linq to sql 学习（6）linq的分页实例

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前面我们学习完了LINQ to SQL 的增删改查，对LINQ应该有比较熟悉的了解，这节我们接之前的 linq to sql 学习（4）增删改查实例来继续学习关于LINQ的分页。

①，我们首先来改造下List.aspx页面的代码：（主要是增加了分页的几个按钮）

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="List.aspx.cs" Inherits="LinqDemo.List" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

</head>

<body>

<div>

<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="true">

</asp:ScriptManager>

<tr>

<td>

id:<asp:TextBox ID="txt_id" runat="server"></asp:TextBox>

</td>

<td>

名称<asp:TextBox ID="txt_proname" runat="server"></asp:TextBox>

</td>

<td>

数量:<asp:TextBox ID="txt_insertcount" runat="server"></asp:TextBox>

</td>

<td>

<asp:Button ID="btnQuery" runat="server" OnClick="btnQuery_Click" Text="查询" />

<asp:Button ID="btndelete" runat="server" Text="删除" OnClick="btndelete_Click" />

<asp:Button ID="btnAdd" runat="server" Text="添加" OnClick="btnAdd_Click" />

<asp:Button ID="btnUpdate" runat="server" Text="修改" OnClick="btnUpdate_Click" />

</td>

</tr>

<tr>

<asp:UpdatePanel runat="server" ID="up">

<asp:GridView ID="GridView1" runat="server" Width="100%" AutoGenerateColumns="False">

<asp:TemplateField>

<asp:CheckBox runat="server" ID="chkall" AutoPostBack="true" OnCheckedChanged="chkall_CheckedChanged" />

</HeaderTemplate>

</ItemTemplate>

</asp:TemplateField>

<asp:BoundField DataField="id" HeaderText="id" />

<asp:BoundField DataField="proname" HeaderText="名称" />

<asp:BoundField DataField="insertday" HeaderText="入货时间" />

<asp:BoundField DataField="insertcount" HeaderText="入货数量" />

</Columns>

</asp:GridView>

<asp:LinkButton runat="server" ID="lbFirstPage" OnClick="lbFirstPage_Click">第一页</asp:LinkButton>

<asp:LinkButton runat="server" ID="lbFrontPage" OnClick="lbFrontPage_Click">上一页</asp:LinkButton>

<asp:LinkButton runat="server" ID="lbNextPage" OnClick="lbNextPage_Click">下一页</asp:LinkButton>

<asp:LinkButton runat="server" ID="lbEndPage" OnClick="lbEndPage_Click">最后一页</asp:LinkButton>

总条数：<asp:Label ID="lblAllCount" runat="server" Text=""></asp:Label>

当前页：<asp:Label ID="lblCurrentPage" runat="server" Text=""></asp:Label>

总页数：<asp:Label ID="lblEndPage" runat="server" Text=""></asp:Label>

</ContentTemplate>

<asp:AsyncPostBackTrigger ControlID="btnQuery" EventName="Click" />

<asp:AsyncPostBackTrigger ControlID="btndelete" EventName="Click" />

<asp:AsyncPostBackTrigger ControlID="btnAdd" EventName="Click" />

</Triggers>

</asp:UpdatePanel>

</td>

</tr>

</table>

</div>

</form>

</body>

</html>

②，改造下List.aspx.cs 代码:

using System;

using System.Collections;

using System.Configuration;

using System.Data;

using System.Linq;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Xml.Linq;

namespace LinqDemo

{

public partial class List : System.Web.UI.Page

{

//页数

public int pagesize = 5;

//当前页

public int pageindex = 0;

protected void Page_Load(object sender, EventArgs e)

{

btndelete.Attributes.Add("onclick", "javascript:return window.confirm('确定删除吗？')");

btnAdd.Attributes.Add("onclick", "javascript:return window.confirm('确定添加吗？')");

if (!IsPostBack)

{

Bind();

}

protected void btnQuery_Click(object sender, EventArgs e)

{

ViewState["pageindex"] = 0;

Bind();

}

public IQueryable<InStore> I_store

{

get

{

var predicate = PredicateBuilder.True<InStore>();

if (!string.IsNullOrEmpty(txt_proname.Text))

{

predicate = predicate.And(p => p.ProName.Contains(txt_proname.Text));

}

if (!string.IsNullOrEmpty(txt_insertcount.Text))

{

predicate = predicate.And(p => p.InsertCount.Equals(txt_insertcount.Text));

}

InStoreDataContext db = new InStoreDataContext();

if (ViewState["pageindex"] != null)

{

pageindex = Convert.ToInt32(ViewState["pageindex"]);

}

//总条数

lblAllCount.Text = db.InStore.Where(predicate).Count().ToString();

//当前页

lblCurrentPage.Text = (pageindex+1).ToString();

//总页数

lblEndPage.Text = (GetEndPage+1).ToString();

return db.InStore.Where(predicate).Skip(pageindex * pagesize).Take(pagesize);

