简单的asp.net自定义控件

新建一个类，命名为YearAndMonthInput
代码如下：

using Forks.EnterpriseServices.DomainObjects2.DQuery;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web.UI;
using System.Web.UI.WebControls;
using TSingSoft.WebControls2;

namespace BWP.Web.Pages.B3PigSelfBreed.Reports.CompanySettlementSummary_
{
  //继承INamingContainer接口使状态保持，防止页面刷新后控件值清空
  class YearAndMonthInput:Control,INamingContainer
  {
    //是否允许输入为空
    bool _allowNull = false;
    public bool AllowNull
    {
      get { return _allowNull; }
      set { _allowNull = value; }
    }
    //使用static防止每次页面加载都进行数据更新
    static TextBox txt_Year=new TextBox();
    static TextBox txt_Month=new TextBox();
    Label lb_Year;
    Label lb_Month;
    protected override void CreateChildControls()
    {
      base.CreateChildControls();
      //添加年和月的输入框以及文本控件
      //txt_Year = new TextBox();
      txt_Year.Width = 30;
      if (txt_Year.Text == "")
      {
        txt_Year.Text = DateTime.Now.Year.ToString();
      }
      Controls.Add(txt_Year);
      lb_Year = new Label();
      lb_Year.Text = "年";
      Controls.Add(lb_Year);
      //txt_Month = new TextBox();
      txt_Month.Width = 30;
      if (txt_Month.Text == "")
      {
        txt_Month.Text = DateTime.Now.Month.ToString();
      }
      Controls.Add(txt_Month);
      lb_Month = new Label();
      lb_Month.Text = "月";
      Controls.Add(lb_Month);
    }

    /// <summary>
    /// 通过输入年月变成该年月的第一天
    /// </summary>
    /// <returns></returns>
    DateTime? GetValue()
    {
      EnsureChildControls();
      if (!string.IsNullOrEmpty(txt_Year.Text) && !string.IsNullOrEmpty(txt_Month.Text))
      {
        int year = 0;
        int month = 0;
        if (int.TryParse(txt_Year.Text, out year) && int.TryParse(txt_Month.Text, out month))
        {
          if (year <= DateTime.Now.Year && (month > 0 && month < 13))
          {
            return new DateTime(year, month, 1);
          }
          else
          {
            throw new Exception("输入年份不能大于今年，输入月份必须在1-12之间！");
          }
        }
        else
        {
          throw new Exception("请输入数字！");
        }
      }
      else
      {
        if (!_allowNull)
        {
          throw new Exception("输入的年月不能为空！");
        }
      }
      return null;
    }

    /// <summary>
    /// 进行的操作
    /// </summary>
    /// <param name="query"></param>
    /// <param name="dateExpression"></param>
    public void AddConditions()
    {
      //随意
    }
  }
}