simplepager.cs

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using System;
using System.Collections;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace BookShop.Web.Controls {
	public class SimplePager : Repeater {

		//Static constants
		protected const string HTML1 = "<table cellpadding=0 cellspacing=0><tr><td colspan=2>";
		protected const string HTML2 = "</td></tr><tr class=gridNav><td>";
		protected const string HTML3 = "</td><td align=right>";
		protected const string HTML4 = "</td></tr></table>";
		private static readonly Regex RX = new Regex(@"^&page=\d+", RegexOptions.Compiled);
		private const string LINK_PREV = "<a href=?page={0}><img src=Images/buttonPrev.gif alt=Previous border=\"0\"></a>";
		private const string LINK_MORE = "<a href=?page={0}><img src=Images/buttonMore.gif alt=More border=\"0\"></a>";
		private const string KEY_PAGE = "page";
		private const string COMMA = "?";
		private const string AMP = "&";

		protected string emptyText;
		private IList dataSource;
		private int pageSize = 10;
		private int currentPageIndex;
		private int itemCount;
		
		override public object DataSource {
			set {
				//This try catch block is to avoid issues with the VS.NET designer
				//The designer will try and bind a datasource which does not derive from ILIST
				try{
					dataSource = (IList)value;
					ItemCount = dataSource.Count;
				}catch{
					dataSource = null;
					ItemCount = 0;
				}
			}
		}

		public int PageSize {
			get { return pageSize; }
			set { pageSize = value; }
		}

		protected int PageCount {
			get { return (ItemCount - 1) / pageSize; }
		}

		virtual protected int ItemCount {
			get { return itemCount; }
			set { itemCount = value; }
		}

		virtual public int CurrentPageIndex {
			get { return currentPageIndex; }
			set { currentPageIndex = value; }
		}

		public string EmptyText {
			set { emptyText = value; }
		}

		public void SetPage(int index) {
			OnPageIndexChanged(new DataGridPageChangedEventArgs(null, index));
		}

		override protected void OnLoad(EventArgs e) {
			if (Visible) {
				string page = Context.Request[KEY_PAGE];
				int index = (page != null) ? int.Parse(page) : 0;
				SetPage(index);
			}
		}


		/// <summary>
		/// Overriden method to control how the page is rendered
		/// </summary>
		/// <param name="writer"></param>
		override protected void Render(HtmlTextWriter writer) {
			
			//Check there is some data attached
			if (ItemCount == 0) {
				writer.Write(emptyText);
				return;
			}

			//Mask the query
			string query = Context.Request.Url.Query.Replace(COMMA, AMP);
			query = RX.Replace(query, string.Empty);

			// Write out the first part of the control, the table header
			writer.Write(HTML1);
			
			// Call the inherited method
			base.Render(writer);

			// Write out a table row closure
			writer.Write(HTML2);
			
			//Determin whether next and previous buttons are required
			//Previous button?
			if (currentPageIndex > 0)
				writer.Write(string.Format(LINK_PREV, (currentPageIndex - 1) + query));

			//Close the table data tag
			writer.Write(HTML3);

			//Next button?
			if (currentPageIndex < PageCount)
				writer.Write(string.Format(LINK_MORE, (currentPageIndex + 1) + query));

			//Close the table
			writer.Write(HTML4);
		}

		override protected void OnDataBinding(EventArgs e) {

			//Work out which items we want to render to the page
			int start = CurrentPageIndex * pageSize;
			int size = Math.Min(pageSize, ItemCount - start);
	
			IList page = new ArrayList();

			//Add the relevant items from the datasource
			for (int i = 0; i < size; i++)
				page.Add(dataSource[start + i]);
			
			//set the base objects datasource
			base.DataSource = page;			
			base.OnDataBinding(e);
			
		}

		public event DataGridPageChangedEventHandler PageIndexChanged;

		virtual protected void OnPageIndexChanged(DataGridPageChangedEventArgs e) {
			if (PageIndexChanged != null)
				PageIndexChanged(this, e);
		}
	}
}