Wierd combo box error

E

ehelin

Freshman
Joined
Oct 11, 2005
Messages
48
Hi:

I am getting an out of memory exception from a combo box. I found a reference on the internet about this possibly occuring if the to string method of the objects contained in the combo box returning null. I have eliminated this possibility...and the error is still occurring.

Anyone seen this?

Eric
 
It can be a little difficult to diagnose the problem with only a very simple description of the symptoms. It would be best if you could provide some code, but you should at least give some sort of details (What are you putting in the ComboBox's collection? Does it happen every time? What do you get when you call the .ToString method? etc., etc., etc.).
 
Here are the specifics

Please bare with me...this post will be long with the error/code post. I will do the best formatting I can :)

This is what I have so far:

Reference to possible fix that I have ruled out (I think <grin!>)...this guy seemed to thing that the culprit might be the to tostring method returning a null value.

http://www.hightechtalks.com/dotnet...ception-thrown-databound-combobox-225593.html

Why do I think its ruled out? This is the error returned. The value returned by the tostring method is the pharmacy name and it has a name...in the error message, this value is "Pharm Name: COMAL DRUG,"
Code: 
========================
   Start Error Msg 
========================
Application Domain:    MAInput.exe
Assembly Codebase:     file:///C:/Program Files/TMC/MAInput/MAInput.exe
Assembly Full Name:    MAInput, Version=1.0.2343.17411, Culture=neutral, PublicKeyToken=null
Assembly Version:      1.0.2343.17411
Assembly Build Date:   6/1/2006 10:40:22 AM

Exception Source:      
Exception Type:        System.Exception
Exception Message:     Nested Catch Pharm null ptr error.  ErrLine: 4, Pharm Name: COMAL DRUG, Pharm List Name: COMAL DRUG (New Braunfels) E. North St. & E. Garza St., Pharm Db Id: 337, Orig Ex: Too many items in the combo box.
Exception Target Site: Object reference not set to an instance of an object.

========================
   End Error Msg 
========================
Offending Method - Please note that there is a lot of temporary code (i.e. ErrLine variable, nested try/catch stmts, etc.) I am using to try and track down the specific of what is happen...I don't usually wrap try catch stmts inside other try catch stmts :)

According to my tests so far, the error being thrown starts at ErrLine 4.

========================
Start Code
========================
Visual Basic: 
  'This method populates any previous visit's selected pharmacy if none is
  'selected yet.
  Private Sub PopulatePrevPharm(ByVal pPrevPharm As Pharmacy)
    Dim PharmCmboCtr As Integer
    Dim PharmMatchFd As Boolean
    Dim Ctr As Integer
    Dim ErrLine As Integer = 1      'error code
    Dim CurPharm As Pharmacy        'error code
    Dim Ex2 As Exception            'error code

    Try
      '------------------------------------------------------------------------------
      'if a pharmacy was set in the previous visit, but one doesn't exist for this one,
      'populate with the prev pharmacy and show as green.
      PharmCmboCtr = 0
      PharmMatchFd = False

      ErrLine = 2

      If Not pPrevPharm Is Nothing Then
        Try  'nested try/catch to locate bug
          'cycle through the list and see if the one we are bring in is in the list
          For Each Pharm As Pharmacy In cmboDefaultPharmacy.Items
            ErrLine = 3
            '---------------------------------------
            CurPharm = Pharm
            ErrLine = 31
            If Pharm.PharDBId = pPrevPharm.PharDBId Then
              ErrLine = 32
              cmboDefaultPharmacy.SelectedIndex = PharmCmboCtr
              ErrLine = 33
              cmboDefaultPharmacy.BackColor = Color.LightGreen
              ErrLine = 34
              PharmMatchFd = True
              Exit For
              ErrLine = 35

