對于大量數(shù)據(jù)的查詢和展示使用分頁是一種不錯的選擇，這篇文章簡要介紹下自己實(shí)現(xiàn)分頁查詢的思路。
分頁需要三個變量：數(shù)據(jù)總量、每頁顯示的數(shù)據(jù)條數(shù)、當(dāng)前頁碼。
//數(shù)據(jù)總量
int dataCount;
//每頁顯示的數(shù)據(jù)條數(shù)
int pageDataCount;
int pageNumber;
根據(jù)數(shù)據(jù)總量和每頁顯示的數(shù)據(jù)條數(shù)計算出總頁數(shù)，根據(jù)當(dāng)前頁碼和每頁顯示的數(shù)據(jù)條數(shù)計算出從數(shù)據(jù)庫中讀取數(shù)據(jù)的起始行號和結(jié)束行號。
//總頁數(shù)
int pageCount = (int)Math.Ceiling(dataCount/ (pageDataCount* 1.0));
int startLine = (pageNumber - 1) * PageDataCount + 1;
int endLine=startLine + PageDataCount - 1;
對于數(shù)據(jù)庫的查詢操作使用輕量級ORM框架Dapper來實(shí)現(xiàn)，具體代碼如下：
protected IDbConnection CreateConnection()
{
IDbConnection dbConnection = new SqlConnection(ConnectionString);
dbConnection.Open();
return dbConnection;
}
//獲取數(shù)據(jù)庫中數(shù)據(jù)的總條數(shù)
public virtual int QueryDataCount(string tableName)
{
using (IDbConnection dbConnection = CreateConnection())
{
var queryResult = dbConnection.Query<int>("select count(Id) from " + tableName);
if (queryResult == null || !queryResult.Any())
{
return 0;
}
return queryResult.First();
}
}
public virtual IEnumerable<T> RangeQuery<T>(string tableName, int startline, int endline)
{
if (string.IsNullOrEmpty(tableName))
{
throw new ArgumentNullException("表名不得為空或null");
}
if (startline <= 0)
{
throw new ArgumentOutOfRangeException("起始行號必須大于0");
}
if (endline - startline < 0)
{
throw new ArgumentOutOfRangeException("結(jié)束行號不得小于起始行號");
}
using (IDbConnection dbConnection = CreateConnection())
{
var queryResult = dbConnection.Query<T>("select top " + (endline - startline + 1) + " * from " + tableName + " where Id not in (select top " + (startline - 1) + " Id from " + tableName + " order by Id desc) order by Id desc");
if (queryResult != null && queryResult.Any())
{
return queryResult;
}
}
return null;
}
繪制分頁按鈕
在App_Code文件夾中添加PageHelper.cshtml文件封裝繪制按鈕的代碼，這里需要注意一點(diǎn)，使用VS發(fā)布站點(diǎn)時App_Code文件夾中的文件不會被打包，需要手動拷貝App_Code文件夾中的文件到站點(diǎn)中。
@*
amount：數(shù)據(jù)總數(shù)，count：每頁顯示的數(shù)據(jù)條數(shù)，redierctUrl點(diǎn)擊按鈕時的跳轉(zhuǎn)鏈接
頁面上需引用：bootstrap.min.css
*@
@helper CreatePaginateButton(int amount, int count, string redirectUrl)
{
<div id="pagenumber" style="position:fixed;bottom:-15px;text-align:center;width:84%">
<nav style="text-align:center">
<ul class="pagination">
<li><a href="@redirectUrl/1">首頁</a></li>
@{
int pageNumber = (int)Math.Ceiling(amount / (count * 1.0));
pageNumber = pageNumber < 1 ? 1 : pageNumber;
//頁面上顯示的按鈕數(shù)目（不計首頁、末頁、上一頁、下一頁等按鈕），若頁面總數(shù)超過該值則繪制按鈕分隔符
const int BUTTON_COUNT = 7;
// 按鈕分隔符
const string BUTTON_SEPARATOR = "......";
//按鈕分隔符左側(cè)按鈕數(shù)目（不計首頁、末頁、上一頁、下一頁等按鈕）
const int LEFT_BUTTON_COUNT = 4;
//按鈕分隔符右側(cè)按鈕數(shù)目（不計首頁、末頁、上一頁、下一頁等按鈕）