}

/// <summary>

/// 最后一页

/// </summary>

public int GetEndPage

{

get

{

if (Convert.ToInt32(lblAllCount.Text) % pagesize == 0)

{

return Convert.ToInt32(lblAllCount.Text) / pagesize-1;

}

else

{

return Convert.ToInt32(lblAllCount.Text) / pagesize ;

}

/// <summary>

/// 判断按钮页的显示和隐藏

/// </summary>

public void SetLbEnable()

{

if (lblCurrentPage.Text == "1")

{

lbFirstPage.Enabled = false;

lbFrontPage.Enabled = false;

}

else

{

lbFirstPage.Enabled = true;

lbFrontPage.Enabled = true;

}

if (lblCurrentPage.Text == lblEndPage.Text)

{

lbEndPage.Enabled = false;

lbNextPage.Enabled = false;

}

else

{

lbEndPage.Enabled = true;

lbNextPage.Enabled = true;

}

/// <summary>

/// 查询函数

/// </summary>

private void Bind()

{

GridView1.DataSource = I_store;

GridView1.DataBind();

SetLbEnable();

}

/// <summary>

/// 添加函数

/// </summary>

/// <param name="sender"></param>

/// <param name="e"></param>

protected void btnAdd_Click(object sender, EventArgs e)

{

InStoreDataContext db = new InStoreDataContext();

InStore store = new InStore();

store.Id = int.Parse(txt_id.Text);

store.InsertCount = int.Parse(txt_insertcount.Text);

store.InsertDay = DateTime.Now;

store.ProName = txt_proname.Text;

db.InStore.InsertOnSubmit(store);

db.SubmitChanges();

txt_insertcount.Text = "";

txt_proname.Text = "";

txt_id.Text = "";

Bind();

}

/// <summary>

/// 删除函数

/// </summary>

/// <param name="sender"></param>

/// <param name="e"></param>

protected void btndelete_Click(object sender, EventArgs e)

{

InStoreDataContext db = new InStoreDataContext();

for (int i = 0; i < GridView1.Rows.Count; i++)

{

HtmlInputCheckBox chk = (HtmlInputCheckBox)GridView1.Rows[i].FindControl("chk");

if (chk.Checked)

{

InStore store = db.InStore.First(p => p.Id.Equals(int.Parse(chk.Value)));

db.InStore.DeleteOnSubmit(store);

db.SubmitChanges();

}

Bind();

}

/// <summary>

/// 修改函数

/// </summary>

/// <param name="sender"></param>

/// <param name="e"></param>

protected void btnUpdate_Click(object sender, EventArgs e)

{

InStoreDataContext db = new InStoreDataContext();

for (int i = 0; i < GridView1.Rows.Count; i++)

{

HtmlInputCheckBox chk = (HtmlInputCheckBox)GridView1.Rows[i].FindControl("chk");

if (chk.Checked)

{

InStore store = db.InStore.First(p => p.Id.Equals(int.Parse(chk.Value)));

Response.Redirect("edit.aspx?id=" + chk.Value + "");

}

/// <summary>

/// 首页

/// </summary>

/// <param name="sender"></param>

/// <param name="e"></param>

protected void lbFirstPage_Click(object sender, EventArgs e)

{

ViewState["pageindex"] = 0;

Bind();

}

/// <summary>

/// 下一页

/// </summary>

/// <param name="sender"></param>

/// <param name="e"></param>

protected void lbNextPage_Click(object sender, EventArgs e)

{

ViewState["pageindex"] = Convert.ToInt32(ViewState["pageindex"]) + 1;

Bind();

}

/// <summary>

/// 上一页

/// </summary>

/// <param name="sender"></param>

/// <param name="e"></param>

protected void lbFrontPage_Click(object sender, EventArgs e)

{

ViewState["pageindex"] = Convert.ToInt32(ViewState["pageindex"]) - 1;

Bind();

}

/// <summary>

/// 最后一页

/// </summary>

/// <param name="sender"></param>

/// <param name="e"></param>

protected void lbEndPage_Click(object sender, EventArgs e)

{

ViewState["pageindex"] = GetEndPage;

Bind();

}

//全选

protected void chkall_CheckedChanged(object sender, EventArgs e)

{

for (int i = 0; i < GridView1.Rows.Count; i++)

{

CheckBox chkall = (CheckBox)GridView1.HeaderRow.FindControl("chkall");

HtmlInputCheckBox chk = (HtmlInputCheckBox)GridView1.Rows[i].FindControl("chk");

if (chkall.Checked == true)

{

chk.Checked = true;

}

else

{

chk.Checked = false;

}

运行后效果图如下：

备注：LINQ的分页功能，主要是两个属性，Skip,代表的是从第几条数据开始算起，Take代表的是每页的产生的条数。

例如：

db.InStore.Where(predicate).Skip(0).Take(5); 代表的是从第1条数据开始，产生5条数据，

db.InStore.Where(predicate).Skip(5).Take(5); 代表的是从第6条数据开始，产生5条数据。