扩展Label控件(1) - 实现回发(Postback)功能

Label控件既强大又好用。为了让它更强大、更好用，我们来写一个继承自Label的控件。
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扩展Label控件(1) - 实现回发(Postback)功能

作者：webabcd


介绍
扩展Label控件：
通过注册HiddenField控件，使Label控件支持回发(Postback)功能

使用方法（设置属性）：
EnablePostback - 是否启用Label控件的回发(Postback)
HiddenFieldPostfix - 使Label支持回发(Postback)的隐藏控件的后缀名


关键代码
ScriptLibrary.js

//----------------------------
// http://webabcd.cnblogs.com/
//----------------------------

function yy_sl_copyTextToHiddenField(source, destination)
{
/// <summary>将Label控件的的值赋给隐藏控件</summary>

    document.getElementById(destination).value = document.getElementById(source).innerHTML;
}

SmartLabel.cs

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

using System.Web.UI.WebControls;
using System.Web.UI;

[assembly: System.Web.UI.WebResource("YYControls.SmartLabel.Resources.ScriptLibrary.js", "text/javascript")]

namespace YYControls
{
    /**//// <summary>
    /// SmartLabel类，继承自DropDownList
    /// </summary>
    [ToolboxData(@"<{0}:SmartLabel runat='server'></{0}:SmartLabel>")]
    [System.Drawing.ToolboxBitmap(typeof(YYControls.Resources.Icon), "SmartLabel.bmp")]
    public partial class SmartLabel : Label
    {
        /**//// <summary>
        /// 构造函数
        /// </summary>
        public SmartLabel()
        {

        }

        /**//// <summary>
        /// OnPreRender
        /// </summary>
        /// <param name="e">e</param>
        protected override void OnPreRender(EventArgs e)
        {
            base.OnPreRender(e);

            // 实现Label控件的回发(Postback)功能
            ImplementPostback();
        }
    }
}

Property.cs

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

using System.ComponentModel;
using System.Web.UI;

namespace YYControls
{
    /**//// <summary>
    /// SmartLabel类的属性部分
    /// </summary>
    public partial class SmartLabel
    {
        /**//// <summary>
        /// 使Label支持回发(Postback)的隐藏控件的后缀名
        /// </summary>
        [
        Browsable(true),
        Description("使Label支持回发(Postback)的隐藏控件的后缀名"),
        Category("扩展"),
        DefaultValue("EnablePostback")
        ]
        public virtual string HiddenFieldPostfix
        {
            get
            {
                string s = (string)ViewState["HiddenFieldPostfix"];

                return (s == null) ? "EnablePostback" : s;
            }
            set
            {
                ViewState["HiddenFieldPostfix"] = value;
            }
        }

        /**//// <summary>
        /// 是否启用Label控件的回发(Postback)
        /// </summary>
        [
        Browsable(true),
        Description("是否启用Label控件的回发(Postback)"),
        Category("扩展"),
        DefaultValue(false)
        ]
        public virtual bool EnablePostback
        {
            get
            {
                bool? b = (bool?)ViewState["EnablePostback"];

                return (b == null) ? false : (bool)b;
            }

            set
            {
                ViewState["EnablePostback"] = value;
            }
        }
    }
}

EnablePostback.cs

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

using System.Data;
using System.Web.UI.WebControls;
using System.Web.UI;
using System.Web;

namespace YYControls
{
    /**//// <summary>
    /// SmartLabel类的属性部分
    /// </summary>
    public partial class SmartLabel
    {
        /**//// <summary>
        /// 实现Label控件的回发(Postback)功能
        /// </summary>
        private void ImplementPostback()
        {
            if (this.EnablePostback)
            {
                // 使Label支持回发(Postback)的隐藏控件的ID
                string hiddenFieldId = string.Concat(this.ClientID, "_", HiddenFieldPostfix);

                // 注册隐藏控件
                Page.ClientScript.RegisterHiddenField(hiddenFieldId, "");

                // 注册客户端脚本
                this.Page.ClientScript.RegisterClientScriptResource(this.GetType(),
                    "YYControls.SmartLabel.Resources.ScriptLibrary.js");

                // 表单提交前将Label控件的的值赋给隐藏控件
                this.Page.ClientScript.RegisterOnSubmitStatement(this.GetType(),
                    string.Format("yy_sl_enablePostback_{0}",
                        this.ClientID),
                    string.Format("yy_sl_copyTextToHiddenField('{0}', '{1}')",
                        this.ClientID,
                        hiddenFieldId));
            }
        }

        /**//// <summary>
        /// 获取或设置 YYControls.SmartLabel 控件的文本内容
        /// </summary>
        public override string Text
        {
            get
            {
                try
                {
                    if (this.EnablePostback && !string.IsNullOrEmpty(HttpContext.Current.Request[string.Concat(this.ClientID, "_", HiddenFieldPostfix)]))
                    {
                        // 隐藏控件的值
                        return HttpContext.Current.Request[string.Concat(this.ClientID, "_", HiddenFieldPostfix)];
                    }
                    else
                    {
                        return base.Text;
                    }
                }
                catch
                {
                    return base.Text;
                }
            }
            set
            {
                try
                {
                    if (this.EnablePostback && !string.IsNullOrEmpty(HttpContext.Current.Request[string.Concat(this.ClientID, "_", HiddenFieldPostfix)]))
                    {
                        // 隐藏控件的值
                        base.Text = HttpContext.Current.Request[string.Concat(this.ClientID, "_", HiddenFieldPostfix)];
                    }
                    else
                    {
                        base.Text = value;
                    }
                }
                catch
                {
                    base.Text = value;
                }
            }
        }
    }
}

OK
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