From SQL database to model using linq - c#

For my homework I need to get the data with a c# application using Entity Framework out of a SQL database.
The problem is that I have no idea what I am doing wrong.
My class:
public class Organisation
{
public int Id { get; set; }
public string Name { get; set; }
public Organisation(int Id, string Name)
{
this.Id = Id;
this.Name = Name;
}
public class OrganisationContext : DbContext
{
public DbSet<Organisation> Organisations { get; set; }
}
public static Organisation Find(int id) {
using (var context = new OrganisationContext())
{
// Query for all blogs with names starting with B
var organisation = from b in context.Organisations
where b.Id = id
select b;
return organisation;
}
}
}
My user class. I use Identity.
public class ApplicationUser : IdentityUser
{
public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
{
// Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
// Add custom user claims here
return userIdentity;
}
public string Firstname { get; set; }
public string Interjunction { get; set; }
public string Lastname { get; set; }
public int OrganisationId { get; set; }
public virtual Organisation Organisation
{
get
{
return Organisation.Find(OrganisationId);
}
}
public int Role { get; set; }
public string DisplayName
{
get
{
string dspFirstname = string.IsNullOrWhiteSpace(this.Firstname) ? "" : this.Firstname;
string dspInterjunction = string.IsNullOrWhiteSpace(this.Interjunction) ? "" : this.Interjunction + " ";
string dspLastname = string.IsNullOrWhiteSpace(this.Lastname) ? "" : this.Lastname;
return string.Format("{0} {1}{2}", dspFirstname, dspInterjunction, dspLastname);
}
}
}
public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
public ApplicationDbContext()
: base("DefaultConnection", throwIfV1Schema: false)
{
}
public static ApplicationDbContext Create()
{
return new ApplicationDbContext();
}
}
I am searching and trying to understand it for a while but how do I convert a var to an organisation model? Or am I missing an important peace of code?


Ok. In your method you want to return single Organization object:
public static Organisation Find(int id)
But your LINQ query actually returns a collection of objects:
using (var context = new OrganisationContext())
{
// Query for all blogs with names starting with B
var organisation = from b in context.Organisations
where b.Id = id
select b;
return organisation;
}
In this case you are filtering organization by primary key and there is no situation when this query returns more then 1 row. Then you can just call SingleOrDefault():
var organisation = (from b in context.Organisations
where b.Id = id
select b).SingleOrDefault();
return organisation;
Also, you can use Find method from DbSet class:
using (var context = new OrganisationContext())
{
// Query for all blogs with names starting with B
var organisation = context.Organisations.Find(id)
return organisation;
}
One of the common requirements for entities in EF is parameterless constructor. So, you need to remove existed constroctor for Organization class or add another one:
public Organization() { }

Related

adding new property to asp.net identity role [duplicate]

I'm trying to use the new ASP.NET Identity in my MVC5 application, specifically I'm trying to integrate ASP.NET Identity into an existing database. I've already read the questions/answers on SO pertaining to DB First and ASP.NET Identity, and having followed all the recommendations I still can't add roles to my database, although I have no problems adding users. Here's my code:
var context = new PayrollDBEntities();
var roleManager = new RoleManager<AspNetRole>(new RoleStore<AspNetRole>(context));
bool roleExists = roleManager.RoleExists(roleDto.Name);
if (roleExists){
return false;
}
var role = new AspNetRole(roleDto.Name){
Name = roleDto.Name,
};
IdentityResult result = roleManager.Create(role);//Getting exception here
At the last line of code I get an exception of type 'System.InvalidOperationException': The entity type IdentityRole is not part of the model for the current context.
Here is my context:
public partial class PayrollDBEntities : IdentityDbContext
{
public PayrollDBEntities()
: base("name=PayrollDBEntities")
{
}
public virtual DbSet<AspNetRole> AspNetRoles { get; set; }
public virtual DbSet<AspNetUserClaim> AspNetUserClaims { get; set; }
public virtual DbSet<AspNetUserLogin> AspNetUserLogins { get; set; }
public virtual DbSet<AspNetUser> AspNetUsers { get; set; }
......
}
My AspNetUser and AspNetRole classes derive from IdentityUser and IdentityRole respectively, but I'm still getting that exception. Here is my database diagram:
Any help would be greatly appreciated.

