how to use Inotifypropertychanged

<listboxitem foreground="Red" fontfamily="Verdana" fontsize="12" fontweight="Bold" verticalalignment="Center">
                    <checkbox name="baseMapChkBox" ischecked="{Binding IsBaseMapChecked,Mode=TwoWay}" horizontalalignment="Center" verticalalignment="Center">
                            <textblock text="Base Map Layer"></textblock>
                    </checkbox>
                </listboxitem>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Input;
using System.ComponentModel;
using Microsoft.Practices.Composite.Presentation.Commands;

namespace CoM_SWBaseMapModule
{
    public class BaseMapViewModel : ViewModelBase, INotifyPropertyChanged
    {
        #region Members
        private ICommand baseMapCheckCommand;
        private BaseMapService baseMapService;
        private bool isbaseMapChecked;
        private object x=null;
        #endregion

        #region Properties
        public BaseMapView BaseMapView { get; private set; }
        public MapService MapService { get; private set; }
       
        public  bool IsBaseMapChecked
        {

            get { return isbaseMapChecked; }
            set
            {
                isbaseMapChecked = value;
                OnBaseMapCheck(x);
                OnCheckPropertyChanged("IsChecked");
            }
        }
        #endregion


        #region Methods
        public BaseMapViewModel(BaseMapView baseMapView, MapService mapService)
        {
            BaseMapView = baseMapView;
            MapService = mapService;
            baseMapService = new BaseMapService();
            IsBaseMapChecked = true;

        }
        #endregion
        #region CommandProperties
       
        #endregion

        #region Private Methods
        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnCheckPropertyChanged(string propertyName)
        {
           if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs("IsChecked"));
        }


        private void OnBaseMapCheck(object p)
        {
            if (isbaseMapChecked)
                baseMapService.LoadBaseMap(MapService, true);
            if (!isbaseMapChecked)
                baseMapService.LoadBaseMap(MapService, false);
        }

        #endregion

    }
}