SqlHelper

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

namespace SqlHelper
{
    class SqlHelper
    {
        //创建App.config
        //<connectionStrings>
        //    <add name="dbConnstr" connectionString="Data Source=172.0.0.0; Initial Catalog=TestDataBase;User ID=sa;Password=123456"/>
        //</connectionStrings>
        //References 引用System.Configuration
        private static string connString = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString;

        //params 长度可变参数
        //params声明的必须是最后一个参数
        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();//返回第一行第一列数据
                }
            }
        }

        public static DataSet ExecuteDataSet(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connString))
            {
                conn.Open();
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddRange(parameters);
                    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                    DataSet dataSet = new DataSet();
                    adapter.Fill(dataSet);
                    return dataSet;
                }
            }
        }

        #region 测试
        private void Main()
        {
            string sql = "select * from users where username = @UserName";
            SqlHelper.ExecuteDataSet(sql, new SqlParameter("@UserName", "Nelson"));
        }
        #endregion
    }
}

　　连接数据库最好使用  打开----操作----关闭  的方式。

　　使用 Using 不会造成资源泄露。