title: Select multiple items from DropDownList into TextBox, No duplicates
body: <p>i used the following technique to Select multiple items from DropDownList into TextBox with No duplicates, however i dont think it is the most proper way, any ideas.</p>
  
  <p><img src="https://i.stack.imgur.com/E5s3R.jpg" alt="alt text"></p>
  
  <p>pressing again with same value selected</p>
  
  <p><img src="https://i.stack.imgur.com/puTyq.jpg" alt="alt text"></p>
  
  <p>choose another value from DDL and press button</p>
  
  <p><img src="https://i.stack.imgur.com/jLfx9.jpg" alt="alt text"></p>
  
  <p>here is my code</p>
  
  <pre><code>Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click
      If TextBox2.Text.Contains(DropDownList1.SelectedItem.Text) Then
          Dim m As New Label
          m.Text = "duplicate !"
          Me.form1.Controls.Add(m)
          Exit Sub
  
      End If
      If TextBox2.Text = "" Then
          TextBox2.Text = DropDownList1.SelectedItem.Text
      Else
          TextBox2.Text = TextBox2.Text + " , " + DropDownList1.SelectedItem.Text
      End If
  End Sub
  </code></pre>