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

在“引用”中需要添加System.Configuration

　　 class SqlHelper
    {
        private static string connStr = ConfigurationManager.ConnectionStrings["sqlCon"].ConnectionString;

        //使用长度可变参数来简化
        public static int ExecuteNonQuery(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = sql;
                    //foreach (SqlParameter param in parameters)
                    //{
                    //    cmd.Parameters.Add(param);
                    //}
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteNonQuery();
                }
            }
        }

        public static object ExecuteScalar(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteScalar();
                }
            }
        }

        //只用来执行查询结果比较少的sql，查询结果存入本地
        public static DataTable ExecuteDataTable(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);

                    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                    DataSet dataset = new DataSet();
                    adapter.Fill(dataset);
                    return dataset.Tables[0];
                }
            }
        }
    }