自定义Attribute简例

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

namespace WebComTest
{
    [DefaultProperty("Num")]
    [ToolboxData("<{0}:CustomPropertyControl runat=server></{0}:CustomPropertyControl>")]
    public class CustomPropertyControl : WebControl
    {
        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 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();
                Label lb = new 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();//这里可根据需求修改。this可改为其它类
            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;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace WebComTest
{
    [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;
            }
        }
    }
}