自制Web控件－分页导航器

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

namespace CustomWebControl.PageNavigation
{
    [System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand, Name = "FullTrust")]
    public class PageNavigation : WebControl, IPostBackDataHandler, IPostBackEventHandler
    {
        public const string PAGE_CURRENT = "pageCurrent";
        public const string PAGE_SUM = "pageSum";
        public const string CSS_CLASS = "cssClass";
        public const string SEARCH_STATE = "searchState";

        [Bindable(true), Category("数据"), DefaultValue(1), Description("当前页码")]
        public int PageCurrent
        {
            get
            {
                int pageCurrent = null == ViewState[PAGE_CURRENT] ? 1 : (int)ViewState[PAGE_CURRENT];
                return pageCurrent;
            }
            set
            {
                ViewState[PAGE_CURRENT] = value;
            }
        }

        [Bindable(true), Category("数据"), DefaultValue(0), Description("总页数")]
        public int PageSum
        {
            get
            {
                int pageSum = null == ViewState[PAGE_SUM] ? 0 : (int)ViewState[PAGE_SUM];
                return pageSum;
            }
            set
            {
                ViewState[PAGE_SUM] = value;
            }
        }

        [Bindable(true), Category("外观"), DefaultValue(""), Description("Css Class名称")]
        public override string CssClass
        {
            get
            {
                string str = null == ViewState[CSS_CLASS] ? string.Empty : ViewState[CSS_CLASS].ToString();
                return str;
            }
            set
            {
                ViewState[CSS_CLASS] = value;
            }
        }

        //事件键定义
        private static readonly object _event = new object();

        /// <summary>
        /// 当前页改变事件
        /// </summary>
        [Category("事件"), Description("当前页码改变时触发此事件")]
        public event EventHandler ChangePageCurrent
        {
            add
            {
                Events.AddHandler(_event, value);
            }
            remove
            {
                Events.RemoveHandler(_event, value);
            }
        }

        /// <summary>
        /// 当前页改变的事件方法
        /// </summary>
        /// <param name="e"></param>
        protected virtual void OnChangePageCurrent(EventArgs e)
        {
            EventHandler handler = (EventHandler)Events[_event];

            if (handler != null)
            {
                handler(this, e);
            }
        }

        protected override void RenderContents(HtmlTextWriter output)
        {
            if (this.PageSum != 0 && this.PageCurrent > this.PageSum)
                this.PageCurrent = this.PageSum;
            if (this.PageSum != 0 && this.PageCurrent < 1)
                this.PageCurrent = 1;