You have to specify during the creation of User Store that AspNetRole is used instead of IdentityRole. You can achieve this by using the UserStore class with 6 type parameters:
new UserStore<AspNetUser, AspNetRole, string, IdentityUserLogin, IdentityUserRole, IdentityUserClaim>(new PayrollDBEntities());
This indicates changes at User Manager creation as well. Here is a simplified example about the creation of needed instances:
public class AspNetUser : IdentityUser { /*customization*/ }
public class AspNetRole : IdentityRole { /*customization*/ }
public class PayrollDBEntities : IdentityDbContext //or : IdentityDbContext <AspNetUser, AspNetRole, string, IdentityUserLogin, IdentityUserRole, IdentityUserClaim>
{
}
public class Factory
{
public IdentityDbContext DbContext
{
get
{
return new PayrollDBEntities();
}
}
public UserStore<AspNetUser, AspNetRole, string, IdentityUserLogin, IdentityUserRole, IdentityUserClaim> UserStore
{
get
{
return new UserStore<AspNetUser, AspNetRole, string, IdentityUserLogin, IdentityUserRole, IdentityUserClaim>(DbContext);
}
}
public UserManager<AspNetUser, string> UserManager
{
get
{
return new UserManager<AspNetUser, string>(UserStore);
}
}
public RoleStore<AspNetRole> RoleStore
{
get
{
return new RoleStore<AspNetRole>(DbContext);
}
}
public RoleManager<AspNetRole> RoleManager
{
get
{
return new RoleManager<AspNetRole>(RoleStore);
}
}
}

After a few days of trying to get this to work in a clean manner, I've come to the conclusion that if you're using Database first and want to integrate ASP.NET Identity into your app, by far the easiest and cleanest solution is to create your own membership provider by overriding ASP.NET Identity. It's actually pretty easy, so far I've implemented UserStore and RoleStore to my liking. I've added columns/relations specific to my domain in my database, and whenever I create a user or a role, I take care of my database commits by adding the required relations. My UserStore implementation is quite similar to this. My RoleStore implementation is something like this:
public class ApplicationRoleStore : IRoleStore<ApplicationRoleDTO>
{
private PayrollDBEntities _context;
public ApplicationRoleStore() { }
public ApplicationRoleStore(PayrollDBEntities database)
{
_context = database;
}
public Task CreateAsync(ApplicationRoleDTO role)
{
if (role == null)
{
throw new ArgumentNullException("RoleIsRequired");
}
var roleEntity = ConvertApplicationRoleDTOToAspNetRole(role);
_context.AspNetRoles.Add(roleEntity);
return _context.SaveChangesAsync();
}
public Task DeleteAsync(ApplicationRoleDTO role)
{
var roleEntity = _context.AspNetRoles.FirstOrDefault(x => x.Id == role.Id);
if (roleEntity == null) throw new InvalidOperationException("No such role exists!");
_context.AspNetRoles.Remove(roleEntity);
return _context.SaveChangesAsync();
}
public Task<ApplicationRoleDTO> FindByIdAsync(string roleId)
{
var role = _context.AspNetRoles.FirstOrDefault(x => x.Id == roleId);
var result = role == null
? null
: ConvertAspNetRoleToApplicationRoleDTO(role);
return Task.FromResult(result);
}
public Task<ApplicationRoleDTO> FindByNameAsync(string roleName)
{
var role = _context.AspNetRoles.FirstOrDefault(x => x.Name == roleName);
var result = role == null
? null
: ConvertAspNetRoleToApplicationRoleDTO(role);
return Task.FromResult(result);
}
public Task UpdateAsync(ApplicationRoleDTO role)
{
return _context.SaveChangesAsync();
}
public void Dispose()
{
_context.Dispose();
}
private ApplicationRoleDTO ConvertAspNetRoleToApplicationRoleDTO(AspNetRole aspRole)
{
return new ApplicationRoleDTO{
Id = aspRole.Id,
EnterpriseId = aspRole.EnterpriseId,
Name = aspRole.Name
};
}
private AspNetRole ConvertApplicationRoleDTOToAspNetRole(ApplicationRoleDTO appRole)
{
return new AspNetRole{
Id = appRole.Id,
EnterpriseId = appRole.EnterpriseId,
Name = appRole.Name,
};
}
}
And my ApplicationRoleDTO:
public class ApplicationRoleDTO : IRole
{
public ApplicationRoleDTO()
{
Id = Guid.NewGuid().ToString();
}
public ApplicationRoleDTO(string roleName)
: this()
{
Name = roleName;
}
public string Id { get; set; }
public string Name { get; set; }
public Guid EnterpriseId { get; set; }
}
I also found these 2 articles pretty helpful:
Overview of Custom Storage Providers for ASP.NET Identity
Implementing a Custom MySQL ASP.NET Identity Storage Provider

