L2S Repository

l2s_repository.cs

    public class LinqToSqlRepository<TContext> 
                 : IDisposable where TContext : DataContext, new()
    {
        private readonly DataContext _dc;

        public LinqToSqlRepository()
        {
            _dc = new TContext();
        }

        public T Load<T>(object id) where T : class
        {
            return _dc.GetTable<T>().SingleOrDefault(BuildWhereClause<T>(id));
        }

        public void Update<T>(T entity) where T : class
        {
            _dc.SubmitChanges();
        }

        public void Insert<T>(T entity) where T : class
        {
            _dc.GetTable<T>().InsertOnSubmit(entity);
            _dc.SubmitChanges();
        }

        public void Insert<T>(IEnumerable<T> entities) where T : class
        {
            _dc.GetTable<T>().InsertAllOnSubmit(entities);
            _dc.SubmitChanges();
        }

        public IQueryable<T> Query<T>() where T : class
        {
            return _dc.GetTable<T>();
        }

        public void Delete<T>(T entity) where T : class
        {
            _dc.GetTable<T>().DeleteOnSubmit(entity);
            _dc.SubmitChanges();
        }

        public void DeleteAll<T>(IEnumerable<T> entities) where T : class
        {
            _dc.GetTable<T>().DeleteAllOnSubmit(entities);
            _dc.SubmitChanges();
        }

        public void Dispose()
        {
            _dc.Dispose();
        }

        private Expression<Func<T, bool>> BuildWhereClause<T>(object id) where T : class
        {
            var parameter = Expression.Parameter(typeof(T));
            var whereExpression = Expression.Lambda<Func<T, bool>>
            (
            Expression.Equal(Expression
                               .Property(parameter
                                   , GetPrimaryKeyName<T>())
                                   , Expression.Constant(id))
                                   , new[] { parameter }
                             );
            return whereExpression;
        }

        private string GetPrimaryKeyName<T>()
        {
            var primaryKey = _dc.Mapping
                                .GetMetaType(typeof(T))
                                .DataMembers
                                .SingleOrDefault(m => m.IsPrimaryKey);

            if (primaryKey == null)
                throw new MissingPrimaryKeyException();

            return primaryKey.Name;
        }
    }