// open your connection / datareader etc.

List<Customer> customers = new List<Customer>();

while(dataReader.Read())
{
 Customer c = new Customer();
 c.Id = dataReader.GetInt32(0);
 c.Name = dataReader.GetString(1);
 // etc (you might want to use string indexers instead of ints for the get methods)

 customers.Add(c);
}

// close and dispose your datareader / connection etc as usual

return View("List", customers);

private DataTable GetData()
{
    DataTable dt = new DataTable();

    using (SqlConnection connection
             = new SqlConnection("ConnectionString"))
    using (SqlCommand command = new SqlCommand())
    {
        command.Connection = connection;
        command.CommandText = "SELECT * FROM Customers";

        connection.Open();
        using (SqlDataReader reader =
            command.ExecuteReader
                (CommandBehavior.CloseConnection))
        {
            dt.Load(reader);
        }
    }

    return dt;
}