User-164452226 posted
Good day Tech Gurus,
l want to use drop down list to select fields from two tables and save the data to another table. Here is what l have.
1) From the Course Entity select CourseCode
public class Course
{
[Key]
public int CourseID { get; set; }
public string CourseCode { get; set; }
public string CourseName { get; set; }
}
2) From the IntakeDetail Entity select IntakeID
public class IntakeDetail
{
public int Id { get; set; }
[Key]
public string IntakeID { get; set; }
public string IntakeName { get; set; }
public string CollegeID { get; set; }
}
3) The Entity to be populated
public class StudentCourse
{
[Key]
public int EnrollmentID { get; set; }
public string StudentID { get; set; }
public string CourseCode { get; set; }
public string IntakeID { get; set; }
[NotMapped]
public List<Course> CourseList { get; set; }
[NotMapped]
public List<IntakeDetail> IntakeList { get; set; }
}
4) My EFStudentCourseRepository
public class EFStudentCourseRepository : IStudentCourseRepository
{
private EFDbContext context = new EFDbContext();
public IEnumerable<StudentCourse> StudentCourses
{
get { return context.StudentCourses; }
}
public void SaveStudentCourse(StudentCourse studentCourse)
{
if (studentCourse.EnrollmentID == 0)
{
context.StudentCourses.Add(studentCourse);
}
context.SaveChanges();
}
}
5) My StudentCourseController
[HttpPost]
EFStudentCourseRepository repository = new EFStudentCourseRepository();
public ActionResult Save(StudentCourse studentCourse)
{
EFCourseRepository courseRepository = new EFCourseRepository();
studentCourse.CourseList = courseRepository.Courses.ToList<Course>();
EFIntakeRepository intakeRepository = new EFIntakeRepository();
studentCourse.IntakeList = intakeRepository.IntakeDetails.ToList<IntakeDetail>();
if (ModelState.IsValid)
{
repository.SaveStudentCourse(studentCourse);
TempData["message"] = string.Format("Student successfully enorolled for {0} Course", studentCourse.CourseCode);
return RedirectToAction("StudentSubjectList");
}
else
{ // there is something wrong with the data values
return View("studentCourse");
}
}
6) My Save View (In this view l was trying to use Drop down list to fetch the CourseCode by l need to do the same for IntakeID)
@using (Html.BeginForm("Save", "StudentCourse", FormMethod.Post))
{
@Html.AntiForgeryToken()
<div class="form-horizontal">
<h4>UserLogin</h4>
<hr />
@Html.ValidationSummary(true, "", new { @class = "text-danger" })
<div class="form-group">
@Html.LabelFor(model => model.StudentID, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.EditorFor(model => model.StudentID, new { htmlAttributes = new { @class = "form-control" } })
@Html.ValidationMessageFor(model => model.StudentID, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
@*@foreach (var c in Model.CourseCode)
{
@Html.Partial("CourseList", c)
}*@
@Html.LabelFor(x => Model.CourseCode, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.DropDownListFor(Model => Model.CourseCode, new SelectList(Model.CourseList, "CourseCode", "CourseName"), "Select")
@Html.ValidationMessageFor(model => model.CourseCode, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
@Html.LabelFor(model => model.IntakeID, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.EditorFor(model => model.IntakeID, new { htmlAttributes = new { @class = "form-control" } })
@Html.ValidationMessageFor(model => model.IntakeID, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
<div class="col-md-offset-2 col-md-10">
<input type="submit" value="Create" class="btn btn-default" />
</div>
</div>
</div>
}
7) Error Message l am getting
Server Error in '/' Application.
Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.
Source Error:
Line 34:
Line 35: <div class="col-md-10">
Line 36: @Html.DropDownListFor(Model => Model.CourseCode, new SelectList(Model.CourseList, "CourseCode", "CourseName"), "Select")
Line 37:
Line 38: @Html.ValidationMessageFor(model => model.CourseCode, "", new { @class = "text-danger" })
Source File: C:\Users\TMATIWURE\source\repos\CollegeSys\CollegeSys.WebUI\Views\StudentCourse\Save.cshtml Line: 36
Please Help, and it looks like l will need to use these drop down list to select from tables and save to another table in many parts of my project so l am stuck.
