Timer: 2
Timer: 2
Timer: 1
etc.

Or various other similar wrong values for what should be displayed.

Timer 1 is going 100 times per second. Timer 2 is 40 times per second. Timer 3 is every 1/10th of a second (not that I've shown the third timer in my sample)