ASP.Net 一步一步学习分页，适合初学者

1. 方式一,原始分页:

适应性比较好,但代码结构凌乱,分页链接的生成参见 GetPageLinks()函数

SQLHelper db = new SQLHelper(g_ConnStr);

db.Open();

DataSet dt = db.ExecuteDataSet("SELECT * FROM [DCMS_Article] where channel_);

if (dt.Tables[0].Rows.Count != 0)

{

int nPageSize = 10;

int nShowNum = 5;

int nRecord = dt.Tables[0].Rows.Count;

int CurPage = Utils.ToInt(Request.QueryString["page"]);

PagedDataSource fenye = new PagedDataSource();

fenye.AllowPaging = true;

fenye.DataSource = dt.Tables[0].DefaultView;

fenye.PageSize = nPageSize;

int PageCount = fenye.PageCount;

CurPage = CurPage == 0 ? 1 : CurPage;

CurPage = CurPage > PageCount ? PageCount : CurPage;

fenye.CurrentPageIndex = CurPage - 1;

rpt_list_news.DataSource = fenye;

lblPageLinks.Text = PageCount > 0 ? Utils.GetPageLinks(nRecord, nPageSize, nShowNum) : "";

}

else

{

rpt_list_news.DataSource = dt;

}

rpt_list_news.DataBind();

db.Close();

2.方式二,换个方式简化调用:

稍微简化了调用方式,但使用有一定局限性

private void Bind()

{

SQLHelper db = new SQLHelper(g_ConnStr);

db.Open();

string strsql="SELECT * FROM [DCMS_Article] where channel_ ;

int nPageSize = 2;

int nShowNum = 5;

int nRecord =0;

int CurPage = Utils.ToInt(Utils.Get( "page"));

DataSet dt = db.GetPagedDataSet(strsql, CurPage, nPageSize, out nRecord);

rpt_list_news.DataSource = dt.Tables[0];

lblPageLinks.Text = Utils.GetPageLinks(nRecord, nPageSize, nShowNum);

rpt_list_news.DataBind();

db.Close();

}

用到的GetPagedDataSet函数如下

public DataSet GetPagedDataSet(string SQLString, int CurPage, int PageSize, out int RecordCount)

{

DataSet ds = new DataSet();

using (SqlDataAdapter da = new SqlDataAdapter(SQLString, conn))

{

SQLString = System.Text.RegularExpressions.Regex.Replace(SQLString, "order by.*" , "");

RecordCount = (int)ExecuteScalar(string.Format("select count(*) from ({0}) as temp", SQLString));

//内部校正一下当前页的页码

PageSize = PageSize > 0 ? PageSize : 1;

int nPageCount = RecordCount % PageSize == 0 ? RecordCount / PageSize : (RecordCount / PageSize) + 1;

CurPage = CurPage > nPageCount ? nPageCount : CurPage;

CurPage = CurPage > 0 ? CurPage : 1;

int startRow = (CurPage - 1) * PageSize;

da.Fill(ds,startRow, PageSize, "table");

}

return ds;

}

3.初次封装简化参数:

尝试再次改进,方法二中代码看起来已经不那么乱了,但是需要提前设定多个分页参数,调用多了修改起来就比较麻烦,而且很明显的缺点适用性不好,如果我们将分页的具体操作封装就会简化许多,看封装后的调用

private void Bind()

{

SQLHelper db = new SQLHelper(g_ConnStr);

db.Open();

PageHelper pager = new PageHelper();

pager.CurrPage = Utils.ToInt(Utils .Get("page"));

int nRecord= 0;

string strsql = "SELECT * FROM [DCMS_Article] where channel_ ;

DataSet dt = db.GetPagedDataSet(strsql, pager.CurrPage, pager.PageSize, out nRecord);

rpt_list_news.DataSource = dt.Tables[0];

rpt_list_news.DataBind();

pager.RecordCount = nRecord;

lblPageLinks.Text = pager.GetPageLinks();

db.Close();

}

清晰了不少,PageHelper类提供了分页的必须参数,参数设定了默认值,另外将 Utils.GetPageLinks() 函数封装在里面内部调用默认参数,也避免参数手动输入,PageHelper 每个人都有不同的实现,大抵都类似

4.

