Double Edit ActionResult with [AllowAnonymous] and [Authorize] - asp.net-mvc

Question

I have this problem: I can not create a double "Edit" ActionResult into a controller where my goal is to allow an anonymous user to change a number of fields through a filter that returns only one record in the output .... The system returns this error, and I knew, somehow, that the problem is related to the primary key.
CONTROLLER
// GET:
[Authorize]
public async Task<ActionResult> Edit(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
MyTable mytable = await db.MyTable.FindAsync(id);
if (mytable == null)
{
return HttpNotFound();
}
return View(mytable);
}
[AllowAnonymous]
[HttpGet]
public async Task<ActionResult> EditAnonymus(int? fk_field1, string guid)
{
if (fk_field1 == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
var query = (from i in db.MyTable
where i.Guid == guid && i.Fk_Field1==fk_Field1
select new { i.Id }).SingleOrDefault();
MyTable mytable = await db.MyTable.FindAsync(query.Id);
if (mytable == null)
{
return HttpNotFound();
}
return View(mytable);
}
// POST:
// To protect from overposting attacks, please enable the specific properties you want to bind to, for
// more details see http://go.microsoft.com/fwlink/?LinkId=317598.
[HttpPost]
[Authorize]
[ValidateAntiForgeryToken]
public async Task<ActionResult> Edit([Bind(Include = "Id,Fk_table1,......")] MyTable mytable)
{
if (ModelState.IsValid)
{
try
{
db.Entry(mytable).State = EntityState.Modified;
await db.SaveChangesAsync();
return RedirectToAction("Index");
}
catch (DbUpdateConcurrencyException ex)
{
Trace.Write(ex.Message);
}
}
return View(mytable);
}
[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public async Task<ActionResult> EditAnonymus([Bind(Include = "Id,........")] MyTable mytable)
{
if (ModelState.IsValid)
{
try
{
db.Entry(mytable).State = EntityState.Modified;
await db.SaveChangesAsync();
return RedirectToAction("Index");
}
catch (DbUpdateConcurrencyException ex)
{
Trace.Write(ex.Message);
}
}
return View(mytable);
}
VIEW (command for entry from another View)
#Html.ActionLink("Modify Anonymus",
"EditAnonumus", controllerName: "NameController",
routeValues: new
{ fk_table1 = Model.Id, guid = Request.QueryString["guid"] },
htmlAttributes: null)
VIEW (Edit)
#model ManagingEvent.Models.MyTable
#using (Html.BeginForm())
{
#Html.AntiForgeryToken()
<div class="form-horizontal">
<h4>Anonymus Edit</h4>
<hr />
#Html.ValidationSummary(true, "", new { #class = "text-danger" })
#Html.HiddenFor(model => model.Id)
//omiss
<div class="form-group">
#Html.LabelFor(model => model.Cognome, htmlAttributes: new { #class = "control-label col-md-2" })
<div class="col-md-10">
#Html.EditorFor(model => model.Field, new { htmlAttributes = new { #class = "form-control" } })
#Html.ValidationMessageFor(model => model.Field, "", new { #class = "text-danger" })
</div>
</div>
<div class="form-group">
<div class="col-md-offset-2 col-md-10">
<input type="submit" value="Save" class="btn btn-default" />
</div>
</div>
</div>
}
ERROR OUTPUT (after save)
Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since
entities were loaded. See
http://go.microsoft.com/fwlink/?LinkId=472540 for information on
understanding and handling optimistic concurrency exceptions.The
thread 0x518 has exited with code 0 (0x0).

Answer 1

I think your problem is not related to the primary key but can be this line of code in the EditAnonymus method:
db.Entry(mytable).State = EntityState.Modified;
What you are doing is mark explicitly the entity as modified, EF will try to update it when you call SaveChangesAsync() and will expect to get the count of the rows updated (1), but if no properties have changed it will get 0 (no rows have been updated), therefore it will throw the exception.
I would comment that row and try to do a simple fetch-edit-save and see what happens.

Answer 2

Thanks to the user449689 guidance, I searched in internet and I have found this method works:
[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public async Task<ActionResult> EditAnonymus (int? Id)
{
if (Id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
var TableToUpdate = await db.myTable.FindAsync(Id);
if (TryUpdateModel(TableToUpdate, "",
new string[] { "Field1","Field2","....","....","Field x" }))
{
try
{
db.SaveChanges();
return RedirectToAction("Index");
}
catch (DataException /* dex */)
{
//Log the error (uncomment dex variable name and add a line here to write a log.
ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists, see your system administrator.");
}
}