Recursive string creation

[barrykellett]

Hi, I have the following simple piece of code:

For Each Item In ListBox1.Items
If Item.Selected Then
Stuff = Stuff & "," & Item.Text
End If

Next

This Will create me a String of email addresses seperated by "," however as it is now i get a "," before the first address which i dont want. How can i get round this? I am sure it is very logical but I cant think how!!
Thanks

 

[adonet]

try this:
stuff = Item.Text
Stuff = Stuff & "," & Item.Text

 

[barrykellett]

I had tried this, but if i place both lines inside the loop it produces addresses twice

 

[adonet]

try add vbcrl or vbnewline

 

[cappmgr]

when your for is done
For
...
Next
Stuff = Stuff.Remove(0, 1)
hth,
Marty

 

[barrykellett]

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Line 34:
Line 35: Next
Line 36: Stuff = Stuff.Remove(0,1)
Line 37: If Stuff <> "" Then
Line 38: Label1.Text = "<b>You chose :</b> <br>" & Stuff

 

[stsuing]

For Each Item In ListBox1.Items
If Item.Selected Then
if stuff = string.empty then
Stuff = Item.Text
else
Stuff = Stuff & "," & Item.Text
end if
End If
Next

You should be using a System.Text.StringBuilder to do this. Use Stringbuilder.Append(). Concatenating strings is very bad practice.

 

[JohnYingling]

Better yet. Use a StringBuilder. It saves on garbage collection on all those intermediate strings.
Dim sb as New System.Text.Stringbuilder(100)
For Each Item In ListBox1.Items
If Item.Selected Then
if sb.Length > 0 then
sb.Append(",")
end if
sb.append(Item.Text)
End if
Next
Stuff = sb.tostring
' Now only sb as to "Garbage Collected"

The concatenation that you had is "murder" on storage and causes Garbage Collection of many separate string objects.
Stuff = Stuff & Item.text does not replace or immediately free the storeage for the previous contents of stuff.
Say each line is 5 characters.
5 * (10 * 10 + 10) / 2 = 275 characters allocated .

It may not seem like much but it builds up after you write all your programs like that and they all run at the same time.

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