I'll explain here with the code exampels :).
The trick is, they are already in the IdentityDbContext (AspNetRoles, AspNetUserClaims, AspNetUsers, ....)
In the IdentityModel you will see ApplicationUser is empty at the top. If you want to customize these users or roles, just add properties here and then update your database via the console
Example of my context
public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
public ApplicationDbContext()
: base("DefaultConnection")
{
}
public DbSet<Request> Requests { get; set; }
public DbSet<Reservation> Reservations { get; set; }
public DbSet<PriceType> PriceTypes { get; set; }
public DbSet<Product> Products { get; set; }
public DbSet<Price> Prices { get; set; }
public DbSet<GuestbookPost> Posts { get; set; }
public DbSet<Count> Counts { get; set; }
public DbSet<Invoice> Invoices { get; set; }
public DbSet<InvoiceLine> InvoiceLines { get; set; }
...
}
So no application user is defined here, but I did add more properties to it, example:
public class ApplicationUser : IdentityUser
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string GroupName { get; set; }
public string Email { get; set; }
[StringLength(15)]
public string Phone { get; set; }
public string Remark { get; set; }
public DateTime? BirthDate { get; set; }
public DateTime ValidFrom { get; set; }
public DateTime ValidUntil { get; set; }
public string Street { get; set; }
public string ZipCode { get; set; }
public string City { get; set; }
public virtual ICollection<Request> Requests { get; set; }
}

I know this is an old question, but just in case someone else is having a hard time adding roles/users when they modified asp identity to use numeric primary keys (int/long) instead of the default string for the Identity Roles, so if you have changed the IdentityUserRole in IdentityModels.cs to something like this:
public class Role : IdentityRole<long, UserRole>
{
public Role() { }
public Role(string name) { Name = name; }
}
You have to use the class Role instead of the default IdentityRole when constructing the RoleManager, so your code should be like this:
public static void RegisterUserRoles()
{
ApplicationDbContext context = new ApplicationDbContext();
var RoleManager = new RoleManager<Role, long>(new RoleStore(context));
if (!RoleManager.RoleExists("Administrador"))
{
var adminRole = new Role {
Name = "Administrador",
};
RoleManager.Create(adminRole);
}
}
So this should populate your database properly, I think all experienced ASP programmers already know this, but for others this could take some time to figure out.

