asp.net访问数据库的方式

using System;
using System.Data;
using System.Data.SqlClient;

public class DatabaseHelper
{
    private string connectionString = "your_connection_string";

    public DataTable ExecuteQuery(string sql)
    {
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();
            SqlCommand command = new SqlCommand(sql, connection);
            SqlDataAdapter adapter = new SqlDataAdapter(command);
            DataTable result = new DataTable();
            adapter.Fill(result);
            return result;
        }
    }
}

using System;
using System.Data.Entity;

public class ApplicationDbContext : DbContext
{
    public DbSet<User> Users { get; set; }

    public ApplicationDbContext() : base("your_connection_string")
    {
    }
}

public class User
{
    public int Id { get; set; }
    public string Name { get; set