How to bind SelectedItem property of SfComboBox to another property ?

public class State
{
      private string shortName;
      private string longName;
 
      public State(string LongName, string ShortName)
      {
          this.longName = LongName;
          this.shortName = ShortName;
      }
 
      public string ShortName
      {
          get { return shortName; }
      }
 
      public string LongName
      {
          get { return longName; }
      }
}

public class ViewModel
{
     private List<State> items;
 
     public List<State> Items
     {
           get { return items; }
           set { items = value; }
     }
 
     private object selected;
 
     public object Selected
     {
           get { return selected; }
           set { selected = value; }
      }
 
     public ViewModel()
     {
           Items = new List<State>();
           Items.Add(new State("Alaska", "AK"));
           Items.Add(new State("Arizona", "AZ"));
           Items.Add(new State("Colorado", "CO"));
           Items.Add(new State("Ontario", "ON"));
           Items.Add(new State("BritishColumbia", "BC"));
 
            Selected = Items[3];
     }
}

public partial class Form1 : Form
{
      public Form1()
      {
            InitializeComponent();
 
            ViewModel viewModel = new ViewModel();
 
            sfComboBox1.DataSource = viewModel.Items;
            sfComboBox1.DisplayMember = "LongName";
            sfComboBox1.ValueMember = "ShortName";
 
            sfComboBox1.DataBindings.Add(new Binding("SelectedItem", viewModel,"Selected",true, DataSourceUpdateMode.OnPropertyChanged));
 
      }
}