using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            doSearch(1);
        }
    }

    private void doSearch(int page)
    {
        this.Repeater1.DataSource = null;
        this.Repeater1.DataBind();

        TestData testData=new TestData();
        List<Model> list = testData.GetData(page);

        this.Repeater1.DataSource = list;
        this.Repeater1.DataBind();
    }


    //换页,相当于你页面改变的事件.我这里没有AspNetPager1控件,我换页就直接手写数字换页
    protected void Button1_Click1(object sender, EventArgs e)
    {
        #region 这里就是把选中的checkbox中的Text保存起来，也可以是其它值，反正要能够通过这个值唯一地确定一个checkbox
        List<string> checkedModelIdList;
        var obj = Session["CheckedModelIdList"];
        if (obj == null || (obj as List<string>)==null)
            checkedModelIdList=new List<string>();
        else
        {
            checkedModelIdList = obj as List<string>;
        }

        //换页的时候先保存已选择的checkbox的ID
        foreach (RepeaterItem item in Repeater1.Items)
        {
            CheckBox chk = (CheckBox)item.FindControl("CheckBox1");
            if (chk.Checked)
            {
                if(!checkedModelIdList.Contains(chk.Text))
                {
                    checkedModelIdList.Add(chk.Text);
                }
            }
            else
            {
                if (checkedModelIdList.Contains(chk.Text))
                {
                    checkedModelIdList.Remove(chk.Text);
                }
            }
        }
        Session["CheckedModelIdList"] = checkedModelIdList;
        #endregion

        //显示新的页
        int page = 0;
        int.TryParse(TextBox1.Text.Trim(), out page);
        doSearch(page);
    }
    ///<summary>
    /// 绑定数据时做判断,再设置checkbox的选中状态
    ///</summary>
    ///<param name="sender"></param>
    ///<param name="e"></param>
    protected void Repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)
    {
        List<string> checkedModelIdList;
        var obj = Session["CheckedModelIdList"];
        if (obj == null || (obj as List<string>) == null)
            checkedModelIdList = new List<string>();
        else
        {
            checkedModelIdList = obj as List<string>;
        }
        CheckBox chk = (CheckBox)e.Item.FindControl("CheckBox1");
        chk.Checked = checkedModelIdList.Contains(chk.Text);
    }
}

///<summary>
/// 这个类是模拟数据的
///</summary>
public class TestData
{
    public List<Model> testDataList = new List<Model>();

    public TestData()
    {
        testDataList.Clear();
        testDataList.Add(new Model {ModelId = "1", ModelContent = "1axaa"});
        testDataList.Add(new Model {ModelId = "2", ModelContent = "1aavca"});
        testDataList.Add(new Model {ModelId = "3", ModelContent = "1aacxza"});
        testDataList.Add(new Model {ModelId = "4", ModelContent = "1a2aa"});
        testDataList.Add(new Model {ModelId = "5", ModelContent = "1abzxaa"});
        testDataList.Add(new Model {ModelId = "6", ModelContent = "1abaa"});
        testDataList.Add(new Model {ModelId = "7", ModelContent = "1aa  a"});
        testDataList.Add(new Model {ModelId = "8", ModelContent = "1acxaa"});
        testDataList.Add(new Model {ModelId = "9", ModelContent = "1acaa"});
        testDataList.Add(new Model {ModelId = "10", ModelContent = "1aaza"});
        testDataList.Add(new Model {ModelId = "11", ModelContent = "1aaca"});
        testDataList.Add(new Model {ModelId = "13", ModelContent = "1aavca"});
        testDataList.Add(new Model {ModelId = "14", ModelContent = "1aaa"});
        testDataList.Add(new Model {ModelId = "15", ModelContent = "1azaa"});
        testDataList.Add(new Model {ModelId = "16", ModelContent = "1acaa"});
        testDataList.Add(new Model {ModelId = "17", ModelContent = "1aacxa"});
        testDataList.Add(new Model {ModelId = "18", ModelContent = "1aaccaa"});
        testDataList.Add(new Model {ModelId = "19", ModelContent = "1a2ccsn5aa"});
        testDataList.Add(new Model {ModelId = "20", ModelContent = "1weaaa"});
    }

    ///<summary>
    /// 传入页返回指定页的数据.我假设每页是显示4条数据的.
    ///</summary>
    ///<param name="page"></param>
    ///<returns></returns>
    public List<Model> GetData(int page)
    {
        return testDataList.Skip(4*(page - 1)).Take(4).ToList();
    }
}

///<summary>
/// 显示用的实体
///</summary>
public class Model
{
    public string ModelId;
    public string ModelContent;
}

<%@ Page Title="主页" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeFile="Default.aspx.cs" Inherits="_Default" %>

<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">

    <asp:Repeater ID="Repeater1" runat="server"  onitemdatabound="Repeater1_ItemDataBound">
        <ItemTemplate>
            <asp:CheckBox ID="CheckBox1" Text='<%# ((Model)Container.DataItem).ModelId%>'  runat="server" />
            <asp:Label ID="Label1" runat="server" Text='<%# ((Model)Container.DataItem).ModelContent%>'></asp:Label>
        </ItemTemplate>
    </asp:Repeater>
    <br/>
    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    <asp:Button ID="Button1" runat="server" onclick="Button1_Click1" 
        Text="Button" />
</asp:Content>