I solved with a different way.
First I splited in two different Projects and Contexts.
My project that Handle the Identity has this context:
public class ApplicationDbContext : IdentityDbContext<ApplicationUser>, IDisposable
{
public ApplicationDbContext()
: base("DefaultConnection", throwIfV1Schema: false)
{
}
public static ApplicationDbContext Create()
{
return new ApplicationDbContext();
}
}
This is my ApplicationUser:
public class ApplicationUser : IdentityUser
{
//Put here the extra properties that Identity does not handle
[Required]
[MaxLength(150)]
public string Nome { get; set; }
public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
{
// Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
// Add custom user claims here
return userIdentity;
}
}
And my ApplicationUserManager looks like this:
public class ApplicationUserManager : UserManager<ApplicationUser>
{
public ApplicationUserManager(IUserStore<ApplicationUser> store)
: base(store)
{
//Setting validator to user name
UserValidator = new UserValidator<ApplicationUser>(this)
{
AllowOnlyAlphanumericUserNames = false,
RequireUniqueEmail = true
};
//Validation Logic and Password complexity
PasswordValidator = new PasswordValidator
{
RequiredLength = 6,
RequireNonLetterOrDigit = false,
RequireDigit = false,
RequireLowercase = false,
RequireUppercase = false,
};
//Lockout
UserLockoutEnabledByDefault = true;
DefaultAccountLockoutTimeSpan = TimeSpan.FromMinutes(5);
MaxFailedAccessAttemptsBeforeLockout = 5;
// Providers de Two Factor Autentication
RegisterTwoFactorProvider("Código via SMS", new PhoneNumberTokenProvider<ApplicationUser>
{
MessageFormat = "Seu código de segurança é: {0}"
});
RegisterTwoFactorProvider("Código via E-mail", new EmailTokenProvider<ApplicationUser>
{
Subject = "Código de Segurança",
BodyFormat = "Seu código de segurança é: {0}"
});
//Email service
EmailService = new EmailService();
// Definindo a classe de serviço de SMS
SmsService = new SmsService();
var provider = new DpapiDataProtectionProvider("Braian");
var dataProtector = provider.Create("ASP.NET Identity");
UserTokenProvider = new DataProtectorTokenProvider<ApplicationUser>(dataProtector);
}
}
I hope that this helps someone.
This solution was from this article:
Eduardo Pires - But it is in Portuguese

I fixed this issue by changing the web.config DefaultConnection connectionString property so it points to the new SQLServer database

how to limit GET api call based on user properties

I have a many to many relationship between ApplicationUser and a model "Companies"
I want the signed in user to only be able to retrieve documents that are assigned to their company(s).
Using this linq statement
public IEnumerable<DocumentResult> GetDocuments()
{
var manager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(new ApplicationDbContext()));
var user = manager.FindById(User.Identity.GetUserId());
return db.Documents
.Where(j => j.Company.Name == user.Companies)
.ToResults();
}
I am getting this
Operator '==' cannot be applied to operands of type 'string' and 'ICollection'
Models
public class Company
{
public Company()
{
Users = new HashSet<ApplicationUser>();
}
public int Id { get; set; }
public string Name { get; set; }
public ICollection<ApplicationUser> Users { get; set; }
}
ApplicationUser
public class ApplicationUser : IdentityUser
{
public ApplicationUser()
{
Companies = new HashSet<Company>();
}
public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
{
// Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
// Add custom user claims here
return userIdentity;
}
public ICollection<Company> Companies { get; set; }
public string FullName { get; set; }
public string ProfilePicUrl { get; set; }
}

Consider using code like this:
db.Documents
.Where(j => user.Companies.Any(uc=>uc.Name == j.Company.Name));
.ToResults();

The error msg is clear.
user.Companies is a collection,j.Company.Name is string.
You can not use the "==" to compare string with the the different type.

