创建富中继器，DataBind清除自定义添加的控件

Question

So...I had this clever idea that I'd create my own Repeater control that implements paging and sorting by inheriting from Repeater and extending it's capabilities. I found some information and bits and pieces on how to go about this and everything seemed ok...

I created a WebControlLibrary to house my custom controls. Along with the enriched repeater, I created a composite control that would act as the "pager bar", having forward, back and page selection. My pager bar works 100% on it's own, properly firing a paged changed event when the user interacts with it. The rich repeater databinds without issue, but when the databind fires (when I call base.databind()), the control collection is cleared out and my pager bars are removed. This screws up the viewstate for the pager bars making them unable to fire their events properly or maintain their state.

I've tried adding the controls back to the collection after base.databind() fires, but that doesn't solve the issue. I start to get very strange results including problems with altering the hierarchy of the control tree (resolved by adding [ViewStateModeById]).

Before I go back to the drawing board and create a second composite control which contains a repeater and the pager bars (so that the repeater isn't responsible for the pager bars viewstate) are there any thoughts about how to resolve the issue?

In the interest of share and share alike, the code for the repeater itself is below, the pagerbars aren't as significant as the issue is really the maintaining of state for any additional child controls. (forgive the roughness of some of the code...it's still a work in progress)

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.Data;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

[ViewStateModeById]
public class SortablePagedRepeater : Repeater, INamingContainer {

    private SuperRepeaterPagerBar topBar = new SuperRepeaterPagerBar();
    private SuperRepeaterPagerBar btmBar = new SuperRepeaterPagerBar();

    protected override void OnInit(EventArgs e) {
        Page.RegisterRequiresControlState(this);

        InitializeControls();
        base.OnInit(e);
        EnsureChildControls();
    }

    protected void InitializeControls() {
        topBar.ID = this.ID + "__topPagerBar";
        topBar.NumberOfPages = this._currentProperties.numOfPages;
        topBar.CurrentPage = this.CurrentPageNumber;
        topBar.PageChanged +=
            new SuperRepeaterPagerBar.PageChangedEventHandler(PageChanged);

        btmBar.ID = this.ID + "__btmPagerBar";
        btmBar.NumberOfPages = this._currentProperties.numOfPages;
        btmBar.CurrentPage = this.CurrentPageNumber;
        btmBar.PageChanged +=
            new SuperRepeaterPagerBar.PageChangedEventHandler(PageChanged);
    }

    protected override void CreateChildControls() {
        EnsureDataBound();

        this.Controls.Add(topBar);
        this.Controls.Add(btmBar);
        //base.CreateChildControls();
    }

    private void PageChanged(object sender, int newPage) {
        this.CurrentPageNumber = newPage;
    }

    public override void DataBind() {
        //pageDataSource();

        //DataBind removes all controls from control collection...
        base.DataBind();
        Controls.Add(topBar);
        Controls.Add(btmBar);
    }

    private void pageDataSource() {
        //Create paged data source
        PagedDataSource pds = new PagedDataSource();

        pds.PageSize = this.ItemsPerPage;
        pds.AllowPaging = true;

