Question

I’m using visual studios 2008, VB9 and I am trying to write an app that basically performs calculations on a set of data input by a user. During the calculations, I want to display the data at each step, and have it retained in the display area on the GUI (not overwritten by the next data being displayed).

For example:

UserInput = 1

Do

  UserInput += 1

  OutputLabel.Text = "UserInput " & UserInput

Loop Until UserInput = 5

and the output would look like

UserInput 1
UserInput 2
UserInput 3
UserInput 4
UserInput 5

I tried this, and other loop structures and can’t seem to get things right. The actual app is a bit more sophisticated, but the example serves well for logical purposes.

Any tips are welcome, thanks!

Answer 1

This is the simple version:

Dim delimiter as String = ""
For UserInput As Integer = 1 To 5
    OutputLabel.Text &= String.Format("{0}UserInput {1}", delimiter, UserInput)
    delimiter = " "
Next

However, there are two problems with it and others like it (including every other answer given so far):

1. It creates a lot of extra strings
2. Since it’s in a loop the label won’t be able to process any paint events to update itself until you finish all of your processing.

So you may as well just do this:

Dim sb As New StringBuilder()
Dim delimiter As String = ""
For UserInput As Integer = 1 To 5
    sb.AppendFormat("{0}UserInput {1}", delimiter, UserInput)
    delimiter = " "
Next
OutputLabel.Text = sb.ToString()

And if you really want to have fun you can just do something like this (no loop required!):

OutputLabel.Text = Enumerable.Range(1, 5).Aggregate(Of String)("", Function(s, i) s & String.Format("UserInput {0} ", i))