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The Object Context instance has been disposed and can no longer be used for operations that require a connection

Kindly tell me where I am doing a mistake I have seen StackOverflow same mistake but I am not finding my error after searchIng a lot.
This line Creates Error After Debugging
#Model.Product.category.Name
This is my front end
<div class="product-categories">
<span>Categories: </span>#Model.Product.category.Name
</div>
my View model looks like
public class ProductViewModel
{
public Product Product { get; set; }
}
This is my Entities
public class Product:BaseEntity
{
public decimal price { get; set; }
//public int CategoryID { get; set; }
public string ImageURL { get; set; }
public virtual Category category { get; set; }
}
```[Ent][3]
[Front End where an error has been raised][1]
[My Entities image for your better understanding][2]
[1]: https://i.stack.imgur.com/sHRtx.png
[2]: https://i.stack.imgur.com/CVsQQ.png
[3]: https://i.stack.imgur.com/WXOa0.png

This is my Product Service where I get Products and these lines of code are showing an error
Before Code
public Product GetProduct(int ID)
{
using (var context = new TablesContext())
{
return context.Products.Find(ID);
}
}
After Same code updated
public Product GetProduct(int ID)
{
using (var context = new TablesContext())
{
return context.Products.Where(x => x.id == ID).Include(x => x.category).FirstOrDefault();
}
}
this line of code updated from this return context.Products.Find(ID);
to this
return context.Products.Where(x => x.id == ID).Include(x => x.category).FirstOrDefault();

DateTime in the transfer parameter of the edit method in the controller is always 01.01.0001 00:00:00 asp.net mvc5

I a problem in the transfer parameter in the Edit Method "issue".
In Issue the CreatedDate and UpdatedDate is always {01.01.0001 00:00:00}.
The parameter Id, Title and Description is always correct.
My Controller:
public ActionResult Edit([Bind(Include = "Id,Title,Description")] Issue issue)
{
if (ModelState.IsValid)
{
db.Entry(issue).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
return View(issue);
}
My Model:
public class Issue : BaseEntity
{
public int Id { get; set; }
[Required(ErrorMessage = "Required")]
public string Title { get; set; }
[AllowHtml]
[Required(ErrorMessage = "Required")]
[DataType(DataType.MultilineText)]
public string Description { get; set; }
}
public class BaseEntity
{
public DateTime CreatedDate { get; set; }
public DateTime UpdatedDate { get; set; }
}
I can unfortunately can not debug from where the "issue" parameter comes from.
From where the transfer parameter "Issue issue" in the Edit method comes from and why are all DateTimes always {01.01.0001 00:00:00}?
When I create the first time a issue entity I add the DateTimme in the SaveChanges() Method with the following modification in my DBContext:
public override int SaveChanges()
{
var entries = ChangeTracker
.Entries()
.Where(e => e.Entity is BaseEntity && (
e.State == EntityState.Added
|| e.State == EntityState.Modified));
foreach (var entityEntry in entries)
{
((BaseEntity)entityEntry.Entity).UpdatedDate = DateTime.UtcNow;
if (entityEntry.State == EntityState.Added)
{
((BaseEntity)entityEntry.Entity).CreatedDate = DateTime.UtcNow;
}
}
return base.SaveChanges();
}
And the SaveChanges() works without problem. When I create the issue entity the first time the DateTime has the correct value and I can also see it in the Detail View.

Change your edit code to this
var exist = d.Set<Issue>().FindAsync(issue.Id);
if (exist == null)
{
//ErrorMessage = "Can't find item to update";
}
else{
db.Entry(exist).CurrentValues.SetValues(issue);
var result = await db.SaveChanges(); // result should be > 0
}

How to update data with child using EF Core

I have these two models:
public class Film
{
public long Id { get; set; }
[Required]
public string Title { get; set; }
[Required]
public string Director { get; set; }
public string Synopsis { get; set; }
public int? Release { get; set; }
[Required]
public Genre Genre { get; set; }
}
public class Genre
{
public long Id { get; set; }
public string Description { get; set; }
}
And I want to be able to update a Film's Genre through a PUT method. I am currently trying this, but I get the following error:
[HttpPut]
public async Task<IActionResult> UpdateFilm(Film film)
{
var existingFilm = await _context.Films
.Include(f => f.Genre)
.FirstOrDefaultAsync(f => f.Id == film.Id);
if (existingFilm == null)
{
return NotFound(new JsonResponse { Success = false, Message = "Impossible to update, film was not found", Data = null });
}
existingFilm.Title = film.Title;
existingFilm.Synopsis = film.Synopsis;
existingFilm.Release = film.Release;
existingFilm.Director = film.Director;
if (existingFilm.Genre.Id != film.Genre.Id)
{
existingFilm.Genre.Id = film.Genre.Id;
existingFilm.Genre.Description = film.Genre.Description;
//_context.Entry(existingFilm.Genre).State = EntityState.Modified;
_context.Entry(existingFilm).CurrentValues.SetValues(film);
}
_context.Films.Update(existingFilm);
try
{
await _context.SaveChangesAsync();
}
catch (Exception e)
{
return BadRequest(new JsonResponse { Success = false, Message = e.Message, Data = null });
}
return Ok(new JsonResponse { Success = true, Message = "Film updated with success", Data = film });
}
The error message is:
System.InvalidOperationException: The property 'Id' on entity type 'Genre' is part of a key and so cannot be modified or marked as modified. To change the principal of an existing entity with an identifying foreign key first delete the dependent and invoke 'SaveChanges' then associate the dependent with the new principal.
