<ComboBox ItemsSource="{Binding Items}"
  DisplayMemberPath="Value"
  SelectedValuePath="Key"
  SelectedValue="{Binding SelectedItemCode}"/>

ViewModel code:

// Key = ItemCode, Value = Name
public IDictionary<string, string> Items{get; private set;}  

public string SelectedItemCode
{
 get
 {
  return Settings.Default.SelectedItemCode;
 }
 set
 {
  if (Settings.Default.SelectedItemCode != value)
  {
   Settings.Default.SelectedItemCode = value;
   OnPropertyChanged("SelectedItemCode");
  }
 }
}

A settings file is used to store the user selection. Of cause you have to save the settings e.g. if your view is closed.