        // first get a PagedDataSource going and perform sort if possible...
        if (base.DataSource is System.Collections.IEnumerable) {
            pds.DataSource = (System.Collections.IEnumerable)base.DataSource;
        } else if (base.DataSource is System.Data.DataView) {
            DataView data = (DataView)DataSource;
            if (this.SortBy != null && data.Table.Columns.Contains(this.SortBy)) {
                data.Sort = this.SortBy;
            }
            pds.DataSource = data.Table.Rows;
        } else if (base.DataSource is System.Data.DataTable) {
            DataTable data = (DataTable)DataSource;
            if (this.SortBy != null && data.Columns.Contains(this.SortBy)) {
                data.DefaultView.Sort = this.SortBy;
            }
            pds.DataSource = data.DefaultView;
        } else if (base.DataSource is System.Data.DataSet) {
            DataSet data = (DataSet)DataSource;
            if (base.DataMember != null && data.Tables.Contains(base.DataMember)) {
                if (this.SortBy != null && data.Tables[base.DataMember].Columns.Contains(this.SortBy)) {
                    data.Tables[base.DataMember].DefaultView.Sort = this.SortBy;
                }
                pds.DataSource = data.Tables[base.DataMember].DefaultView;
            } else if (data.Tables.Count > 0) {
                if (this.SortBy != null && data.Tables[0].Columns.Contains(this.SortBy)) {
                    data.Tables[0].DefaultView.Sort = this.SortBy;
                }
                pds.DataSource = data.Tables[0].DefaultView;
            } else {
                throw new Exception("DataSet doesn't have any tables.");
            }
        } else if (base.DataSource == null) {
            // don't do anything?
        } else {
            throw new Exception("DataSource must be of type System.Collections.IEnumerable.  The DataSource you provided is of type " + base.DataSource.GetType().ToString());
        }


        if (pds != null && base.DataSource != null) {
            //Make sure that the page doesn't exceed the maximum number of pages 
            //available
            if (this.CurrentPageNumber >= pds.PageCount) {
                this.CurrentPageNumber = pds.PageCount - 1;
            }

            //Set up paging values...
            btmBar.CurrentPage = topBar.CurrentPage = pds.CurrentPageIndex = this.CurrentPageNumber;
            this._currentProperties.numOfPages = btmBar.NumberOfPages = topBar.NumberOfPages = pds.PageCount;

            base.DataSource = pds;
        }
    }

    public override object DataSource {
        get {
            return base.DataSource;
        }
        set {
            //init();  //reset paging/sorting values since we've potentially changed data sources.
            base.DataSource = value;
            pageDataSource();
        }
    }

    protected override void Render(HtmlTextWriter writer) {
        topBar.RenderControl(writer);
        base.Render(writer);
        btmBar.RenderControl(writer);
    }

    [Serializable]
    protected struct CurrentProperties {
        public int pageNum;
        public int itemsPerPage;
        public int numOfPages;
        public string sortBy;
        public bool sortDir;
    }

    protected CurrentProperties _currentProperties = new CurrentProperties();

    protected override object SaveControlState() {
        return this._currentProperties;
    }

    protected override void LoadControlState(object savedState) {
        this._currentProperties = (CurrentProperties)savedState;
    }

    [Category("Status")]
    [Browsable(true)]
    [NotifyParentProperty(true)]
    [DefaultValue("")]
    [Localizable(false)]
    public string SortBy {
        get { return this._currentProperties.sortBy; }
        set {
            //If sorting by the same column, swap the sort direction.
            if (this._currentProperties.sortBy == value) {
                this.SortAscending = !this.SortAscending;
            } else {
                this.SortAscending = true;
            }
            this._currentProperties.sortBy = value;
        }
    }

    [Category("Status")]
    [Browsable(true)]
    [NotifyParentProperty(true)]
    [DefaultValue(true)]
    [Localizable(false)]
    public bool SortAscending {
        get { return this._currentProperties.sortDir; }
        set { this._currentProperties.sortDir = value; }
    }

    [Category("Status")]
    [Browsable(true)]
    [NotifyParentProperty(true)]
    [DefaultValue(25)]
    [Localizable(false)]
    public int ItemsPerPage {
        get { return this._currentProperties.itemsPerPage; }
        set { this._currentProperties.itemsPerPage = value; }
    }

    [Category("Status")]
    [Browsable(true)]
    [NotifyParentProperty(true)]
    [DefaultValue(1)]
    [Localizable(false)]
    public int CurrentPageNumber {
        get { return this._currentProperties.pageNum; }
        set { 
            this._currentProperties.pageNum = value;
            pageDataSource();
        }
    }
}

Answer 1

您还可以使用新的ASP.NET ListView控件 （自.Net 3.5起），它具有分页/排序数据绑定和模板，这意味着您可以将其用作转发器，也可以非常轻松地完成诸如网格之类的复杂工作，例如带有内联编辑的显示。