Updating column in ASP.NET mvc 5 creates new row - asp.net

Question

I'm following this tutorial to create a modified version of a blog. In this case, the "posts" are the same things as "projects," the "tags" are called "technologies," and the comments are all the same. In this case, the create new post/project function also should be able to update existing posts/projects. When I click submit, however, editing an old post, it simply creates a new one.
Here is my controller:
[Authorize]
[HttpPost]
[ValidateAntiForgeryToken]
[ValidateInput(false)]
public ActionResult Update(int? p, string title, string shortDescription, string longDescription, DateTime dateTime, string technologies)
{
Project project = GetProject(p);
if (!User.IsInRole("ChapterAdvisor") || !(User.Identity.GetFirstName() + " " + User.Identity.GetLastName()).Equals(project.ProjectLeader))
{
RedirectToAction("Index");
}
project.Title = title;
project.ShortDescription = shortDescription;
project.LongDescription = longDescription;
project.TimeCreated = dateTime;
project.ProjectLeader = User.Identity.GetFirstName() + " " + User.Identity.GetLastName();
project.Technologies.Clear();
technologies = technologies ?? string.Empty;
string[] technologyNames = technologies.Split(new char[] {' '}, StringSplitOptions.RemoveEmptyEntries);
foreach (string technologyName in technologyNames)
{
project.Technologies.Add(GetTechnology(technologyName));
}
if (!p.HasValue)
{
model.Projects.Add(project);
}
try
{
model.SaveChanges();
}
catch (System.Data.Entity.Validation.DbEntityValidationException dbEx)
{
Exception raise = dbEx;
foreach (var validationErrors in dbEx.EntityValidationErrors)
{
foreach (var validationError in validationErrors.ValidationErrors)
{
string message = string.Format("{0}:{1}",
validationErrors.Entry.Entity.ToString(),
validationError.ErrorMessage);
// raise a new exception nesting
// the current instance as InnerException
raise = new InvalidOperationException(message, raise);
}
}
throw raise;
}
return RedirectToAction("Details", new { p = project.Id });
}
public ActionResult Edit(int? p)
{
Project project = GetProject(p);
StringBuilder technologyList = new StringBuilder();
foreach (Technology technology in project.Technologies)
{
technologyList.AppendFormat("{0} ", technology.Name);
}
ViewBag.Technologies = technologyList.ToString();
return View(project);
}
private Technology GetTechnology(string technologyName)
{
return model.Technologies.Where(x => x.Name == technologyName).FirstOrDefault() ?? new Technology() { Name = technologyName };
}
private Project GetProject(int? id) => id.HasValue ? model.Projects.Where(x => x.Id == id).First() : new Project() { Id = -1 };
And this is my view:
<form action="#Href("~/Projects/Update")" method="post" id="postForm">
#Html.AntiForgeryToken()
#if (Model.Id != -1)
{
<input type="hidden" value="#Model.Id" />
}
#{ DateTime dateTime = Model.TimeCreated.Year > 2000 ? Model.TimeCreated : DateTime.Now; }
<input type="text" name="dateTime" value="#dateTime" /> Date<br />
<input type="text" name="title" value="#Model.Title" /> Project Name<br />
#Html.DropDownListFor(m => m.Technologies, new SelectList(new List<Object> { new { value = "Animation", text = "Animation" }, new { value = "Robotics", text = "Robotics" }, new { value = "Architecture", text = "Architecture" }, new { value = "CAD", text = "CAD" }, new { value = "Websites", text = "Websites" }, new { value = "Games", text = "Games" }, new { value = "Biotechnology", text = "Biotechnology" }, new { value = "Club", text = "Club" }, new { value = "Other", text = "Other" } }, "value", "text"), new { #style = "border: 1px solid #e8e8e8;padding: 0.5em 1.07em 0.5em;background: #f5f5f5;font-size: 0.875rem;border-radius: 5px;width: 100%;line-height: 1.43;min-height: 3.5em;" })
<textarea name="shortDescription" rows="5" cols="80">#Model.ShortDescription</textarea><br />
<textarea name="longDescription" rows="10" cols="80">#Model.LongDescription</textarea><br />
<input type="submit" name="submit" value="Save Changes" />
</form>
Any ideas why it is creating a new "project" instead of updating the one defined by the variable passed in the url?

Answer 1

Every post from that form is being treated as a "new" record because it doesn't contain the ID from an existing record. So the logic always assumes it's new.
This is because the hidden input isn't included in the POST data because it has no name:
<input type="hidden" value="#Model.Id" />
It looks like your action expects the ID value to be called "p":
<input type="hidden" name="p" value="#Model.Id" />