Check this out

[Magiaus]

Friends, Romans, Frogs lend me your ears.

Do you need to load Data based on one page based on an action from another page? Do you need to do some weird JavaScript and then post back? Do you want to use the JavaScript setTimeOut to create a really funky Server Side Timer?

I say unto you no longer shall you fight to be able to raise a custom PostBack Event from your JavaScript. Behold the very short, very ugly, very over rated PostBackEvent.

Simply drop one on your WebForm write your event code and invoke it from JavaScript you write and only JavaScript you write.

Not only that but it is only slightly agrivating at Design Time..........

using System;
using System.ComponentModel;

using System.Web;
using System.Web.UI;
using System.Web.UI.Design;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;

namespace Controls
{
    /// <summary>Provides a quick drop on controless PostBackEvent.</summary>
    /// <developer>Zeke Naulty</developer>
    /// <createdOn>3/17/05</createdOn>
    [Designer(typeof(PostBackEvent.PostBackDesigner), typeof(ControlDesigner))]
    public class PostBackEvent : Control, IPostBackEventHandler
    {
        internal class PostBackDesigner : ControlDesigner
        {
            public override string GetDesignTimeHtml()
            {
                PostBackEvent c = null;
                if(Component is PostBackEvent) c = (PostBackEvent)Component;
                if(c != null) return "<!-- PostBackEvent " + c.ID + "(" + c.UniqueID + ")  Purpose: " + c.EventPurpose + " -->";
                return null;
            }
        }
        public event EventHandler PostBack;
        private string _eventName = "CustomPostBack";
        public string EventPurpose
        {
            get{return _eventName;}
            set{if(_eventName != value) _eventName = value;}
        }
        public PostBackEvent(){}
        protected virtual void OnPostBack(EventArgs e){if(PostBack != null) PostBack(this, e);}
        public void RaisePostBackEvent(string eventArgument)
        {
            EventArgs e = new EventArgs();
            OnPostBack(e);
        }
        protected override void Render(System.Web.UI.HtmlTextWriter writer)
        {
            writer.Write("<!-- PostBackEvent " + this.ID + "(" + this.UniqueID + ")  Purpose: " + _eventName + " -->");
        }
        protected override void OnPreRender(System.EventArgs e)
        {
            this.Page.GetPostBackClientEvent(this, "");
            base.OnPreRender(e);
        }
    }
} 

[Coool]

Really Bump for me..
Can anyone explain how to implement this.. ?

[Magiaus]

Drop the control on a page(we say it has an id of "PBEvent"). Implement an event handler for it's event(

protected void PBEvent_PostBackEvent(object sender, EventArgs e){/*your code*/}

). Then when ever you need to raise an event from JavaScript

<script>__doPostBack('PBEvent','');</script>

[Magiaus]

I HATE VB

    Public Class PostBackEvent
        Inherits Control
        Implements System.Web.UI.IPostBackEventHandler

        Public Sub RaisePostBackEvent(ByVal eventArgument As String) Implements System.Web.UI.IPostBackEventHandler.RaisePostBackEvent

        End Sub

        Protected Overrides Sub OnPreRender(ByVal e As System.EventArgs)
            Dim s As String = Me.Page.GetPostBackEventReference(Me) 'force the page to have __doPostBack

            MyBase.OnPreRender(e)
        End Sub

        Protected Overrides Sub Render(ByVal writer As System.Web.UI.HtmlTextWriter)
            writer.WriteLine("<!-- Custom PostBack JavaScript Provider:" & Me.ID & " -->")
        End Sub
    End Class

You'll notice the vb one is not completed, because VB is EVIL!!!!

[mendhak]

Nice. Could you rename the thread title to something search friendly, like "Custom Postback Class" ? ZEKE.

[Magiaus]

Good, idea.

[Coool]

Sorry for late posting. I checked the above code and i noticed that it works fine. But instead of creating a whole new control i have put this in Page Init.

Me.Page.ClientScript.GetPostBackEventReference(Me, "")

I had one question in my mind .. When I put the above code in my Page i actually made it commented. so that I can check whether __doPostBack class really created without it or not? I have no control in my form. After running the appication i confirmed - __doPostBack event was not created. Now I removed the comment and run the project and i can Now see the __doPostBack event generated. until this it run as per my expectation.

Now but when i made the Code commented again, page still generate __doPostBack.

My Basic understanding is - at least one control needs to be set to Visible, for the server to generate the __doPostBack function in our page.

Can anyone tell this strange behavior ?

[Magiaus]

One control must call Me.Page.GetPostBackEventReference(ctl,"arg"), and MS states the place to call this is in prerender; invisible controls don't render or prerender

Page.GetPostBackEventReference(control, argument)

invokes internal/friend Page.RegisterPostBackScript() and returns you the needed jscript call.

Think about in terms of page weight, unless a rendered control is going to call that js func. It is a waste to render it. That is the point of the render chain.

[Coool]

Thanks for Information but I wanted to know the strange behaviour i mentioned above. Anyway No Pro. Whatever it is i can now manage to force the page to have __doPostBack method with RIGHT METHOD. All bec'z of u.

Thanks a lot once again..

[Magiaus]

that's the point of the post