一、前言

      保证一个类仅有一个实例，并提供一个该实例的全局访问点。

二、代码

public class ApplicationServices
{
        public static readonly Lazy<ApplicationServices> ServicesInstance
               = new Lazy<ApplicationServices>(() => new 
               ApplicationServices()); //Lazy加载

        private ProjectSettingManager _projectManager;

        public ProjectSettingManager ProjectManager
        {
            get { return _projectManager;
        }

        public static ApplicationServices Instance
        {
            get { return ServicesInstance.Value; }
        }

        public ApplicationServices()
        {
              
        }

}