using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using CMS.SettingsProvider;

namespace CMSApp.App_Code
{
    [ClassLoader]
    public partial class CMSModuleLoader
    {
        private class ClassLoader : CMSLoaderAttribute
        {
            public override void Init()
            {
                ClassHelper.OnGetCustomClass += ClassHelper_OnGetCustomClass;
            }

            private void ClassHelper_OnGetCustomClass(object sender, ClassEventArgs e)
            {
                if (e.Object == null)
                {
                    switch (e.ClassName)
                    {
                        // Gets an instance of the CustomTask class.
                        case "Custom.CustomTask":
                            e.Object = new Custom.CustomTask();
                            break;
                    }
                }
            }

        }
    }

}

App_Code > CustomTask.cs :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using CMS.EventLog;
using CMS.Scheduler;


namespace Custom
{
    public class CustomTask : ITask
    {
        /// <summary>
        /// Executes the task.
        /// </summary>
        /// <param name="ti">Info object representing the scheduled task</param>
        public string Execute(TaskInfo ti)
        {
            string detail = "Executed from '~/App_Code/CustomTask.cs'. Task data:"
                            + ti.TaskData;

            // Logs the execution of the task in the event log.
            EventLogProvider.LogInformation("CustomTask", "Execute", detail);

            return null;
        }

    }
}using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using CMS.EventLog;
using CMS.Scheduler;


namespace Custom
{
    public class CustomTask : ITask
    {
        /// <param name="ti">Info object representing the scheduled task</param>
        public string Execute(TaskInfo ti)
        {
            string detail = "Executed from '~/App_Code/CustomTask.cs'. Task data:"
                            + ti.TaskData;
            EventLogProvider.LogInformation("CustomTask", "Execute", detail);

            return null;
        }
    }
}

Task display name : MyTask
Task assembly name: : App_Code
Task class name: Custom.CustomTask.cs