用C#写一个Web自定义控件

原来写的用户控件，但是维护太麻烦，后来就写了一个自定义控件，比较好维护，使用也方便多了。
该控件是一个时间控件，通过下拉列表框选择时间的年、月、日、时、分、秒。初始化时要提供可选时间的
起始年份。

源代码如下：

using System;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
using System.ComponentModel.Design;

namespace UserTime
{
 ///

 /// 用户自定义时间控件，取到年、月、日、时、分、秒
 ///

 [DefaultProperty("Text"),
  ToolboxData("<{0}:clsUserTime runat=server>")]
 //INamingContainer为子控件提供了一个新的命名范围,保证子控件的ID唯一性
 public class clsUserTime : System.Web.UI.WebControls.WebControl, INamingContainer
 {
  private System.Web.UI.WebControls.DropDownList ddlYear;
  private DropDownList ddlMonth;
  private DropDownList ddlDay;
  private DropDownList ddlHour;
  private DropDownList ddlMinite;
  private DropDownList ddlSecond;

  private static int beginYear = 0;     //起始年号，这里必须使用static以防二次调用后变量被清零
  private static bool IsInit = false;   //是否已经初始化过，这里必须使用static以防二次调用后变量被清零

  public int Year  //取控件时间：年
  {
   get
   {
    return ddlYear.SelectedIndex + beginYear;
   }
  }

  public int Month  //取控件时间：月
  {
   get
   {
    return ddlMonth.SelectedIndex + 1;
   }
  }

  public int Day   //取控件时间：日
  {
   get
   {
    return ddlDay.SelectedIndex + 1;
   }
  }

  public int Hour  //取控件时间：时
  {
   get
   {
    return ddlHour.SelectedIndex;
   }
  }

  public int Minite  //取控件时间：分
  {
   get
   {
    return ddlMinite.SelectedIndex;
   }
  }

  public int Second   //取控件时间：秒
  {
   get
   {
    return ddlSecond.SelectedIndex;
   }
  }

  //用起始年号初始化控件，如果已经初始化过控件，直接返回
  public void InitControls(int startYear, int endYear)
  {
   if (IsInit)
   {
    return;
   }
   EnsureChildControls();
   if (startYear > endYear)
   {
    int tmp = startYear;
    startYear = endYear;
    endYear = startYear;
   }
   beginYear = startYear;
   for (int i = startYear; i <= endYear; ++i)
   {
    ddlYear.Items.Add(i.ToString());
   }
   for (int i = 1; i <=12; ++i)
   {
    ddlMonth.Items.Add(i.ToString());
   }
   for (int i = 1; i <= 31; ++i)
   {
    ddlDay.Items.Add(i.ToString());
   }
   for (int i = 0; i < 24; ++i)
   {
    ddlHour.Items.Add(i.ToString());
   }
   for (int i = 0; i < 60; ++i)
   {
    ddlMinite.Items.Add(i.ToString());
    ddlSecond.Items.Add(i.ToString());
   }
   IsInit = true;
  }
  //重载Controls属性，取得ControlCollection对象，该对象表示UI层次结构中的服务器控件的子控件
  public override ControlCollection Controls
  {
   get
   {
    //确定服务器是否包含子控件
    EnsureChildControls();
    return base.Controls;
   }
  }

  //动态创建子控件
  protected override void CreateChildControls()
  {
   //创建年、月、日、时、分、秒下拉列表框
   this.Controls.Clear();
   ddlYear = new DropDownList();
   ddlYear.ID = "ddlYear";
   ddlYear.Width = 54;

   ddlMonth = new DropDownList();
   ddlMonth.ID = "ddlMonth";
   ddlMonth.Width = 40;

   ddlDay = new DropDownList();
   ddlDay.ID = "ddlDay";
   ddlDay.Width = 40;

   ddlHour = new DropDownList();
   ddlHour.ID = "ddlHour";
   ddlHour.Width = 40;
           