Anyone able to help? Thanks a lot.

According to the error, its existingFilm.Genre.Id that you cannot update the id, if its not equal to the id.
My suggestion would be ignore the id update, but if it is necessary:
if (existingFilm.Genre.Id != film.Genre.Id)
{
var genre = _context.Genre.FirstOrDefault(x => x.Id == film.Genre.Id);
// Update the fields needed except the id
existingFilm.Genre = genre;
}

How to Read Related Data Using LINQ/C# [one to many]

I have two related tables with one to many relationship, I m trying to get a JSON response that populates ICollection<PatPar> PatPar the controller's code below reads fine as long as I have only one related record, once I have more than one related record I get a selection exception.
These are related Models
public class PatReg
{
[NotMapped]
private Int64 _FileId;
[Key, Display(Name = "File Id"), ScaffoldColumn(false), DatabaseGenerated(DatabaseGeneratedOption.None)]
public Int64 FileId
{
get
{
return this._FileId;
}
set
{
this._FileId = value;
}
}
[Required, Display(Name = "First Name")]
public string FName { get; set; }
public ICollection<PatPar> PatPar { get; set; }
}
public class PatPar
{
[Key]
public Int64 RecId { get; set; }
[Display(Name = "Patient File Id"), Required]
public Int64 FileId { set; get; }
[Display(Name = "Partner File Id"), Required]
public Int64 ParFileId { set; get; }
[Display(Name = "Start Date"), DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true), Required]
public DateTime SDate { set; get; }
[Display(Name = "End Date"), DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
public DateTime? EDate { set; get; }
}
This is my API Controller
[HttpGet]
public IEnumerable<PatReg> GetPatReg()
{
return _context.PatReg;
}
[HttpGet("{id}")]
public async Task<IActionResult> GetPatReg([FromRoute] long id)
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
var patReg = await _context.PatReg.SingleOrDefaultAsync(m => m.FileId == id);
var parinfo = await _context.PatPar.SingleOrDefaultAsync(m => m.FileId == id); // I should select many records here
if (patReg == null)
{
return NotFound();
}
var DataRes = new {
sData = patReg
};
return Ok(DataRes);
}
I know that I should use selectMany instead of using SingleOrDefaultAsync so I tried
IEnumerable<PatPar> parinfo = await _context.PatPar.SelectMany(m => m.FileId == id);
but the compiler is giving me errors, what is the way to do it?

You should be using Where instead of SelectMany:
var result = _context.PatPar.Where(m => m.FileId == id);
SelectMany is used to retrieve a collection from each item of the iterated collection. However your condition is to check if the FileId equals some id - the resulted type is a boolean. I assume what you are trying to do is return all the times that have that FileId.
To have it with the await:
var result = await _context.PatPar.Where(m => m.FileId == id).ToListAsync();

Maybe you want actually this:
IEnumerable<PatPar> parinfo = _context.PatPar.Where(m => m.FileId == id);
SelectMany description:
Projects each element of a sequence to an IEnumerable and flattens
the resulting sequences into one sequence.
So it is needed if you want to get IEnumerable<SomeSpecificField> as the result.
However, it is applicable only if PatPar had IEnumerable<SomeType> and you want to SelectMany<PatPar, SomeType>.
In your case there can be only Select
IEnumerable<Int64> parFileIds = _context.PatPar.Select(m => m.ParFileId );

An exception of type 'System.InvalidCastException' occurred in EntityFramework.Core.dll but was not handled in user code

I am trying to get the long value associated to an ActivityLogType it is associated to either a create, edit, and delete record in the database.
It is used for an audit / activity log that is needed.
public enum ActivityLogType
{
Create = 1,
Update = 2,
Delete = 3
}
My getter method:
public ActivityType GetType(ActivityLogType type)
{
var id = (long)type;
Console.WriteLine(id); // <---- this produces a 1 in the console. So the cast works?
return _context.ActivityTypes.Where(x => x.Id == id).FirstOrDefault(); // <-- This line throws the error
}
UPDATE 1
un-lucky suggested using (long)ActivityLogType.Create to get the desired output. I tried this: (Still not working)
public ActivityType GetType(ActivityLogType type)
{
switch (type)
{
case ActivityLogType.Create:
return _context.ActivityTypes.Where(x => x.Id == (long)ActivityLogType.Create).FirstOrDefault();
case ActivityLogType.Update:
return _context.ActivityTypes.Where(x => x.Id == (long)ActivityLogType.Update).FirstOrDefault();
case ActivityLogType.Delete:
return _context.ActivityTypes.Where(x => x.Id == (long)ActivityLogType.Delete).FirstOrDefault();
default:
return null;
}
}
UPDATE 2
Here is the ActivityType entity
public class ActivityType
{
public ActivityType()
{
this.Activities = new HashSet<Activity>();
}
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public long Id { get; set; }
[Display(Name = "Label")]
public string Label { get; set; }
[Display(Name = "Display Order")]
public int Order { get; set; }
[Display(Name = "Is Active")]
public bool IsActive { get; set; }
[Display(Name = "Activities")]
public virtual ICollection<Activity> Activities { get; set; }
}

You can try this:
long id= Int64.Parse(Convert.ChangeType(type, Enum.GetUnderlyingType(type.GetType())).ToString());