自定义元数据(Attribute)来标识对象(属性，方法，类)

代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Text;
using  System.Reflection;
using  System.Web.UI.WebControls;
using  System.ComponentModel;
using  System.Web.UI;
using  System.Windows.Forms;

namespace  CustomControl
{
     public   class  CustomPropertyControl : WebControl
    {
        System.Web.UI.WebControls.TextBox tb;
         int  intNum  =   0 ;
        [Category( " Appearance " )]
        [NumValidate( 0 ,  10 )]
        [Description( " 输入值范围(0~10) " )]
         public   int  Num
        {
             get
            {
                 return  intNum;
            }
             set
            {
                intNum  =  value;
            }
        }
         protected   override   void  Render(HtmlTextWriter writer)
        {
            Table t  =   new  Table();
            t.CellPadding  =   0 ;
            t.CellSpacing  =   0 ;
            TableRow tr  =   new  TableRow();
            TableCell td_left  =   new  TableCell();
            tb  =   new  System.Web.UI.WebControls.TextBox();
            tb.Text  =   this .intNum.ToString();
            td_left.Controls.Add(tb);
            tr.Controls.Add(td_left);
            NumValidateAttribute numValidateAttribute  =   this .GetNumValidateArribute();
             if  (numValidateAttribute.ValidateResult( this .Num)  ==   false )
            {
                TableCell td_right  =   new  TableCell();
                System.Web.UI.WebControls.Label lb  =   new  System.Web.UI.WebControls.Label();
                lb.ForeColor  =  System.Drawing.Color.Red;
                lb.Text  =   "  值输入范围必须在: "   +  numValidateAttribute.MinValue.
                ToString
                ()  +   " ~ "   +  numValidateAttribute.MaxValue.ToString()  +   " 之间! " ;
                td_right.Controls.Add(lb);
                tr.Controls.Add(td_right);
            }
            t.Controls.Add(tr);
            t.RenderControl(writer);
        }
         private  NumValidateAttribute GetNumValidateArribute()
        {
            System.Type type  =   this .GetType();
            PropertyInfo property  =  type.GetProperty( " Num " );
             object [] attrs  =  ( object [])property.GetCustomAttributes( true );
             foreach  (Attribute attr  in  attrs)
            {
                 if  (attr  is  NumValidateAttribute)
                {
                     return  attr  as  NumValidateAttribute;
                }
            }  return   null ;
        }
    }
    [AttributeUsage(AttributeTargets.Property, AllowMultiple  =   true , Inherited  =   true )]
     public   class  NumValidateAttribute : Attribute
    {
         ///   <summary>
         ///  构造方法
         ///   </summary>
         ///   <param name="intMinValue"> 最小值 </param>
         ///   <param name="intMaxValue"> 最大值 </param>
         public  NumValidateAttribute( int  intMinValue,  int  intMaxValue)
        {
             this .intMinValue  =  intMinValue;
             this .intMaxValue  =  intMaxValue;
        }
         private   int  intMinValue;
         ///   <summary>
         ///  最大值
         ///   </summary>
         public   int  MinValue
        {
             get
            {
                 return  intMinValue;
            }
        }
         private   int  intMaxValue;
         ///   <summary>
         ///  最小值
         ///   </summary>
         public   int  MaxValue
        {
             get
            {
                 return  intMaxValue;
            }
        }
         ///   <summary>
         ///  执行验证
         ///   </summary>
         ///   <param name="value"></param>
         ///   <returns></returns>
         public   bool  ValidateResult( int  value)
        {
             if  ( this .intMinValue  <=  value  &&  value  <=   this .intMaxValue)
            {
                 return   true ;
            }
             else
            {
                 return   false ;
            }
        }
    }
}