So I have this demo project almost completely working. public class Project { public

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Asked: May 24, 20262026-05-24T02:54:17+00:00 2026-05-24T02:54:17+00:00

So I have this demo project almost completely working. public class Project { public

0

So I have this demo project almost completely working.

public class Project
    {
        public int ID { get; set; }
        [Required]
        public string Name { get; set; }
        public virtual ICollection<Task> Tasks { get; set; }

    }

    public class Task
    {
        public int ID { get; set; }
        [Required]
        public string Name { get; set; }
        public int ProjectID { get; set; }

        public virtual Project Project { get; set; }

    }

Controller

public ActionResult Edit(int id)
        {           
            var project = db.Projects.Where(p=>p.ID==id).Single();
            return View(project);
        }

        [HttpPost]
        public ActionResult Edit(Project project)
        {
            if (ModelState.IsValid)
            {
                var dbProject = db.Projects.Where(p => p.ID == project.ID).Single();

                UpdateModel(dbProject);
                db.SaveChanges();                
                TempData["Success"] = "Modelo Valido";
            }
            return RedirectToAction("Index");
        }

View//strongly typed for project

@using (Html.BeginForm())
{
    @Html.ValidationSummary(true)
    <fieldset>
        <legend>Project</legend>
        @Html.HiddenFor(model => model.ID)
        <div class="editor-label">
            @Html.LabelFor(model => model.Name)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Name)
            @Html.ValidationMessageFor(model => model.Name)
        </div>
        <h1>Tasks</h1>
        @Html.EditorFor(m => m.Tasks)
        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
}

EditorTemplate

@model MvcApplication2.Models.Task
<span>Task</span>
<br />
    @Html.LabelFor(m => m.Name)
    @Html.EditorFor(m => m.Name)
    @Html.HiddenFor(m => m.ID)
    @Html.HiddenFor(m => m.ProjectID)
    @Html.ValidationMessageFor(m => m.Name)

The view displays this

enter image description here

The problem is that when I submit the form the Tasks are populated with everything except the virtual Project property… so the error i get it is

The operation failed: The relationship could not be changed because
one or more of the foreign-key properties is non-nullable. When a
change is made to a relationship, the related foreign-key property is
set to a null value. If the foreign-key does not support null values,
a new relationship must be defined, the foreign-key property must be
assigned another non-null value, or the unrelated object must be
deleted.

Here is a pic of my debugging breakpoint result

enter image description here

Please Help.

UPDATE:

I have changed my controller action to this

[HttpPost]
        public ActionResult Edit(Project project)
        {
            if (ModelState.IsValid)
            {
                db.Entry(project).State = EntityState.Modified;
                db.SaveChanges();                
                TempData["Success"] = "Modelo Valido";
                return RedirectToAction("Index");
            }
            return View(project);
        }

it is still not working correctly.
Now changes made to the Name of the project are updated correctly in the database. but changes made to any Task Name are ignored completely.