System.argumentnullexception: 'value cannot be null. Parameter name: entity'

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Hi Team

I am having a problem, i am saving a value column to my database table. When it reaches to the method to save that value it throws an exception as being null. How do i resolve this issue?

What I have tried:

// Model

public class eNtsaCourses
  {
      [Key]
      public Guid? Id { get; set; }
      public string Course { get; set; }
      public string Nickname { get; set; }
      public string Term { get; set; }
      public string EnrolledAs { get; set; }
      public bool Published { get; set; }
  }

//GET://Courses/Courses-All.
    [Route("Home/Courses")]
  public ActionResult Courses(RegCoursesViewModel eNtsaCourses)
    {
        if(ModelState.IsValid)
        {
            cb.eNtsaCourse.Add(eNtsaCourses.Courses);
            cb.SaveChanges(); // This gets thrown here.
        }
        return View(eNtsaCourses);
    }

[HttpPost]
      public JsonResult AddCoursesRegistration(string CourseName, string clientNo)
      {
          return Json(true, JsonRequestBehavior.AllowGet);
      }

Posted 31-Aug-20 0:01am

gcogco10

Updated 31-Aug-20 2:58am

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Comments

Richard MacCutchan 31-Aug-20 8:13am

As we have said many times, the only way to diagnose issues like this is by using the debugger to find out which item is null.

gcogco10 31-Aug-20 8:19am

@Richard the null is thrown cb.eNtsaCourse.Add(eNtsaCourses.Courses);

F-ES Sitecore 31-Aug-20 9:47am

The problem is likely to be with the view such that it isn't passing a RegCoursesViewModel.Courses object to the action.

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Sandeep Mewara · Answer 1 · 2020-08-31T02:59:00

If you say the error is at:

Quote:
cb.eNtsaCourse.Add(eNtsaCourses.Courses);

eNtsaCourses.Courses seems to be the culprit. Mostly, eNtsaCourses is null.
OR
eNtsaCourses.Courses is null.

While trying to save the value null for Courses, it throws an error. (Error at DTO/Entity level)

You need to:
1. make sure that the request holds the value if it is supposed to
2. Irrespective of request, your code should handle validations around input to avoid such errors.