            output.AddAttribute(HtmlTextWriterAttribute.Width, "100%");
            output.AddAttribute(HtmlTextWriterAttribute.Height, "30");
            output.AddAttribute(HtmlTextWriterAttribute.Border, "0");
            output.AddAttribute(HtmlTextWriterAttribute.Cellpadding, "0");
            output.AddAttribute(HtmlTextWriterAttribute.Cellspacing, "0");
            output.AddAttribute(HtmlTextWriterAttribute.Class, this.CssClass);
            output.RenderBeginTag(HtmlTextWriterTag.Table);
            output.RenderBeginTag(HtmlTextWriterTag.Tr);
            output.RenderBeginTag(HtmlTextWriterTag.Td);
            output.AddAttribute(HtmlTextWriterAttribute.Align, "right");
            output.RenderBeginTag(HtmlTextWriterTag.Div);
            output.AddStyleAttribute(HtmlTextWriterStyle.Cursor, "pointer");
            output.AddStyleAttribute(HtmlTextWriterStyle.TextDecoration, "underline");
            if (this.PageCurrent == 1 || this.PageSum == 0)
                output.AddAttribute(HtmlTextWriterAttribute.Disabled, "disabled");
            else
                output.AddAttribute(HtmlTextWriterAttribute.Onclick, Page.ClientScript.GetPostBackEventReference(this, "First"));
            output.RenderBeginTag(HtmlTextWriterTag.Span);
            output.Write("首&nbsp;&nbsp;页");
            output.RenderEndTag();
            output.Write("&nbsp;&nbsp;");
            output.AddStyleAttribute(HtmlTextWriterStyle.Cursor, "pointer");
            output.AddStyleAttribute(HtmlTextWriterStyle.TextDecoration, "underline");
            if (this.PageCurrent == 1 || this.PageSum == 0)
                output.AddAttribute(HtmlTextWriterAttribute.Disabled, "disabled");
            else
                output.AddAttribute(HtmlTextWriterAttribute.Onclick, Page.ClientScript.GetPostBackEventReference(this, "Previous"));
            output.RenderBeginTag(HtmlTextWriterTag.Span);
            output.Write("上&nbsp;&nbsp;页");
            output.RenderEndTag();
            output.Write("&nbsp;&nbsp;");
            output.AddStyleAttribute(HtmlTextWriterStyle.Cursor, "pointer");
            output.AddStyleAttribute(HtmlTextWriterStyle.TextDecoration, "underline");
            if (this.PageCurrent == this.PageSum || this.PageSum == 0)
                output.AddAttribute(HtmlTextWriterAttribute.Disabled, "disabled");
            else
                output.AddAttribute(HtmlTextWriterAttribute.Onclick, Page.ClientScript.GetPostBackEventReference(this, "Next"));
            output.RenderBeginTag(HtmlTextWriterTag.Span);
            output.Write("下&nbsp;&nbsp;页");
            output.RenderEndTag();
            output.Write("&nbsp;&nbsp;");
            output.AddStyleAttribute(HtmlTextWriterStyle.Cursor, "pointer");
            output.AddStyleAttribute(HtmlTextWriterStyle.TextDecoration, "underline");
            if (this.PageCurrent == this.PageSum || this.PageSum == 0)
                output.AddAttribute(HtmlTextWriterAttribute.Disabled, "disabled");
            else
                output.AddAttribute(HtmlTextWriterAttribute.Onclick, Page.ClientScript.GetPostBackEventReference(this, "Last"));
            output.RenderBeginTag(HtmlTextWriterTag.Span);
            output.Write("尾&nbsp;&nbsp;页");
            output.RenderEndTag();
            output.Write("&nbsp;&nbsp;");
            output.RenderBeginTag(HtmlTextWriterTag.Span);
            output.Write("页&nbsp;&nbsp;码:" + (this.PageSum==0?"0":this.PageCurrent.ToString()) + "/" + this.PageSum.ToString() + "&nbsp;&nbsp;转&nbsp;&nbsp;到:");
            output.RenderEndTag();
            output.AddAttribute(HtmlTextWriterAttribute.Onchange,Page.ClientScript.GetPostBackEventReference(this, "Go"));
            output.AddAttribute(HtmlTextWriterAttribute.Id, this.UniqueID);
            output.AddAttribute(HtmlTextWriterAttribute.Name, this.UniqueID);
            output.RenderBeginTag(HtmlTextWriterTag.Select);
            for (int i = 1; i <= this.PageSum; i++)
            {
                if (i != this.PageCurrent)
                    output.Write("<option value=\"" + i.ToString() + "\">" + i.ToString() + "</option>");
                else
                    output.Write("<option value=\"" + i.ToString() + "\" selected=\"selected\">" + i.ToString() + "</option>");
            }
            output.AddAttribute(HtmlTextWriterAttribute.Onchange, Page.ClientScript.GetPostBackEventReference(this, "pageCurrent"));
            output.RenderEndTag();
            output.Write("&nbsp;&nbsp;");
            output.RenderEndTag();
            output.RenderEndTag();
            output.RenderEndTag();
            output.RenderEndTag();
        }

        protected override void Render(HtmlTextWriter writer)
        {
            if (Page != null)
            {
                Page.VerifyRenderingInServerForm(this);
            }

            base.Render(writer);
        }

        void IPostBackEventHandler.RaisePostBackEvent(string eventArgument)
        {
            switch (eventArgument)
            {
                case "First":
                    if (this.PageCurrent == 1)
                        return;
                    this.PageCurrent = 1;
                    OnChangePageCurrent(EventArgs.Empty);
                    break;
                case "Previous":
                    if (this.PageCurrent > 1)
                        this.PageCurrent = this.PageCurrent - 1;
                    else
                        return;
                    OnChangePageCurrent(EventArgs.Empty);
                    break;
                case "Next":
                    if (this.PageCurrent < this.PageSum)
                        this.PageCurrent = this.PageCurrent + 1;
                    else
                        return;
                    OnChangePageCurrent(EventArgs.Empty);
                    break;
                case "Last":
                    if (this.PageCurrent == this.PageSum)
                        return;
                    this.PageCurrent = this.PageSum;
                    OnChangePageCurrent(EventArgs.Empty);
                    break;
                case "Go":
                    OnChangePageCurrent(EventArgs.Empty);
                    break;
            }
        }

        public bool LoadPostData(string postDataKey, System.Collections.Specialized.NameValueCollection postCollection)
        {
            int pageCurrentValue = PageCurrent;

            int pageCurrentPostedValue = int.Parse(postCollection[postDataKey]);

            if (pageCurrentValue != pageCurrentPostedValue)
            {
                this.PageCurrent = pageCurrentPostedValue;
                return true;
            }

            return false;
        }

        public void RaisePostDataChangedEvent()
        {
       
        }
    }
}