How to load linked entities with IdentityUser and Entity Framework

I'm currently writing a small test application to understand how IdentityUser works.
I've created a MyUser class that inherits from IdentityUser. The only additional property on my custom user class is a collection of my Book class.
I've created methods on the controller that successfully store new users to the database and associated Books. The problem is when I try to retrieve a user, the Books collection for that user is not populated - it's always null.
When I check the database I can see that a Book is stored in the database with an associated User ID however I can't seem to retrieve this collection.
Here is what I have so far:
Book.cs:
public class Book
{
public int Id { get; set; }
public string Isbn { get; set; }
public string Title { get; set; }
public string Author { get; set; }
}
MyUser.cs:
public class MyUser : IdentityUser
{
public IList<Book> Books { get; set; }
}
MyAppContext.cs:
public class MyAppContext : IdentityDbContext<MyUser>
{
public MyAppContext() : base("MyApp")
{
}
public DbSet<Book> Books { get; set; }
}
AuthRepository:
public class AuthRepository : IDisposable
{
private MyAppContext _ctx;
private UserManager<MyUser> _userManager;
public AuthRepository()
{
_ctx = new MyAppContext();
_userManager = new UserManager<MyUser>(new UserStore<MyUser>(_ctx));
}
public async Task<IdentityResult> RegisterUser(RegistrationModel userModel)
{
MyUser user = new MyUser();
user.UserName = userModel.UserName;
var result = await _userManager.CreateAsync(user, userModel.Password);
return result;
}
public async Task<IdentityResult> UpdateUser(MyUser userModel)
{
var result = await _userManager.UpdateAsync(userModel);
return result;
}
public async Task<MyUser> FindUser(string userName, string password)
{
var user = await _userManager.FindAsync(userName, password);
return user;
}
public async Task<MyUser> GetUser(string userName)
{
var user = await _userManager.FindByNameAsync(userName);
return user;
}
public void Dispose()
{
_ctx.Dispose();
_userManager.Dispose();
}
}
I figured maybe within the GetUser() method I could manually retrieve all books from the Book table with _ctx.Books.Where(b => b.MyUser_id == user.Id) however intellisense isn't even giving me the MyUser_Id property on the Books table.
I'm not really sure how to go about this. All I want to do is load all the associated books for a user automatically but I'm not sure how to do this. Any ideas?
Thanks

Your class for Book doesn't include user information for the foreign key reference. Try adding
[ForeignKey("UserId")]
public MyUser User { get; set; }
to the Book class definition.
When you get the users with the query
_ctx.Users.Include(u=> u.Books)
The books for each user should be included.

EF4.1 : How to deal with items being added to an Object's collection

I'm using EF4.1 for the first time (so be patient with me) but I just cant get to grips with how I can add new items to a sub collection of an object and then save the object.
For example, with the classes below, I can initially save the TravelTicket (containing multiple People) into my database, but as soon as I add a new person and then try to save the TravelTicket again I get:
An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.
Can anyone help?
public class TravelTicket
{
public int Id { get; set; }
public string Destination { get; set; }
public virtual List<Person> Members { get; set; }
}
public class Person
{
public int Id { get; set; }
public string Name{ get; set; }
}
EDITED: All relevant code added as requested:
Domain Models:
public class TravelTicket
{
public int Id { get; set; }
public string Destination { get; set; }
public virtual ICollection<Person> Members { get; set; }
}
public class Person
{
public int Id { get; set; }
public string Name { get; set; }
}
The DB Context:
public class TicketContext : DbContext
{
public TicketContext()
: base("TicketStore")
{ }
public DbSet<TravelTicket> TravelTickets { get; set; }
public DbSet<Person> People { get; set; }
}
The Repository (relevant methods only):
public class TicketRepository : ITicketRepository
{
TicketContext context = new TicketContext();
public void InsertOrUpdate(TravelTicket quoteContainer)
{
if (quoteContainer.Id == default(int))
{
// New entity
context.TravelTickets.Add(quoteContainer);
}
else
{
// Existing entity
context.Entry(quoteContainer).State = EntityState.Modified;
}
}
public void Save()
{
try
{
context.SaveChanges();
}
catch (DbEntityValidationException dbEx)
{
foreach (var validationErrors in dbEx.EntityValidationErrors)
{
foreach (var validationError in validationErrors.ValidationErrors)
{
Trace.TraceInformation("Property: {0} Error: {1}", validationError.PropertyName, validationError.ErrorMessage);
}
}
}
}
}
public interface ITicketRepository
{
void InsertOrUpdate(TravelTicket travelTicket);
void Save();
}
The consuming (example) MVC Controller code:
public class TicketSaleController : Controller
{
private readonly ITicketRepository ticketRepository;
public TicketSaleController()
: this(new TicketRepository())
{
}
public TicketSaleController(ITicketRepository ticketRepository)
{
this.ticketRepository = ticketRepository;
}
public ActionResult Index()
{
TravelTicket ticket = new TravelTicket();
ticket.Destination = "USA";
List<Person> travellers = new List<Person>();
travellers.Add(new Person { Name = "Tom" });
travellers.Add(new Person { Name = "Dick" });
travellers.Add(new Person { Name = "Harry" });
ticket.Members = travellers;
ticketRepository.InsertOrUpdate(ticket);
ticketRepository.Save();
Session["Ticket"] = ticket;
return RedirectToAction("Next");
}
public ActionResult Next()
{
TravelTicket ticket = (TravelTicket)Session["Ticket"];
ticket.Members.Add(new Person { Name = "Peter" });
ticket.Members.Add(new Person { Name = "Paul" });
ticketRepository.InsertOrUpdate(ticket);
ticketRepository.Save();
return View();
}
}
The call "ticketRepository.InsertOrUpdate(ticket);" on the "Next" method causes the exception:
An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.
FURTHER EDIT: If I pull the object back from the database after its been saved instead of pulling the object from the session, adding the 2 new persons works OK:
Works:
TravelTicket ticket = ticketRepository.Find(ticketId);
ticket.Members.Add(new Person { Name = "Peter" });
ticket.Members.Add(new Person { Name = "Paul" });
ticketRepository.InsertOrUpdate(ticket);
ticketRepository.Save();
Doesn't Work:
TravelTicket ticket = (TravelTicket)Session["Ticket"];
ticket.Members.Add(new Person { Name = "Peter" });
ticket.Members.Add(new Person { Name = "Paul" });
ticketRepository.InsertOrUpdate(ticket);
ticketRepository.Save();

