"Object reference not set to an instance of an object" when trying to use if statement in a foreach loop

Question

I have a table which shows every enrollment a student has to a course. I have a foreach loop looping through all the enrollments for the student

@foreach (var item in Model.Enrollments)
{
    <tr>
        <td> @Html.DisplayFor(modelItem => item.Course.CourseID) </td>
        <td> @Html.DisplayFor(modelItem => item.Course.Title) </td>
        <td> @Html.DisplayFor(modelItem => item.Course.Type) </td>
        <td> @Html.DisplayFor(modelItem => item.Status) </td>
    </tr>     
}

Now this works all fine as expected, but when I try to show only courses that have a certain type using an if statement

@foreach (var item in Model.Enrollments)
{
if (item.Course.Type == "Basic Core") 
   {
    <tr>
        <td> @Html.DisplayFor(modelItem => item.Course.CourseID) </td>
        <td> @Html.DisplayFor(modelItem => item.Course.Title) </td>
        <td> @Html.DisplayFor(modelItem => item.Course.Type) </td>
        <td> @Html.DisplayFor(modelItem => item.Status) </td>
    </tr>
   }                              
}

I get

"Object reference not set to an instance of an object." error on line 115

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 113:{
Line 114:
Line 115:    if (item.Course.Type == "Basic Core") {
Line 116:        <tr>
Line 117:            <td> @Html.DisplayFor(modelItem => item.Course.CourseID) </td>

In my understanding a foreach loop would skip any null objects if there are any. Any help would be greatly appreciated.

Here is my controller

public ActionResult Details(int? StudentID)
{
    if (StudentID == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
    Student student = db.Students.Find(StudentID);
    if (student == null)
    {
        return HttpNotFound();
    }
    return View(student);
}

Your inner `Course` object is null that's why the error. Check for null before if condition — Mahesh, Feb 09 '15 at 07:43

score 0 · Accepted Answer · answered Feb 09 '15 at 07:49

As Coder of Code pointed, you have got an item object that contains a Course object set to null.

Since the item object is not null it's picked up from enumeration. Then while checking the inner Course object it is throwing the exception as it is null. To avoid just check for null before evaluating the object like so:

@foreach (var item in Model.Enrollments)
{
if (item.Course != null && item.Course.Type == "Basic Core") 
   {
    <tr>
        <td> @Html.DisplayFor(modelItem => item.Course.CourseID) </td>
        <td> @Html.DisplayFor(modelItem => item.Course.Title) </td>
        <td> @Html.DisplayFor(modelItem => item.Course.Type) </td>
        <td> @Html.DisplayFor(modelItem => item.Status) </td>
    </tr>
   }                              
}

You could also debug the razor code to see what's happening if required.

Thank you, your comment solved the problem and illustrated the solution perfectly. — Niko Kallio, Feb 10 '15 at 08:14

"Object reference not set to an instance of an object" when trying to use if statement in a foreach loop

1 Answers1