Randomize Lines order in textbox with StringBuilder

I'm trying to randomize the final Result here the idea is get the textbox lines do some code , then export it to textbox2 , the code is working but i want to randomize the lines order when exporting to textbox2

        Dim newr As New StringBuilder
           For Each line In texbox1.text.Lines
           newr.AppendLine(line & " CODE-DONE-1")
           newr.AppendLine(line & " CODE-DONE-2")
           newr.AppendLine(line & " CODE-DONE-3")

        Next
    textbox2.text = newr.ToString 'Want to randomize Lines Order

Example if i put in textbox1

1
2
3

i want the output in textbox2

3 Code-Done-1
1 Code-Done-3
2 Code-Done-2
3 Code-Done-3
1 Code-Done-1
3 Code-Done-2
2 Code-Done-3

Solution

Create a class level variable of Random type:

Imports System.Linq
'//

Private ReadOnly rand As New Random
'//

Using the StringBuilder with For..Loop way:

Dim sb As New StringBuilder

For Each line In TextBox1.Lines.
    Where(Function(x) Not String.IsNullOrWhiteSpace(x)).
    OrderBy(Function(x) rand.Next)
    sb.AppendLine($"{line} Code-Done")
Next

TextBox2.Text = sb.ToString

The OrderBy(Function(x) rand.Next) part will shuffle the lines of the first text box and display them in the second one..

Alternatively, you can use the extension methods to achieve that in just one line:

TextBox2.Lines = TextBox1.Lines.
    Where(Function(x) Not String.IsNullOrWhiteSpace(x)).
    OrderBy(Function(x) rand.Next).
    Select(Function(x) $"{x} Code-Done").ToArray

So choose the appropriate way for you.

According to your edit, if you want to append the outputs, replace the StringBuilder with a class level variable of List(Of String) type and edit the code as follows:

Imports System.Linq
'//

Private ReadOnly rand As New Random
Private ReadOnly output As New List(Of String)

'//

For Each line In TextBox1.Lines.
    Where(Function(x) Not String.IsNullOrWhiteSpace(x))
    output.Add($"{line} Code-Done")
Next

TextBox2.Lines = output.OrderBy(Function(x) rand.Next).ToArray