将组合框绑定到 ViewModelMain 方法

我有一个组合框，当用户从 ViewModelMain 类的变量中存储的数据中选择它时，我需要填充它，但无法让它工作。

我的ViewModel看起来像这样，GetMessagesTypes((方法是我感兴趣的方法。messageType 变量返回我需要绑定到组合框的消息类型列表。

任何指示将不胜感激。

  namespace Toolbox.ViewModel
{
    [ImplementPropertyChanged]
    internal class ViewModelMain
    {
        #region Fields
        private readonly IActionLogRepository m_ActionLogRepository;
        #endregion
        #region Properties
        public DateTime QueryFromDate { get; set; }
        public DateTime QueryToDate { get; set; }
        public int TopXRecords { get; set; }
        public ICommand SearchTopXRecord { get; private set; }
        public ICommand GetListOfmessageTypes { get; set; }
        public ICommand SearchDateCommand { get; private set; }
        public object SelectedMessageBody { get; set; }
        public ObservableCollection<IActionLog> Messages { get; set; }
        #endregion
        #region Constructor
        //Should use injection container
        public ViewModelMain(IActionLogRepository actionLogRepository)
        {
            QueryToDate = DateTime.Now;
            QueryFromDate = DateTime.Now.Subtract(TimeSpan.FromDays(1));
            m_ActionLogRepository = actionLogRepository;
            Messages = new ObservableCollection<IActionLog>();
            SearchDateCommand = new SimpleCommand { ExecuteDelegate = SetActionLogsBetweenDates };
            SearchTopXRecord = new SimpleCommand { ExecuteDelegate = SetActionLogsForTopXRecords };
            SetActionLogs();
            //GetMessagesTypes();
        }
        #endregion
        #region Methods
        private void SetActionLogs()
        {
            List<IActionLog> actionLogs = m_ActionLogRepository.GetAllActionLogs();
            Messages.Clear();
            actionLogs.ForEach(actionLog => Messages.Add(actionLog));
        }
        public void SetActionLogsBetweenDates()
        {
            List<IActionLog> actionLogs = m_ActionLogRepository.GetAllActionLogsBetweenDates(QueryFromDate, QueryToDate);
            Messages.Clear();
            actionLogs.ForEach(actionLog => Messages.Add(actionLog));
        }
        public void SetActionLogsForTopXRecords()
         {
             List<IActionLog> actionLogs = m_ActionLogRepository.GetAllTopXActionLogs(TopXRecords);
            Messages.Clear();
            actionLogs.ForEach(actionLog => Messages.Add(actionLog));
        }
        public string GetMessagesTypes()
        {
            List<IActionLog> actionLogMessageType = m_ActionLogRepository.GetAllActionLogs();
            var messageType = (
                from messageTypes in actionLogMessageType
                select messageTypes.MessageType).Distinct();
            return messageType.ToString(); //Return Messages types
        }
        #endregion
    }
}

private YourDataType selectedItem = new YourDataType();
public YourDataType SelectedItem
{
    get { return selectedItem; }
    set 
    {
        selectedItem = value; 
        NotifyPropertyChanged("SelectedItem"); 
        DoSomethingWithSelectedItem(SelectedItem); // <-- Call method here
    }
}