转载---ajax简单三层实现登陆

public class DAL
{
private string connstr = "Data Source=localhost;Initial Catalog=code_data;UID=sa;Password=$wuhan888;Persist Security Info=true";
public DataTable selectDB(string sql)
{
DataTable dt = new DataTable();
try
{
SqlConnection conn = new SqlConnection(connstr);
SqlDataAdapter sda = new SqlDataAdapter(sql, conn);
sda.Fill(dt);
}
catch (Exception e)
{ }
return dt;
}
}