const int RIGHT_BUTTON_COUNT = 2;
string[] urlSegments = Request.Url.Segments;
int selectedIndex = 0;
int.TryParse(urlSegments[urlSegments.Length - 1], out selectedIndex);
int previous = (selectedIndex - 1) <= 0 ? 1 : selectedIndex - 1;
int next = (selectedIndex + 1 > pageNumber) ? pageNumber : selectedIndex + 1;
var r=Request.Cookies[""];
if (pageNumber > BUTTON_COUNT)
{
<li><a id="next" href="@redirectUrl/@previous">上一頁</a></li>
for (int i = 1; i <= BUTTON_COUNT; i++)
{
if ( selectedIndex >= LEFT_BUTTON_COUNT && selectedIndex%LEFT_BUTTON_COUNT==0 && i <= LEFT_BUTTON_COUNT)
{
<li><a name="pageButton" id="@selectedIndex" href="@redirectUrl/@selectedIndex">@selectedIndex</a></li>
int step = selectedIndex;
int tag = 0;
for (i = 1; i <= LEFT_BUTTON_COUNT; i++)
{
tag = i + step;
if (tag > pageNumber - RIGHT_BUTTON_COUNT)
{
if (i <= LEFT_BUTTON_COUNT)
{
i = LEFT_BUTTON_COUNT + 1;
}
break;
}
<li><a name="pageButton" id="@tag" href="@redirectUrl/@tag">@tag</a></li>
}
}
else if (i <= LEFT_BUTTON_COUNT && selectedIndex<LEFT_BUTTON_COUNT)
{
<li><a name="pageButton" id="@i" href="@redirectUrl/@i">@i</a></li>
}
else if (i < LEFT_BUTTON_COUNT && selectedIndex>LEFT_BUTTON_COUNT)
{
int step = selectedIndex / LEFT_BUTTON_COUNT;
int tag = 0;
<li><a name="pageButton" id="@(step*LEFT_BUTTON_COUNT)" href="@redirectUrl/@(step*LEFT_BUTTON_COUNT)">@(step*LEFT_BUTTON_COUNT)</a></li>
for (i = 1; i <= LEFT_BUTTON_COUNT; i++)
{
tag = i + step * LEFT_BUTTON_COUNT;
if (tag > pageNumber - RIGHT_BUTTON_COUNT)
{
if (i <= LEFT_BUTTON_COUNT)
{
i = LEFT_BUTTON_COUNT + 1;
}
break;
}
<li><a name="pageButton" id="@tag" href="@redirectUrl/@tag">@tag</a></li>
}
}
//繪制按鈕分隔符右側(cè)按鈕
if (i==BUTTON_COUNT-1)
{
<li><a name="pageButton" id="@(pageNumber-1)" href="@redirectUrl/@(pageNumber-1)">@(pageNumber-1)</a></li>
}
else if(i==BUTTON_COUNT)
{
<li><a name="pageButton" id="@pageNumber" href="@redirectUrl/@pageNumber">@pageNumber</a></li>
}
//繪制按鈕分隔符
else if (i >= BUTTON_COUNT -RIGHT_BUTTON_COUNT)
{
<li><span name="pageButton">@BUTTON_SEPARATOR</span></li>
}
}
<li><a id="next" href="@redirectUrl/@next">下一頁</a></li>
}
else
{
for (int i = 1; i <= pageNumber; i++)
{
<li><a name="pageButton" id="@i" href="@redirectUrl/@i">@i</a></li>
}
}
}
<li><a href="@redirectUrl/@pageNumber">末頁</a></li>
</ul>
</nav>
</div>
<script>
$(function () {
//設(shè)置被選中按鈕的背景色
var selected = $('#@selectedIndex');
if (selected != undefined) {
selected.css('background-color', '#E1E1E1');
}
</script>
}
在前臺頁面中調(diào)用即可繪制分頁按鈕
@PageHelper.CreatePaginateButton(246, 10, "/usermanager/attentionlist/")
下面是幾張分頁按鈕效果圖：
分頁按鈕效果圖
對應(yīng)的HTML代碼：
分頁按鈕HTML代碼
以上是自己對于實(shí)現(xiàn)分頁的思路，繪制分頁按鈕的方法過長，不是一個好的方案，若各位讀者有更好的解決方案還望告知。文章最后推薦一個簡單易用的分頁組件X.PagedList。
