Yoann's Dev Blog

public interface IRepository<T> : IDisposable where T : class
{
    IQueryable<T> Fetch();
    IEnumerable<T> GetAll();
    IEnumerable<T> Find(Func<T, bool> predicate);
    T Single(Func<T, bool> predicate);
    T First(Func<T, bool> predicate);
    void Add(T entity);
    void Delete(T entity);
    void Attach(T entity);
    void SaveChanges();
    void SaveChanges(SaveOptions options);
}

/// <summary>
/// A generic repository for working with data in the database
/// </summary>
/// <typeparam name="T">A POCO that represents an Entity Framework entity</typeparam>
public class DataRepository<T> : IRepository<T> where T : class
{

    /// <summary>
    /// The context object for the database
    /// </summary>
    private ObjectContext _context;

    /// <summary>
    /// The IObjectSet that represents the current entity.
    /// </summary>
    private IObjectSet<T> _objectSet;

    /// <summary>
    /// Initializes a new instance of the DataRepository class
    /// </summary>
    public DataRepository()
        : this(new AdventureWorksEntities())
    {
    }

    /// <summary>
    /// Initializes a new instance of the DataRepository class
    /// </summary>
    /// <param name="context">The Entity Framework ObjectContext</param>
    public DataRepository(ObjectContext context)
    {
        _context = context;
        _objectSet = _context.CreateObjectSet<T>();
    }

    /// <summary>
    /// Gets all records as an IQueryable
    /// </summary>
    /// <returns>An IQueryable object containing the results of the query</returns>
    public IQueryable<T> Fetch()
    {
        return _objectSet;
    }

    /// <summary>
    /// Gets all records as an IEnumberable
    /// </summary>
    /// <returns>An IEnumberable object containing the results of the query</returns>
    public IEnumerable<T> GetAll()
    {
        return GetQuery().AsEnumerable();
    }

    /// <summary>
    /// Finds a record with the specified criteria
    /// </summary>
    /// <param name="predicate">Criteria to match on</param>
    /// <returns>A collection containing the results of the query</returns>
    public IEnumerable<T> Find(Func<T, bool> predicate)
    {
        return _objectSet.Where<T>(predicate);
    }

    /// <summary>
    /// Gets a single record by the specified criteria (usually the unique identifier)
    /// </summary>
    /// <param name="predicate">Criteria to match on</param>
    /// <returns>A single record that matches the specified criteria</returns>
    public T Single(Func<T, bool> predicate)
    {
        return _objectSet.Single<T>(predicate);
    }

    /// <summary>
    /// The first record matching the specified criteria
    /// </summary>
    /// <param name="predicate">Criteria to match on</param>
    /// <returns>A single record containing the first record matching the specified criteria</returns>
    public T First(Func<T, bool> predicate)
    {
        return _objectSet.First<T>(predicate);
    }

    /// <summary>
    /// Deletes the specified entitiy
    /// </summary>
    /// <param name="entity">Entity to delete</param>
    /// <exception cref="ArgumentNullException"> if <paramref name="entity"/> is null</exception>
    public void Delete(T entity)
    {
        if (entity == null)
        {
            throw new ArgumentNullException("entity");
        }

        _objectSet.DeleteObject(entity);
    }

    /// <summary>
    /// Deletes records matching the specified criteria
    /// </summary>
    /// <param name="predicate">Criteria to match on</param>
    public void Delete(Func<T, bool> predicate)
    {
        IEnumerable<T> records = from x in _objectSet.Where<T>(predicate) select x;

        foreach (T record in records)
        {
            _objectSet.DeleteObject(record);
        }
    }

    /// <summary>
    /// Adds the specified entity
    /// </summary>
    /// <param name="entity">Entity to add</param>
    /// <exception cref="ArgumentNullException"> if <paramref name="entity"/> is null</exception>
    public void Add(T entity)
    {
        if (entity == null)
        {
            throw new ArgumentNullException("entity");
        }

        _objectSet.AddObject(entity);
    }

    /// <summary>
    /// Attaches the specified entity
    /// </summary>
    /// <param name="entity">Entity to attach</param>
    public void Attach(T entity)
    {
        _objectSet.Attach(entity);
    }

    /// <summary>
    /// Saves all context changes
    /// </summary>
    public void SaveChanges()
    {
        _context.SaveChanges();
    }

    /// <summary>
    /// Saves all context changes with the specified SaveOptions
    /// </summary>
    /// <param name="options">Options for saving the context</param>
    public void SaveChanges(SaveOptions options)
    {
        _context.SaveChanges(options);
    }

    /// <summary>
    /// Releases all resources used by the WarrantManagement.DataExtract.Dal.ReportDataBase
    /// </summary>
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    /// <summary>
    /// Releases all resources used by the WarrantManagement.DataExtract.Dal.ReportDataBase
    /// </summary>
    /// <param name="disposing">A boolean value indicating whether or not to dispose managed resources</param>
    protected virtual void Dispose(bool disposing)
    {
        if (disposing)
        {
            if (_context != null)
            {
                _context.Dispose();
                _context = null;
            }
        }
    }
}

using (IRepository<Employee> repository = new DataRepository<Employee>())
{
    this.GridView1.DataSource = from x in repository.Fetch()
                                select new
                                {
                                    x.MaritalStatus,
                                    x.Contact.FirstName,
                                    x.Contact.LastName,
                                    x.BirthDate
                                };
    this.GridView1.DataBind();
}