MVC 4 Changing multiple display fields based on DropDownListFor selection

Question

MVC 4 Changing a field based on DropDownListFor selection

First off, almost the same as the above question, but the solution isn\'t working for this one.

I have

Answer 1

One thing you are doing is not returning a single result from your FillCourseInfo action.

This means your json result is a list of StudentCourseDetails. You would have to use $('#Dates').val(data[0].courseDates); to get your values.

Or if you're just expecting a single value you can use .FirstOrDefault() at the end of your linq query.

var ret = (from e in db.Enrollments 
               join c in db.Courses on e.CourseID equals c.CourseID
               where e.StudentID == StudentID && e.CourseID == CourseID
               select new StudentCourseDetails
               {
                   courseDates = c.CourseStartDate.ToString() + " " + c.CourseEndDate.ToString(),
                   projectName = e.Project.ProjectTitle,
                   graduated = e.Graduated

               }).FirstOrDefault();

I created another .NET Fiddle for you. DotNetFiddle

To use ToString in your linq query, convert the result to a list, then build your json

 var ret = (from e in db.Enrollments
                   join c in db.Courses on e.CourseID equals c.CourseID
                   where e.StudentID == StudentID && e.CourseID == CourseID
                   select new
                   {
                       courseStartDate = c.CourseStartDate,
                       courseEndDate = c.CourseEndDate,
                       projectName = e.Project.ProjectTitle,
                       graduated = e.Graduated

                   }).ToList()
                   .Select(a => new StudentCourseDetails() {
                       courseDates = a.courseStartDate.ToString() + " " + a.courseEndDate.ToString(),
                       projectName = a.projectName,
                       graduated = a.graduated
                   }).FirstOrDefault();

Answer 2

Change your Javascript function with below fuction:

$("#CourseName").change(function () {

            var courseID = $(this).val();
            $.ajax({
                type: 'POST',
                url: '@Url.Action("FillCourseInfo","Student")', // we are calling json method
                dataType: 'json',
                data: { StudentID: @ViewBag.studentID, CourseID, courseID  },


                success: function (ret) {
            $('#Dates').val(ret.courseDates); 
                    $('#Project').val(ret.projectName);
                    $('#Graduated').val(ret.graduated);

                },
                error: function (ex) {
                    //alert('Failed to retrieve states.' + ex);
                }
            });

            return false;
        });

Change your controller function with below function

public JsonResult FillCourseInfo(int StudentID, int CourseID)
{
     var ret = (from e in db.Enrollments 
               join c in db.Courses on e.CourseID equals c.CourseID
               where e.StudentID == StudentID && e.CourseID == CourseID
               select new StudentCourseDetails
               {
                   courseDates = c.CourseStartDate.ToString() + " " + c.CourseEndDate.ToString(),
                   projectName = e.Project.ProjectTitle,
                   graduated = e.Graduated

               });
    return Json(ret);
}