Button con disabilitazione dello stesso dopo il click

using System;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Drawing;
namespace AZWebControls
{
    [ToolboxBitmap(typeof(System.Web.UI.WebControls.Button)), DefaultEvent("Click"), DefaultProperty("Text")]
    public class ClickOnceButton : System.Web.UI.WebControls.WebControl, IPostBackEventHandler, IButtonControl
    {
        public event EventHandler Click;
        public event System.Web.UI.WebControls.CommandEventHandler Command;
        private string OnceClickBtnName = "__onceClickBtn";
        [Browsable(true), Category("Behavior")]
        public bool DisableAfterClick
        {
            get
            {
                object o = base.ViewState["DisableAfterClick"];
                return ((o == null) ? false : (bool)o);
            }
            set { base.ViewState["DisableAfterClick"] = value; }
        }
        [Browsable(true), Category("Behavior")]
        public string CommandName
        {
            get
            {
                object o = base.ViewState["CommandName"];
                return ((o == null) ? string.Empty : (string)o);
            }
            set { base.ViewState["CommandName"] = value; }
        }
        [Browsable(true), Category("Behavior")]
        public string CommandArgument
        {
            get
            {
                object o = base.ViewState["CommandArgument"];
                return ((o == null) ? string.Empty : (string)o);
            }
            set { base.ViewState["CommandArgument"] = value; }
        }
        [Browsable(true), Category("Appearance")]
        public string DisabledText
        {
            get
            {
                object o = base.ViewState["DisabledText"];
                return ((o == null) ? string.Empty : (string)o);
            }
            set { base.ViewState["DisabledText"] = value; }
        }
        [Browsable(true), Category("Appearance")]
        public string Text
        {
            get
            {
                object o = base.ViewState["Text"];
                return ((o == null) ? "Button" : (string)o);
            }
            set { base.ViewState["Text"] = value; }
        }
        [Browsable(true), Category("Behavior")]
        public bool CausesValidation
        {
            get
            {
                object o = base.ViewState["CausesValidation"];
                return ((o == null) ? true : (bool)o);
            }
            set { base.ViewState["CausesValidation"] = value; }
        }
        public ClickOnceButton()
            : base(HtmlTextWriterTag.Input)
        {
        }
        [Browsable(false)]
        internal string GetClientValidateEvent
        {
            get {
                if (string.IsNullOrEmpty(this.ValidationGroup))
                    return "if (typeof(Page_ClientValidate) == 'function') Page_ClientValidate(); ";
                else
                    return "if (typeof(Page_ClientValidate) == 'function') Page_ClientValidate('"+this.ValidationGroup+"'); ";
            }
        }
        [Browsable(false)]
        internal string GetClickOnceClientValidateEvent
        {
            get {
                if (string.IsNullOrEmpty(this.ValidationGroup))
                    return "if (typeof(Page_ClientValidate) == 'function') { if(Page_ClientValidate()) { " + GetOnceClickJavascript + " }} else { " + GetOnceClickJavascript + " }";
                else
                    return "if (typeof(Page_ClientValidate) == 'function') { if(Page_ClientValidate('"+this.ValidationGroup+"')) { " + GetOnceClickJavascript + " }} else { " + GetOnceClickJavascript + " }";
            }
        }
        [Browsable(false)]
        internal string GetOnceClickJavascript
        {
            get { return "document.getElementsByName('" + this.OnceClickBtnName + "').item(0).setAttribute('name'," + "this.getAttribute('name')); this.disabled = true; " + (DisabledText == string.Empty ? string.Empty : "this.value = '" + DisabledText + "';") + "this.form.submit();"; }
        }
        protected override void RenderContents(HtmlTextWriter writer)
        {
        }
        protected override void AddAttributesToRender(HtmlTextWriter writer)
        {
            string strOnClick;
            if ((base.Page == null))
            {
                base.Page.VerifyRenderingInServerForm(this);
            }
            writer.AddAttribute(HtmlTextWriterAttribute.Type, "submit");
            writer.AddAttribute(HtmlTextWriterAttribute.Name, base.UniqueID);
            writer.AddAttribute(HtmlTextWriterAttribute.Value, this.Text);
            if ((base.Page != null) & this.CausesValidation & base.Page.Validators.Count > 0)
            {
                if (this.DisableAfterClick)
                {
                    strOnClick = this.GetClickOnceClientValidateEvent;
                }
                else
                {
                    strOnClick = this.GetClientValidateEvent;
                }
                if (base.Attributes.Count > 0 & (base.Attributes["onclick"] != null))
                {
                    strOnClick = string.Concat(base.Attributes["onclick"], strOnClick);
                    base.Attributes.Remove("onclick");
                }
                writer.AddAttribute("language", "javascript");
                writer.AddAttribute(HtmlTextWriterAttribute.Onclick, strOnClick);
            }
            else if (DisableAfterClick == true)
            {
                strOnClick = GetOnceClickJavascript;
                if (base.Attributes.Count > 0 & (base.Attributes["onclick"] != null))
                {
                    strOnClick = string.Concat(base.Attributes["onclick"], strOnClick);
                    base.Attributes.Remove("onclick");
                }
                writer.AddAttribute("language", "javascript");
                writer.AddAttribute(HtmlTextWriterAttribute.Onclick, strOnClick);
            }
            base.AddAttributesToRender(writer);
        }
        protected override void OnInit(EventArgs e)
        {
            if (DisableAfterClick && !IsHiddenFieldRegistered())
            {
                base.Page.ClientScript.RegisterHiddenField(this.OnceClickBtnName, "");
                //base.Page.RegisterHiddenField(this.OnceClickBtnName, "");
            }
            base.OnInit(e);
        }
        private bool IsHiddenFieldRegistered()
        {
            foreach (Control ctl in base.Page.Controls)
            {
                if (ctl is HtmlInputHidden)
                {
                    if (ctl.ID == this.OnceClickBtnName)
                    {
                        return true;
                    }
                }
            }
            return false;
        }
        protected virtual void OnClick(EventArgs e)
        {
            if (Click != null)
            {
                Click(this, e);
            }
        }
        protected virtual void OnCommand(System.Web.UI.WebControls.CommandEventArgs e)
        {
            if (Command != null)
            {
                Command(this, e);
            }
        }
        void System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(string eventArgument)
        {
            if (this.CausesValidation)
            {
                base.Page.Validate();
            }
            this.OnClick(new EventArgs());
            this.OnCommand(new System.Web.UI.WebControls.CommandEventArgs(this.CommandName, this.CommandArgument));
        }
        #region IButtonControl Members
        [UrlProperty("*.aspx"), Editor("System.Web.UI.Design.UrlEditor, System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", typeof(System.Drawing.Design.UITypeEditor)), Themeable(false), DefaultValue("")]
        public virtual string PostBackUrl
        {
            get
            {
                string str = (string)this.ViewState["PostBackUrl"];
                if (str != null)
                {
                    return str;
                }
                return string.Empty;
            }
            set
            {
                this.ViewState["PostBackUrl"] = value;
            }
        }
        [DefaultValue(""), Themeable(false)]
        public virtual string ValidationGroup
        {
            get
            {
                string str = (string)this.ViewState["ValidationGroup"];
                if (str != null)
                {
                    return str;
                }
                return string.Empty;
            }
            set
            {
                this.ViewState["ValidationGroup"] = value;
            }
        }
        #endregion
    }
}