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vb.net remove object

Posted on 2014-09-29
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Last Modified: 2014-09-29
The below loop appears to remove the objects "MyNote" that match the criteria because they disappear from the form, but they remain due to the numbers still show up in any math performed on the collection of objects.  An example of the math is the next loop.  How can I remove the objects "MyNote" from memory in addition to removing from the form so they no longer show up in the loop that performs math on the collection?

For Each MyNote As RegisterSingleLine In col
   If MyNote.CmdHighLight.BackColor = Color.Yellow Then
   Me.SplitContainer1.Panel2.Controls.Remove(MyNote)
  End If
Next MyNote

LblTOTAL.Text = 0
For Each MyNote As RegisterSingleLine In col
   LblTOTAL.Text = CInt(LblTOTAL.Text) + CInt(MyNote.TxtPrice.Text)
Next MyNote
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Question by:dastaub
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6 Comments
 
LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 40349389
you are indeed removing it from the "form", but not from the collection, I do presume that col is not referring to Me.SplitContainer1.Panel2.Controls

you need to also remove the object from the collection, but if you do this:
For Each MyNote As RegisterSingleLine In col
   If MyNote.CmdHighLight.BackColor = Color.Yellow Then
     Me.SplitContainer1.Panel2.Controls.Remove(MyNote)
     col.Remove(MyNote)
  End If
Next MyNote

Open in new window

you will run into this error:
Collection was modified; enumeration operation may not execute.

the alternatives are :
* create another collection that holds the items to be removed, and after you first loop, loop on that collection to remove the items from the original collection
* use a FOR loop on the index positions (from last to first item using STEP -1) instead of FOR EACH
0
 
LVL 45

Expert Comment

by:AndyAinscow
ID: 40349413
Another alternative:

For Each MyNote As RegisterSingleLine In col
   If MyNote.CmdHighLight.BackColor = Color.Yellow Then
   Me.SplitContainer1.Panel2.Controls.Remove(MyNote)
  End If
Next MyNote

LblTOTAL.Text = 0
At this point you loop through the Me.SplitContainer1.Panel2.Controls collection and then perform the totals calculation on the RegisterSingleLine objects in that collection.
0
 

Author Comment

by:dastaub
ID: 40350003
below "Another Alternative", I do not see any change in the code?
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LVL 45

Expert Comment

by:AndyAinscow
ID: 40350030
Look again.

Your code : For Each MyNote As RegisterSingleLine In col  (you have some collection called col)
My suggestion:  loop through the Me.SplitContainer1.Panel2.Controls collection  (this uses the inbuilt collection of controls on the form - which you have removed the unwanted controls from)
0
 

Author Comment

by:dastaub
ID: 40350234
I'm trying to see the change, but it's not clear?

For Each MyNote As RegisterSingleLine In col
    If MyNote.CmdHighLight.BackColor = Color.Yellow Then
    Me.SplitContainer1.Panel2.Controls.Remove(MyNote)
   End If
 Next MyNote


For Each MyNote As RegisterSingleLine In col
    If MyNote.CmdHighLight.BackColor = Color.Yellow Then
    Me.SplitContainer1.Panel2.Controls.Remove(MyNote)
   End If
 Next MyNote
0
 
LVL 45

Accepted Solution

by:
AndyAinscow earned 2000 total points
ID: 40350348
I'll repeat my earlier comment:

Another alternative:

For Each MyNote As RegisterSingleLine In col
   If MyNote.CmdHighLight.BackColor = Color.Yellow Then
   Me.SplitContainer1.Panel2.Controls.Remove(MyNote)
  End If
Next MyNote

LblTOTAL.Text = 0
At this point you loop through the Me.SplitContainer1.Panel2.Controls collection and then perform the totals calculation on the RegisterSingleLine objects in that collection.
0

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