Append XML file or XML Alternative

[Tesla1886]

I am using the following code to add new data to the combobox and prevent duplicates.

        If ReceiveComboBox.Items.Count = 0 And ReceiveComboBox.Text <> "" Then
            ReceiveComboBox.Items.Add(ReceiveComboBox.Text)

        ElseIf ReceiveComboBox.Text <> "" Then
            For Each item As String In ReceiveComboBox.Items.ToString
                If item <> (ReceiveComboBox.Text) Then
                    ReceiveComboBox.Items.Add(ReceiveComboBox.Text)
                    Exit For

                End If
            Next
        End If

When I run the program and attempt to add data to the combobox I get the following error

System.ArgumentException: 'Items collection cannot be modified when the DataSource property is set.'

I have three comboboxs and using the same code for all three, The user will need to add data to the comboboxes to all three comboboxes.

What can I do to resolve this?