InvalidArgument=Value of ' ' is not valid for 'index' (' ' inside number) - vb.net

Question

This is my first question. I can't solve this error for 2 weeks.
In order to solve the problem signed up.
This is my vb code.
Try
For i As Integer = 0 To ListBox1.Items.Count - 1 Step 1
For j As Integer = 0 To ListBox2.Items.Count - 1 Step 1
If ListBox1.Items(i).ToString().Equals(ListBox2.Items(j).ToString()) = True Then
ListBox1.Items.RemoveAt(i)
End If
Next
Next
Catch ex As Exception
MsgBox("LOAD ERROR: " + ex.Message, vbCritical, "ERROR")
End Try
error :
InvalidArgument=Value of '20' is not valid for 'index'(' ' is varient.)
Project has no problems except for this error

Answer 1

Try this:
Dim items = ListBox1.Items.Where(Function(item) ListBox2.Items.Contains(item)).ToList()
For Each item in items
ListBox1.Remove(item)
Next

Answer 2

When I run your code, I receive a different exception, argument out of range...and that is caused by deleting items from an indexed collection while you're iterating through it. For example, let's say listbox1 has 10 items in it. If you find item number 1 in listbox2 and delete it, now you only have 9 items left in listbox1. The problem is, when you entered your loop, you told it to loop 10 items, and it will still try to do that. At some point, if any items are deleted, this loop will throw an exception...so you will need to change that sooner or later. To mitigate this, step through the collection that you'll be deleting items from backward like this:
For i As Integer = ListBox1.Items.Count - 1 to 0 Step -1
When I run the code with the change shown above, it works as intended and removes the duplicate items from listbox1. Unfortunately, I was unable to reproduce your invalid argument exception. It's odd to see that because usually that exception likes to pop up when using listviews, not listboxes. Perhaps you can edit your post and add a screenshot of the data in your listboxes so it's easier for other people to troubleshoot.

Answer 3

As you remove items from ListBox1 the total item count will decrease (obviously), however the For loop does not respect that. A For loop will only have the right side of To set once, which is done prior to the first iteration.
What you're currently doing is actually equal to this:
Dim a As Integer = ListBox1.Items.Count - 1
For i As Integer = 0 To a Step 1
Dim b As Integer = ListBox2.Items.Count - 1
For j As Integer = 0 To b Step 1
...
Next
Next
The fix for this is simple; create a variable that holds how many items you have removed, then, in an If-statement, check if i is more or equal to the current item count subtracted with how many item's you've removed. If so, exit the loop.
Dim ItemsRemoved As Integer = 0
For i As Integer = 0 To ListBox1.Items.Count - 1 Step 1
If i >= ListBox1.Items.Count - ItemsRemoved Then Exit For
For j As Integer = 0 To ListBox2.Items.Count - 1 Step 1
If ListBox1.Items(i).ToString().Equals(ListBox2.Items(j).ToString()) = True Then
ListBox1.Items.RemoveAt(i)
End If
Next
Next
For future reference you should also always remove/comment out the Try/Catch-statement so you can see where the error occurs and get more detail about it.

Answer 4

The point of my answer is that when you iterating any collection, you should NOT try to modify this collection. In for-loops you run into such trouble. But you can iterate using while-loop with no issues
Try
Dim index As Integer = 0
While index < ListBox1.Items.Count '!! this code based on fact that ListBox1 item Count changes
For j As Integer = 0 To ListBox2.Items.Count - 1 ' <- this is ok because ListBox2 doesn't chage
If string.Equals(ListBox1.Items(index).ToString(), ListBox2.Items(j).ToString()) Then
ListBox1.Items.RemoveAt(index)
Continue While ' no index increase here because if you remove item N, next item become item N
End If
Next
index += 1
End While
Catch ex As Exception
MsgBox("LOAD ERROR: " + ex.Message, vbCritical, "ERROR")
End Try
This is good example of how things actually work. And it shows few techniques

Answer 5

I just selected Build-->Clean solution and it cleaned out the bad elements. This occurred as a result of adding and deleting menu items, without deleting the subroutines of the deleted menu items. As soon as I cleaned the solution, and then ran the project, the error was gone.