Wierd combo box error

[ehelin]

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

[snarfblam]

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.).

[ehelin]

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-framework-winforms-databinding/silly-outofmemoryexception-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,"

========================
  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

========================

 '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

========================

Edited July 11, 2006 by PlausiblyDamp

[ehelin]

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

[PlausiblyDamp]

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.

[ehelin]

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

 

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.