public class SqlHelper
    {
        private readonly string _constr = ConfigurationManager.ConnectionStrings["key"].ConnectionString;

        #region 增删改通用方法
        public int ExecuteNonQuery(string sql, CommandType type, params SqlParameter[] pms)
        {
            //创建链接对象
            //创建命令对象
            //打开链接
            //执行
            using (SqlConnection con = new SqlConnection(_constr))
            {
                using (SqlCommand cmd = new SqlCommand(sql, con))
                {
                    if (pms != null)
                    {
                        cmd.Parameters.AddRange(pms);
                    }
                    cmd.CommandType = type;
                    con.Open();
                    return cmd.ExecuteNonQuery();
                }
            }
        } 
        #endregion

        #region 返回单行单列

        public object ExecuteScalar(string sql, CommandType type, params SqlParameter[] pms)
        {
            using (SqlConnection con = new SqlConnection(_constr))
            {
                using (SqlCommand cmd = new SqlCommand(sql, con))
                {
                    if (pms != null)
                    {
                        cmd.Parameters.AddRange(pms);
                    }
                    cmd.CommandType = type;
                    con.Open();
                    return cmd.ExecuteScalar();
                }
            }
        }

        #endregion

        #region datatable查询
        public DataTable ExecuteTable(string sql, CommandType type, params SqlParameter[] pms)
        {
            DataTable dt = new DataTable();
            using (SqlConnection con = new SqlConnection(_constr))
            {
                using (SqlDataAdapter cmd = new SqlDataAdapter(sql, con))
                {
                    if (pms != null)
                    {
                        cmd.SelectCommand.Parameters.AddRange(pms);
                    }
                    cmd.SelectCommand.CommandType = type;
                    con.Open();
                    cmd.Fill(dt);
                }
            }
            return dt;
        } 
        #endregion

        #region Reader查询
        public SqlDataReader ExecuteReader(string sql, CommandType type, params SqlParameter[] pms)
        {
            SqlConnection con = new SqlConnection(_constr);
            SqlCommand cmd = new SqlCommand(sql, con);
            if (pms != null)
            {
                cmd.Parameters.AddRange(pms);
            }
            cmd.CommandType = type;
            try
            {
                con.Open();
                return cmd.ExecuteReader(CommandBehavior.CloseConnection);
            }
            catch (Exception)
            {
                cmd.Dispose();
                con.Close();
                con.Dispose();
                throw;
            }
        } 
        #endregion
    }

public DataTable GetDataByPage(int start,int end)
        {
            string sql = "select * from(select *,num=ROW_NUMBER() over (order by id) from UserInfo) as t where t.num>@start and t.num<=@end";
            SqlParameter[] pms =
            {
                new SqlParameter("@start",start),
                new SqlParameter("@end",end), 
            };
            return helper.ExecuteTable(sql, CommandType.Text, pms);
        }

private void LoadData(int index)
        {
            string sql = "usp_UserInfoPage";
            SqlParameter[] pms = {
                                     new SqlParameter("@pageIndex",index),
                                     new SqlParameter("@pageSize",PageSize),
                                     new SqlParameter("@pageCount",SqlDbType.Int){Direction=ParameterDirection.Output},
                                     new SqlParameter("@totalCount",SqlDbType.Int){Direction=ParameterDirection.Output}
                                 };

            DataTable dt = db.ExecuteTable(sql, CommandType.StoredProcedure, pms);
            List<ClassInfo> list = new List<ClassInfo>();
            foreach (DataRow item in dt.Rows)
            {
                ClassInfo model = new ClassInfo();
                model.Id = Convert.ToInt32(item["Id"]);
                model.name = item["name"].ToString();
                model.pwd = item["pwd"].ToString();
                list.Add(model);
            }
            dataGridView1.DataSource = list;
            pageCount = Convert.ToInt32(pms[2].Value);
            totalCounnt = Convert.ToInt32(pms[3].Value);
            label6.Text = string.Format("{0}/{1}", index, pageCount);
        }

create database UserDB
go
use UserDB
go
create table Userinfo(
    ID int primary key identity ,
    name varchar(20) not null,
    pwd varchar(20) not null
)
insert into Userinfo values(‘sasas‘,‘1231231‘)
insert into Userinfo values(‘sasas‘,‘1231231‘)
insert into Userinfo values(‘sasas‘,‘1231231‘)
insert into Userinfo values(‘admin‘,‘123456‘)
select id,name,pwd from userinfo
go
create proc usp_UserInfoPage
@pageIndex int,
@pageSize int,
@pageCount int output,
@totalCount int output
as
begin
    --查询总条数
    select @totalCount = COUNT(*) from UserInfo
    --查询总页数
    set @pageCount = CEILING(@totalCount*1.0/@pageSize)
    --查询语句
    select * from (select *,num=ROW_NUMBER() over(order by Id) from UserInfo) as t where t.num>(@pageIndex-1)*@pageSize and t.num<=@pageIndex*@pageSize
end
select * from (select *,num=row_number() over(order by id) from userInfo) as t where t.num>0 and t.num<=4