namespace DAL
{
 public   class xueshengbiaos
    {


   

     public  xueshengbiaos xs(string username)
     {






         string sql = "select *  from xueshengbiaos where usernames=@username";
         List<SqlParameter> pra = new List<SqlParameter>();
         pra.Add(new SqlParameter("@usernames", username));
        DataTable dt= SqlHelper.ExecuteDataTable(sql, pra);




        
     
     }
     


    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;

namespace DAL
{
    public class SqlHelper
    {
        private static readonly string connString = ConfigurationManager.ConnectionStrings["name"].ConnectionString;
        public static int ExecuteNonQuery(string sql,params SqlParameter[] parameters )
        {
            using (SqlConnection conn = new SqlConnection(connString))
            {
                conn.Open();
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                   cmd.Parameters.AddRange(parameters);
                   return cmd.ExecuteNonQuery();
                }
            }
        }
        public static object ExecuteScalar(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connString))
            {
                conn.Open();
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteScalar();
                }
            }
        }
        public static DataTable ExecuteDataTable(string sql, params SqlParameter[] parameters)
        {
            DataSet set = new DataSet();
            using (SqlConnection conn = new SqlConnection(connString))
            {
                conn.Open();
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    if (parameters!=null)
                    {
                        cmd.Parameters.AddRange(parameters); 
                    }
                    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                    adapter.Fill(set);
                    return set.Tables[0];
                }
            }
        }

        internal static void ExecuteDataTable(string sql, List<SqlParameter> pra)
        {
            throw new NotImplementedException();
        }
    }
}