Three text box all line join in list of string - vb.net

Question

I want to do is just like string join with three text box all line will be merge here's my sample
Textbox1.Text lines:
Sample1
Sample2
Sample3
Textbox2.Text lines:
: (seperator)
Textbox3 lines:
Pass1
Pass2
Pass3
Here's my code for merging all text box
For Each str As String In Me.right.Lines
For Each str2 As String In Me.sep.Text
For Each str3 As String In Me.left.Lines
If Not str2 = "" Then
'(change into list of string)
sam.Text += str + str2 + str3 & vbNewLine
Else
'(change into list of string)
sam.Text += str + str3 & vbNewLine
End If
Next
Next
Next
and I want to do my merge result will be
Dim listsample = New List(Of String)
listsample.AddRange(Strings.Split(str + st2 + st3 + " ", " ", -1, CompareMethod.Binary))
and I want final result will be
listsample.AddRamge(Strings.Split("Sample1:Pass1 Sample2:Pass2 Sample3:Pass3, " ", -1, CompareMethod.Binary))
for easy to understand what I'm saying is how can I convert this
sam.Text += str + str3 & vbNewLine
into this
listsample.AddRamge(Strings.Split("Sample1:Pass1 Sample2:Pass2 Sample3:Pass3, " ", -1, CompareMethod.Binary))

Answer 1

Private Sub OpCode()
Dim lst As New List(Of String)
Dim sep = TextBox2.Text
For Each line1 As String In TextBox1.Lines
For Each line2 As String In TextBox3.Lines
If Not sep = "" Then
lst.Add(line1 & sep & line2)
Else
lst.Add(line1 & line2 & vbNewLine)
End If
Next
Next
For Each s In lst
Debug.Print(s)
Next
End Sub