I'd need to see the code you are using to add items and then persist them. Until that a few generic advice.
It seems like you're using a long-living context to do your stuff. It's a good practice to use short living context, like this:
Instance context
Do a single operation
Dispose the context
Rinse and repeat for every operation you have to do. While following this good practice, you could be indirectly solving your problem.
Again, for more specific help, please post the code you're using ;)

In your mapping class for person, you may need do something like this
Property(p => p.Id)
.StoreGeneratedPattern = StoreGeneratedPattern.Identity;

How to test if my linq query went through

This is my code from my controller:
MGEntities db = new MGEntities();
[HttpPost]
public ActionResult Register(RegisterModel model)
{
if (ModelState.IsValid)
{
// Attempt to register the user
MembershipCreateStatus createStatus = MembershipService.CreateUser(model.UserName, model.Password, model.Email);
if (createStatus == MembershipCreateStatus.Success)
{
FormsService.SignIn(model.UserName, false /* createPersistentCookie */);
MembershipUser myObject = Membership.GetUser();
Guid UserID = (Guid)myObject.ProviderUserKey;
MyProfile profile = new MyProfile();
profile.Address = model.Address;
profile.City = model.City;
profile.Zip = model.Zip;
profile.State = model.State;
profile.UserId = UserID;
Debug.Write(profile.State);
db.aspnet_Profiles.Add(profile);
return RedirectToAction("Index", "Home");
}
else
{
ModelState.AddModelError("", AccountValidation.ErrorCodeToString(createStatus));
}
}
This is my MyProfile Class:
namespace MatchGaming.Models
{
[Bind(Exclude = "ProfileId")]
public class MyProfile
{
[Key]
[ScaffoldColumn(false)]
public int ProfileId { get; set; }
public Guid UserId { get; set; }
[DisplayName("Address")]
public string Address { get; set; }
[DisplayName("City")]
public string City { get; set; }
[DisplayName("Zip")]
public string Zip { get; set; }
[DisplayName("State")]
public string State { get; set; }
}
}
After the linq query is executed, i check my database and nothing is added. I am using POCO for my entities. Here is my class:
namespace MatchGaming.Models
{
public class MGEntities : DbContext
{
public DbSet<MyProfile> aspnet_Profiles { get; set; }
}
}
I basically just dont understand why its not adding to the database, if theres a way I can check if the query went through correctly or not or if anyone can see the problem. Thank you!

Try
db.aspnet_Profiles.Add(profile);
db.SaveChanges();

You're misusing EF.
EF contexts are not thread safe and cannot be reused across requests.
You need to create a separate context (MGEntities) for each request, by creating it in the controller in a using statement.
You also need to call SaveChanges().

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