How to search using multiple field USING MVC

Question

Problem

I need to search by ClassID,SectionID,InstructorID DROPDOWNLISTS and i can have options if one drop down have null value or not

search i need is (classID =NULL OR NOT)AND (sectionid =null or not)AND(InstructorID=Null or not)

I only can search by one drop down menu InstructorID BUT SECTIONID,ClassID Dropdown how to do that .

I have Model schedules as following :

public class Schedule
    {
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        [Key, Column(Order = 0)]
        public int SchedualeID { get; set; }
       // [Key, Column(Order = 1)]
        public int CourseID { get; set; }
        // [Key, Column(Order = 2)]
        [DisplayName("InstructorName")]
        public int InstructorID { get; set; }

        public int SectionID { get; set; }

        public int ClassID { get; set; }

        public int DayNum { get; set; }

        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString =
     "{0:dd-MM-yyyy}",
      ApplyFormatInEditMode = true)]
        [Required]
        public DateTime? FromDate { get; set; }
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString =
    "{0:dd-MM-yyyy}",
     ApplyFormatInEditMode = true)]
        [Required]
        public DateTime? ToDate { get; set; }

        [ForeignKey("ClassID")]
        public virtual Class classes { get; set; }
        [ForeignKey("SectionID")]
        public virtual Section section { get; set; }
        [ForeignKey("DayNum")]
        public virtual Calender calender { get; set; }
        public virtual Instructor instructores { get; set; }
        public virtual Courses courses { get; set; }
    }
}

 

This schedule model have foreign key for more tables as Class,Section,Instructor,Calender

All these tables have relations with table schedule

I need to get data from schedule based on ClassID,SectionID,InstructorID DROPDOWNLISTS

But i cannot do search by multiple fields

I only can search by InstructorID FIELD

What I try

Index action inside schedule controller

code below working but only InstructorID Drop down not all drop down

public ActionResult Index()
        {
            ViewBag.InstructorID = new SelectList(db.Instructors, "InstructorID", "InstructorName");
            var schedule = db.schedule.Include(s => s.calender).Include(s => s.classes).Include(s => s.courses).Include(s => s.instructores).Include(s => s.section);

            return View(schedule.ToList());
        }
        [HttpPost]
        public ActionResult Index(int InstructorID)
        {
            ViewBag.InstructorID = new SelectList(db.Instructors, "InstructorID", "InstructorName");
            var schedule = db.schedule.Include(s => s.calender).Include(s => s.classes).Include(s => s.courses).Include(s => s.instructores).Include(s => s.section).Where(s=>s.InstructorID==InstructorID);

            return View(schedule.ToList());
        }

In view of Index action in schedule controller

<p>
    @Html.ActionLink("Create New", "Create")
    @using (Html.BeginForm())
    {
        <p>
            Title:@Html.DropDownList("InstructorID", null, htmlAttributes: new { @class = "form-control" })<br />
            <input type="submit" value="Filter" />
       </p>
    }
</p>