ASP.NET自定义控件入门Demo

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;
using System.ComponentModel;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Security.Permissions;
namespace MyTextBoxControl
{
    [
    AspNetHostingPermission(SecurityAction.Demand,
        Level = AspNetHostingPermissionLevel.Minimal),
    AspNetHostingPermission(SecurityAction.InheritanceDemand,
        Level = AspNetHostingPermissionLevel.Minimal),
    DefaultProperty("Text"),
    ToolboxData("<{0}:MyTextBoxControl runat=\"server\"> </{0}:MyTextBoxControl>")
    ]
    public class MyTextBoxControl : TextBox//继承源生TextBox
    {
        /// <summary>
        /// 为TextBox扩展的Label标签
        /// </summary>
        [
        Bindable(true),
        Category("Appearance"),
        DefaultValue("Label1:"),
        Description("The control content text."),
        Localizable(true)
        ]
        
        public virtual string Label
        {
            get
            {
                string s = (string)ViewState["Label"];
                return (s == null) ? "Label1:" : s;//如果控件Label为空，默认值为"Label1"
            }
            set
            {
                ViewState["Label"] = value;
            }
        }

        /// <summary>
        /// 重绘控件
        /// </summary>
        /// <param name="writer"></param>
        protected override void Render(System.Web.UI.HtmlTextWriter writer)
        {
            System.Web.UI.WebControls.Label lable = new Label();
            lable.ID = "Label1";
            lable.Text = this.Label;//设置标签文本
            lable.Font.Bold = true;//设置文本显示为粗体
            lable.RenderControl(writer);//将Label输出到控件中
            this.Width = Unit.Pixel(255);//设置默认宽度
            this.Text = Guid.NewGuid().ToString("N").ToUpper();//默认文本,设置默认Text值
            this.ReadOnly = true;//设置Text默认只读
            base.Render(writer);//输出控件
        }

    }
}