how to validate textbox from accepting duplicates and combo box from displaying dupli

[imoroyussif640]

I have a text box which will be use accept the input,
combo box for displaying the output.
Now, i some codes that will be use to prevent me from entering
repeated numbers into the text box and also i need some codes to prevent the combo box from displaying the output.thanks

[Luk3r]

Instead of asking what you've tried for such a simple request, I'm just going to provide you with something. You can modify it to your liking. I used a textbox, a button, and a combobox. I put this code on my button. I suggest you test it on a new project first.

        Dim uniqueItem As String = TextBox1.Text
        Dim uniqueItemsExists As Boolean = False

        For Each itm In ComboBox1.Items
            If itm = uniqueItem Then
                uniqueItemsExists = True
            End If
        Next

        If uniqueItemsExists = False Then
            ComboBox1.Items.Add(uniqueItem)
        End If