   ddlMinite = new DropDownList();
   ddlMinite.ID = "ddlMinite";
   ddlMinite.Width = 40;

   ddlSecond = new DropDownList();
   ddlSecond.ID = "ddlSecond";
   ddlSecond.Width = 40;

   this.Controls.Add(ddlYear);
   this.Controls.Add(ddlMonth);
   this.Controls.Add(ddlDay);
   this.Controls.Add(ddlHour);
   this.Controls.Add(ddlMinite);
   this.Controls.Add(ddlSecond);

   base.CreateChildControls ();
  }

  ///

  /// 将此控件呈现给指定的输出参数。
  ///

  /// 要写出到的 HTML 编写器
  protected override void Render(HtmlTextWriter output)
  {
   //将要呈现的HTML属性添加到指定的System.Web.HtmlTextWriter中
   AddAttributesToRender(output);
   output.AddAttribute(System.Web.UI.HtmlTextWriterAttribute.Cellpadding, "0", false);

   //制定一个表，把子控件排在一行上
   output.RenderBeginTag(HtmlTextWriterTag.Table);  //表
   output.RenderBeginTag(HtmlTextWriterTag.Tr);     //行

   //年下拉列表框
   output.RenderBeginTag(HtmlTextWriterTag.Td);     //列
   ddlYear.RenderControl(output);
   output.RenderEndTag();

   output.RenderBeginTag(HtmlTextWriterTag.Td);
   output.Write("年");
   output.RenderEndTag();

   //月下拉列表框
   output.RenderBeginTag(HtmlTextWriterTag.Td);
   ddlMonth.RenderControl(output);
   output.RenderEndTag();

   output.RenderBeginTag(HtmlTextWriterTag.Td);
   output.Write("月");
   output.RenderEndTag();

   //日下拉列表框
   output.RenderBeginTag(HtmlTextWriterTag.Td);
   ddlDay.RenderControl(output);
   output.RenderEndTag();

   output.RenderBeginTag(HtmlTextWriterTag.Td);
   output.Write("日");
   output.RenderEndTag();

   //时下拉列表框
   output.RenderBeginTag(HtmlTextWriterTag.Td);
   ddlHour.RenderControl(output);
   output.RenderEndTag();

   output.RenderBeginTag(HtmlTextWriterTag.Td);
   output.Write("时");
   output.RenderEndTag();

   //分下拉列表框
   output.RenderBeginTag(HtmlTextWriterTag.Td);
   ddlMinite.RenderControl(output);
   output.RenderEndTag();

   output.RenderBeginTag(HtmlTextWriterTag.Td);
   output.Write("分");
   output.RenderEndTag();

   //秒下拉列表框
   output.RenderBeginTag(HtmlTextWriterTag.Td);
   ddlSecond.RenderControl(output);
   output.RenderEndTag();

   output.RenderBeginTag(HtmlTextWriterTag.Td);
   output.Write("秒");
   output.RenderEndTag();

   output.RenderEndTag();
   output.RenderEndTag();
  }

  public DateTime GetTime() //取得选定的时间
  {
   DateTime time = new DateTime(this.Year, this.Month, this.Day, this.Hour, this.Minite, this.Second, 0);
   return time;
  }

  //清除控件里所有下拉列表框的值
  public void ClearControls()
  {
   ddlYear.Items.Clear();
   ddlMonth.Items.Clear();
   ddlDay.Items.Clear();
   ddlHour.Items.Clear();
   ddlMinite.Items.Clear();
   ddlSecond.Items.Clear();
   IsInit = false;
  }

  //撤消对所有下拉列表框的选项
  public void ClearSelection()
  {
   ddlYear.ClearSelection();
   ddlMonth.ClearSelection();
   ddlDay.ClearSelection();
   ddlHour.ClearSelection();
   ddlMinite.ClearSelection();
   ddlSecond.ClearSelection();
  }
 }
}