Create a right triangle with loop in Visual Basic - vb.net

Question

I tried to solve the Visual Basic assignment in dart and I was able to using this :
I don't know if that's the best way to do it though. In Visual Studio I don't know what commands or methods that can help me do this and this is the result there.
Public Class Form1
Dim input As Integer
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Me.Text = "Nested Loops"
End Sub
Private Sub Label1_Click(sender As Object, e As EventArgs) Handles Label.Click
End Sub
Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles InputTextBox.TextChanged
input = Val(InputTextBox.Text)
End Sub
Private Sub ComputeButton_Click(sender As Object, e As EventArgs) Handles ComputeButton.Click
For outer As Integer = 1 To input
For inner As Integer = 1 To outer
ListBox.Items.Add("#")
Next
ListBox.Items.Add("")
Next
End Sub
Private Sub ListBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListBox.SelectedIndexChanged
End Sub
End Class
I get this error when trying to treat it like dart
System.InvalidCastException: 'Conversion from string "#" to type 'Double' is not valid.'
I need help.

Answer 1

Consider:
For outer As Integer = 1 To input
Dim s as String
For inner As Integer = 1 To outer
s &= "#"
Next
ListBox.Items.Add(s)
Next
i.e. you want to have a string that grows by one # each time before you add it to the thing that will display it:
"#"
"##"
"###"
"####"
This uses simple string concatenation. In the future when you're programming for real (and e.g. wanting to run a process that creates millions of strings) you should consider using something designed for the job, such as a StringBuilder. This will be ok for some small handful of operations though
Though I'm rather puzzled why you use a listbox and not just a textbox..