L2S Repository

l2s_repository.cs

public abstract class LinqToSqlRepository : IDisposable
{
    private readonly DataContext _dc;

    protected LinqToSqlRepository()
    {
        _dc = DataContext;
    }

    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;
    }

    protected abstract DataContext DataContext { get; }
}