            End If

            PharmCmboCtr += 1

          Next

        Catch ex As Exception
          'log our elusive pharmacy null pointer exception.
          If ex.Message.IndexOf("Too many items in the combo box") <> -1 Then
            Ex2 = New Exception("1Nested Catch Pharm null ptr error.  ErrLine: " + Convert.ToString(ErrLine) _
                        + ", Pharm Name: " + CurPharm.Name + ", Pharm List Name: " _
                            + CurPharm.ListName + ", Pharm Db Id: " + Convert.ToString(CurPharm.PharDBId) _
                              + ", Orig Ex: " + ex.message)
          Else
            Ex2 = New Exception("Nested Catch Pharm non-null ptr error.  Orig Message: " + ex.message)
          End If

          LocalErrorLink.Error_Handler(Ex2)
        End Try

        ErrLine = 4

        'if not in combo box, add
        Ctr = 0

        If Not PharmMatchFd Then
          cmboDefaultPharmacy.Items.Add(pPrevPharm)

          ErrLine = 5

          Try  'nested try/catch to locate bug
            For Each pharm As Pharmacy In cmboDefaultPharmacy.Items
              ErrLine = 6
              CurPharm = Pharm

              If pharm.equals(pPrevPharm) Then
                cmboDefaultPharmacy.SelectedIndex = Ctr
                cmboDefaultPharmacy.BackColor = Color.LightGreen
              End If

              Ctr += 1
            Next

          Catch ex As Exception
            'log our elusive pharmacy null pointer exception.
            If ex.Message.IndexOf("Too many items in the combo box") <> -1 Then
              Ex2 = New Exception("2Nested Catch Pharm null ptr error.  ErrLine: " + Convert.ToString(ErrLine) _
                          + ", Pharm Name: " + CurPharm.Name + ", Pharm List Name: " _
                              + CurPharm.ListName + ", Pharm Db Id: " + Convert.ToString(CurPharm.PharDBId) _
                                + ", Orig Ex: " + ex.message)

            Else
              Ex2 = New Exception("Nested Catch Pharm non-null ptr error.  Orig Message: " + ex.message)
            End If

            LocalErrorLink.Error_Handler(Ex2)
          End Try

          ErrLine = 7

        End If
      End If

      ErrLine = 8

      cmboDefaultPharmacy.Sorted = True

    Catch ex As Exception
      'log our elusive pharmacy null pointer exception.
      If ex.Message.IndexOf("Too many items in the combo box") <> -1 Then
        Ex2 = New Exception("3Nested Catch Pharm null ptr error.  ErrLine: " + Convert.ToString(ErrLine) _
                    + ", Pharm Name: " + CurPharm.Name + ", Pharm List Name: " _
                        + CurPharm.ListName + ", Pharm Db Id: " + Convert.ToString(CurPharm.PharDBId) _
                          + ", Orig Ex: " + ex.message)
        LocalErrorLink.Error_Handler(Ex2)

        'log as normal error
      Else
        LocalErrorLink.Error_Handler(ex)
      End If

    End Try

  End Sub
========================
Start Code
========================
 
Last edited by a moderator:
Think I found culprit

Hi:

I think I found the culprit...never mix setting up your GUI with another thread...all kinds of crazy things can happen :)

If you have to, put all your GUI touching code in your thread's call back method...but the safer thing to do (anybody correct me if this is wrong) is to load your data and then populate your GUI once everything is loaded...controlling dependancies with boolean variables (i.e. test each thread to see if its loaded...something like "If ThreadComplete Then load that portion of my gui".

My boss wants us to make our loads as fast as possible, so we multithread gathering data and as it comes in, we populate our GUI. There was one remote dependancy I thought I had taken care of...oops! Seems to be fixed now :)

Thanks!

Eric
 
If you are doing work in a background thread and need to update the UI you will need to get the main thread to 'Invoke' it, the InvokeRequired property should tell you if you need to do this.

Search these forums and you should find a couple of mentions of this along with examples of the solution.
 
Thanks!

Thanks for the response!

I did a look up on the forum, and found an example of this from Wile...who helped me in an email.

Thanks for the help!

Eric

PlausiblyDamp said:
If you are doing work in a background thread and need to update the UI you will need to get the main thread to 'Invoke' it, the InvokeRequired property should tell you if you need to do this.

Search these forums and you should find a couple of mentions of this along with examples of the solution.
Click to expand...
 
Back
Top