Class derived from Generic Repository

问题

I have a Generic Repository class, see below, which is used to perform common Data Access functions, ie, Add, GetByID etc.

    public class GenericRepository<TEntity> : IGenericRepository<TEntity> where TEntity : class
    {
    internal GolfEntities context;
    internal DbSet<TEntity> dbSet;

    public GenericRepository(GolfEntities context)
    {
        this.context = context;
        this.dbSet = context.Set<TEntity>();
    }

    public TEntity GetByID(object id)
    {
        return dbSet.Find(id);
    }

I would like to create another Repository class that derives from this Generic Repository class so that I can carry out other functions which do not belong to the Generic Repository class, such as, get a users full name.

I have created a a class called UserRepository, see below, which derives from the Generic Repository, however, I keep getting an error when I compile:

Repository.GenericRepository< User> does not contain a constructor that takes 0 arguments

public class UserRepository : GenericRepository<User>, IUserRepository
{

    internal GolfEntities _context;

    public UserRepository() : base() { }

    public UserRepository(GolfEntities context)
    {
        _context = context;
    }

    public string FullName()
    {
        return "Full Name: Test FullName";
    }


}

Does anyone know how to fix this?

Any help would be much appreciated.

Thanks.

回答1:

You should remove the default constructor from your derived repository:

public UserRepository() : base() { }

Since your base repository class doesn't have a parameterless constructor calling base() doesn't make sense. Also you don't need to repeat the same logic in your derived constructor as in the base one. You could only invoke it:

public class UserRepository : GenericRepository<User>, IUserRepository
{
    public UserRepository(GolfEntities context): base(context)
    { 

    }

    public string FullName()
    {
        return "Full Name: Test FullName";
    }
}

回答2:

Change your UserRepository to this:

public class UserRepository : GenericRepository<User>, IUserRepository
{
    public UserRepository(GolfEntities context)
        : base (context)
    {
    }

    public string FullName()
    {
        return "Full Name: Test FullName";
    }
}

Your GenericRepository does not have a default constructor so you need to call the constructor which is expecting your GolfEntities context and pass the parameter down.

回答3:

The base (generic) repository does not have a parameterless, default constructor and so you cannot write this:

  public UserRepository() : base() { }

You need to call one of the base class constructors.

来源：https://stackoverflow.com/questions/9601057/class-derived-from-generic-repository

标签

repository

repository-pattern

derived-class