FindBy method Entity framework - asp.net-mvc-3

Question

I have this account Model:
public class Account :IAggregateRoot
{
public Account()
{
}
public Account(Guid accountId)
{
Id = accountId;
}
public Guid Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Email { get; set; }
}
}
and this repository class :
public class Repository<T> : IRepository<T> where T : class, IAggregateRoot
{
private readonly DbSet<T> _entitySet;
public T FindBy(T entity)
{
return _entitySet.Find(entity);
}
}
and now when I want to get an entity by Id , for example :
public AccountViewModel GetAccountBy(Guid accountId)
{
var account = new Account(accountId);
_unitOfWork.AccountRepository.FindBy(account);
var accountView = account.ConvertToAccountView();
return accountView;
}
I got this Error :
The specified parameter type is not valid. Only scalar types, such as System.Int32, System.Decimal, System.DateTime, and System.Guid, are supported.
my action to call GetAccountBy is like this:
public ActionResult Edit(Guid accountId)
{
var account = _accountService.GetAccountBy(accountId);
return View(account);
}
what is problem with this ? Any help is much appreciated.

Answer 1

You're not calling the DBSet.Find() method correctly.
As the documentation states you need to pass
The values of the primary key for the entity to be found
you don't pass in an instance of the entity, you pass in the key values that identify an entity. From your example you don't need to create a new instance of account:
var account = new Account(accountId);
_unitOfWork.AccountRepository.FindBy(account);
you just need to pass the accountId to FindBy()
_unitOfWork.AccountRepository.FindBy(accountId);
Here's your code amended:
public class Repository<T> : IRepository<T> where T : class, IAggregateRoot
{
private readonly DbSet<T> _entitySet;
public T FindBy(params Object[] keyValues)
{
return _entitySet.Find(keyValues)
}
}
public AccountViewModel GetAccountBy(Guid accountId)
{
_unitOfWork.AccountRepository.FindBy(accountId);
var accountView = account.ConvertToAccountView();
return accountView;
}

Answer 2

You can call the DbSet.Find(params object[] keyValues) Method only with System.Int32 and System.Guid as the error message indicates. (well and System.Decimal, System.DateTime probably for composite keys)
The method will not look for a Id or PK in your Model and use it automatically (when you pass Account, the method will not use Account.Id) - as its using "the primary key value" http://msdn.microsoft.com/en-us/library/gg696418(v=vs.103).aspx
Consider passing a predicate as suggested in FindBy Id method in EntityFramework
If you Models always have an Id of Type Guid, then maybe you can pass the Id directly:
public T FindBy(T entity)
{
return _entitySet.Find(entity.Id);
}
Hope this helps.