[译文]扩展Repeater控件以支持DataPager分页

概述

在网上看到不少的这方面的例子，使Repeater控件象ListView控件一样支持DataPager分页。但是我试了不少，都失败了。所以我就花点时间来自己写了一个。下面是我的解决方案。

代码介绍

首先，我们建立一个用户控件，取名DataPagerRepeater。使其继承自Repeater 并引用System.Web.UI.WebControls.IPageableItemContainer 命名空间。(同时添加System.Web.Extensions引用)并输入以下代码

[ToolboxData("<{0}:DataPagerRepeater runat="server" 
   PersistentDataSource=true></{0}:DataPagerRepeater>")]

public class DataPagerRepeater : Repeater, 
       System.Web.UI.WebControls.IPageableItemContainer, INamingContainer
{

    public int MaximumRows { get { return ViewState["_maximumRows"] != null ? 
                                 (int)ViewState["_maximumRows"] : -1; } }
    public int StartRowIndex { get { return ViewState["_startRowIndex"] != null ? 
                              (int)ViewState["_startRowIndex"] : -1; } }
    public int TotalRows { get { return ViewState["_totalRows"] != null ? 
                               (int)ViewState["_totalRows"] : -1; } }

    public bool PersistentDataSource { 
        get { return ViewState["PersistentDataSource"] != null ? 
              (bool)ViewState["PersistentDataSource"] : true; }
        set { ViewState["PersistentDataSource"] = value; }
    }

    protected override void LoadViewState(object savedState)
    {
        base.LoadViewState(savedState);

        if (Page.IsPostBack)
        {
            if (PersistentDataSource && ViewState["DataSource"] != null)
            {
                this.DataSource = ViewState["DataSource"];
                this.DataBind();
            }
        }
    } 

    public void SetPageProperties(int startRowIndex, int maximumRows, bool databind)
    {
        ViewState["_startRowIndex"] = startRowIndex;
        ViewState["_maximumRows"] = maximumRows;

        if (TotalRows > -1)
        {
            if (TotalRowCountAvailable != null)
            {
                TotalRowCountAvailable(this, 
                   new PageEventArgs((int)ViewState["_startRowIndex"], 
                   (int)ViewState["_maximumRows"], TotalRows));
            }
        }
    }

    protected override void OnDataPropertyChanged()
    { 
        if (MaximumRows != -1)
        {
            this.RequiresDataBinding = true;
        }
        else
            base.OnDataPropertyChanged();
    }

    protected override void RenderChildren(HtmlTextWriter writer)
    {
        if (MaximumRows != -1)
        {
            foreach (RepeaterItem item in this.Items)
            {
                if (item.ItemType == ListItemType.Item || 
                    item.ItemType == ListItemType.AlternatingItem)
                {
                    item.Visible = false;

                    if (item.ItemIndex >= (int)ViewState["_startRowIndex"] && 
                        item.ItemIndex <= ((int)ViewState["_startRowIndex"] + 
                          (int)ViewState["_maximumRows"]))
                    {
                        item.Visible = true;
                    }
                }
                else
                {
                    item.Visible = true;
                }
            }
        }
        base.RenderChildren(writer);
    }

    public override void DataBind()
    { 
        base.DataBind();

        if (MaximumRows != -1)
        {
            int i = 0;
            foreach (object o in GetData())
            {
                i++;
            }
            ViewState["_totalRows"] = i;

            if(PersistentDataSource)
                ViewState["DataSource"] = this.DataSource;
            SetPageProperties(StartRowIndex, MaximumRows, true);
        }
    }

    protected override System.Collections.IEnumerable GetData()
    {
        return base.GetData();
    }

    public event System.EventHandler<PageEventArgs> TotalRowCountAvailable;
}

编译后在asp.net WebForm中使用方法如下：

<cc1:DataPagerRepeater ID="rep1" 
    runat="server" PersistentDataSource="true"> 
<HeaderTemplate > <div></HeaderTemplate> 
<ItemTemplate> 
 <div >
 <%# Eval("Value") %>
 </div>
 </ItemTemplate> 
<FooterTemplate></div></FooterTemplate> 
</cc1:DataPagerRepeater> 

<asp:DataPager ID="DataPager1" 
  PagedControlID="rep1" PageSize="2" runat="server"><Fields><asp:NextPreviousPagerField ButtonType="Button" ShowFirstPageButton="True" 
   ShowNextPageButton="False" ShowPreviousPageButton="False" />

<asp:NumericPagerField /><asp:NextPreviousPagerField ButtonType="Button" ShowLastPageButton="True" 
        ShowNextPageButton="False" ShowPreviousPageButton="False" /></Fields>

</asp:DataPager>

在后台事件中添加以下代码：

protected void Page_Load(object sender, EventArgs e) 
{
    if(!IsPostBack)
    {
        System.Collections.SortedList SL = new System.Collections.SortedList();

        SL.Add("val1","Text1");
        SL.Add("val2","Text2");
        SL.Add("val3","Text3");
        SL.Add("val4","Text4");
        SL.Add("val5","Text5");
        SL.Add("val6","Text6");
        SL.Add("val7","Text7");
        SL.Add("val8","Text8");
        SL.Add("val9","Text9");

        rep1.DataSource = SL;
        rep1.DataBind();
    } 
}

全文完。翻译自CodeProject。