basepostbackcontrol.cs

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//------------------------------------------------------------------------------
// Copyright (c) 2000-2003 Microsoft Corporation. All Rights Reserved.
//------------------------------------------------------------------------------

namespace Microsoft.Web.UI.WebControls
{
    using System;
    using System.Web.UI;
    using System.Collections.Specialized;

    /// <summary>
    /// Implements the IPostBackEventHandler and IPostBackDataHandler interfaces.
    /// Creates a hidden helper, if needed, and allows controls to set and receive
    /// the data from that helper.
    /// 
    /// Implementation Notes:
    /// 1. Be sure to assign the data to HelperData either before
    ///    OnPreRender or in OnPreRender before calling base.OnPreRender().
    /// 2. The hidden helper will have an ID of HelperID.
    /// 3. The hidden helper will only be created when NeedHelper is true.
    /// </summary>
    public abstract class BasePostBackControl : BaseRichControl, IPostBackEventHandler, IPostBackDataHandler
    {
        private string _szHelperID;
        private string _szHelperData = String.Empty;

        /// <summary>
        /// Processes post back data for the server control given the data from the hidden helper.
        /// </summary>
        /// <param name="szData">The data from the hidden helper</param>
        /// <returns>true if the server control's state changes as a result of the post back; otherwise false.</returns>
        protected virtual bool ProcessData(string szData)
        {
            return false;
        }

        /// <summary>
        /// Processes post back data for a server control.
        /// </summary>
        /// <param name="postDataKey">The key identifier for the control.</param>
        /// <param name="postCollection">The collection of all incoming name values.</param>
        /// <returns>true if the server control's state changes as a result of the post back; otherwise false.</returns>
        protected virtual bool LoadPostData(string postDataKey, NameValueCollection postCollection)
        {
            EnsureChildControls();

            if (NeedHelper)
            {
                string szData = postCollection[HelperID];
                if (szData != null)
                {
                    return ProcessData(szData);
                }
            }

            return false;
        }

        /// <summary>
        /// Signals the server control object to notify the ASP.NET application that the state of the control has changed.
        /// </summary>
        protected virtual void RaisePostDataChangedEvent()
        {
        }

        /// <summary>
        /// Enables a server control to process an event raised when a form is posted to the server.
        /// </summary>
        /// <param name="eventArgument">A String that represents an optional event argument to be passed to the event handler.</param>
        protected virtual void RaisePostBackEvent(string eventArgument)
        {
        }

        /// <summary>
        /// Returns a true value to indicate that a hidden helper is needed by this control.
        /// </summary>
        protected virtual bool NeedHelper
        {
            get { return IsUpLevelBrowser; }
        }

        /// <summary>
        /// The ID of the hidden helper.
        /// </summary>
        protected virtual string HelperID
        {
            get
            {
                if (_szHelperID == null)
                {
                    _szHelperID = "__" + ClientID + "_State__";
                }

                return _szHelperID;
            }
        }

        /// <summary>
        /// Client-side script ID of the hidden helper.
        /// </summary>
        protected internal virtual string ClientHelperID
        {
            get
            {
                Control form = Util.FindForm(this);
                if (form != null)
                {
                    return "document." + form.ClientID + "." + HelperID;
                }

                return HelperID;
            }
        }

        /// <summary>
        /// The data to store inside the hidden helper.
        /// </summary>
        protected virtual string HelperData
        {
            get { return _szHelperData; }
            set { _szHelperData = value; }
        }

        /// <summary>
        /// Registers the control as needing post back handling if a hidden helper is needed.
        /// </summary>
        /// <param name="e">The event data.</param>
        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);

            // Ensure that LoadPostData is called
            if (NeedHelper && (Page != null))
            {
                Page.RegisterRequiresPostBack(this);
            }
        }

        /// <summary>
        /// Sets the hidden helper's data if a hidden helper is needed.
        /// </summary>
        /// <param name="e">The event data.</param>
        protected override void OnPreRender(EventArgs e)
        {
            base.OnPreRender(e);

            // Register the hidden input
            if (NeedHelper && (Page != null))
            {
                Page.RegisterHiddenField(HelperID, HelperData);
            }
        }

        // -------------------------------------------------------------------
        // Implementation of IPostBackDataHandler and IPostBackEventHandler
        // Override protected instance methods (at top) instead.
        // -------------------------------------------------------------------

        /// <summary>
        /// Processes post back data for a server control.
        /// </summary>
        /// <param name="postDataKey">The key identifier for the control.</param>
        /// <param name="postCollection">The collection of all incoming name values.</param>
        /// <returns>true if the server control's state changes as a result of the post back; otherwise false.</returns>
        bool IPostBackDataHandler.LoadPostData(string postDataKey, NameValueCollection postCollection)
        {
            return ((BasePostBackControl)this).LoadPostData(postDataKey, postCollection);
        }

        /// <summary>
        /// Signals the server control object to notify the ASP.NET application that the state of the control has changed.
        /// </summary>
        void IPostBackDataHandler.RaisePostDataChangedEvent()
        {
            ((BasePostBackControl)this).RaisePostDataChangedEvent();
        }

        /// <summary>
        /// Enables a server control to process an event raised when a form is posted to the server.
        /// </summary>
        /// <param name="eventArgument">A String that represents an optional event argument to be passed to the event handler.</param>
        void IPostBackEventHandler.RaisePostBackEvent(string eventArgument)
        {
            ((BasePostBackControl)this).RaisePostBackEvent(eventArgument);
        }
    }
}