PageHelper返回

这个PageHelper根据查询结果重新分页,跟第一次的分页方式相同,PageHelper增加了GetPagedDataSource函数

private void Bind()

{

SQLHelper db = new SQLHelper(g_ConnStr);

db.Open();

string strsql = "SELECT * FROM [DCMS_Article] where channel_ ;

DataSet dt = db.ExecuteDataSet(strsql);

PageHelper pager = new PageHelper();

pager.CurrPage = Utils.ToInt(Utils.Get("page"));

rpt_list_news.DataSource = pager.GetPagedDataSource(dt);

rpt_list_news.DataBind();

lblPageLinks.Text = pager.GetPageLinks();

db.Close();

}

public object GetPagedDataSource(DataSet dsSrc)

{

object retDataSource = new object();

if (dsSrc.Tables[0].Rows.Count != 0)

{

System.Web.UI.WebControls.PagedDataSource fenye = new System.Web.UI.WebControls.PagedDataSource();

fenye.AllowPaging = true;

fenye.DataSource = dsSrc.Tables[0].DefaultView;

fenye.PageSize = this.PageSize;

this._RecordCount = dsSrc.Tables[0].Rows.Count;

this._PageCount = fenye.PageCount;

_CurrPage = _CurrPage == 0 ? 1 : _CurrPage;

_CurrPage = _CurrPage > _PageCount ? _PageCount : _CurrPage;

fenye.CurrentPageIndex = _CurrPage - 1;

retDataSource = fenye;

}

return retDataSource;

}

这次倒是感觉跟平常的调用没啥区别了,就是多次查询让人很不爽,其次数据多了也增加开销,这里暂时先不尝试存储过程分页,再试试看能改进到什么程度

5.综合一下

数据源的获取放在PageHelper类中不是很好还是放在DBHeler中,其实我还是比较喜欢 SqlDataAdapter 来分页, PagedDataSource 分页则必须先查询一次再分页,奈何无论采取哪种方式获取记录总数总是个问题

private void Bind()

{

SQLHelper db = new SQLHelper(g_ConnStr);

db.Open();

string strsql = "SELECT * FROM [DCMS_Article] where channel_ ;

PageHelper pager = new PageHelper();

pager.CurrPage = Utils.ToInt(Utils.Get("page"));

rpt_list_news.DataSource = db.GetPagedDataSource(strsql, ref pager);

rpt_list_news.DataBind();

lblPageLinks.Text = pager.GetPageLinks();

db.Close();

}

调用算是比较简单了,要是能解决查询记录总数的问题,那就好多了,下面是DBHelper中的函数实现

public object GetPagedDataSource(string strsql, int CurrPage, int PageSize, out int RecordCount)

{

object retDataSource = new object();

DataSet dsSrc = ExecuteDataSet(strsql);

RecordCount = 0;

int PageCount = 0;

if (dsSrc.Tables[0].Rows.Count != 0)

{

System.Web.UI.WebControls. PagedDataSource fenye = new System.Web.UI.WebControls.PagedDataSource ();

fenye.AllowPaging = true;

fenye.DataSource = dsSrc.Tables[0].DefaultView;

fenye.PageSize = PageSize;

RecordCount = dsSrc.Tables[0].Rows.Count;

PageCount = fenye.PageCount;

CurrPage = CurrPage == 0 ? 1 : CurrPage;

CurrPage = CurrPage > PageCount ? CurrPage : CurrPage;

fenye.CurrentPageIndex = CurrPage - 1;

retDataSource = fenye;

}

return retDataSource;

}

//这个简化了参数调用

public object GetPagedDataSource(string strsql, ref PageHelper pager )

{

int nRecord = 0;

object retobj= GetPagedDataSource(strsql, pager.CurrPage, pager.PageSize, out nRecord);

pager.RecordCount= nRecord;

return retobj;

}