Develop Reference

To stop reloading web page In Asp.net on any button click

how stop postback on any button click. My page is reloading as soon as i click on reset button on the registration page, i want to reset the form without reloading the page itself.

You have two possibilities:
Simply set the attribute AutoPostBack="false" on your button or whatever control.
As an alternative you could also add the following javascript to the click event of the button :
onclick="return false"
This prevents the button from submitting.

Try following:
<asp:button runat="server".... OnClientClick="return false;" />

First you have to know about Sever Control and normal HTML control.
If you used Server Button Control then your Page reload on each click.
If you wan to stop it then you have to use AutoPostBack="false", using this your server side method calling is stop.
Otherwise use Normal HTML Button Control and use JavaScript to reset your form.

Message box cant be displayed When run in IIS?

I wants to display an OK/CANCEL message box. I have written like this.
if (MessageBox.Show("Are you sure you wants to Save the details ? ", "Validate", MessageBoxButtons.OKCancel) == DialogResult.OK)
{
// do something if "OK "
}
it works locally well.. but on IIS shows an error " Showing a modal dialog box or form when the application is not running in UserInteractive mode is not a valid operation. Specify the ServiceNotification or DefaultDesktopOnly style to display a notification from a service application."
please help.

To get the effect I believe you are wanting, you'll want to use the Javascript confirm() function. It is typically used like this:
<asp:Button runat="server" OnClientClick="return confirm('Are you sure you want to save the details?')" id="btnSubmit" OnClick="btnSubmit_Click" />
This would, upon clicking the button, display a confirmation box that would stop the server OnClick event from firing if the user clicks No, Cancel, etc.
OnClientClick will render as an onclick event on the <input> tag. The rest is determined by the browser's handling of Javascript. See What's the effect of adding 'return false' to a click event listener? for more details on what the return value of the code in OnClick (OnClientClick) does.
Here's an example of the return values of confirm() using Chrome. For the first execution I had clicked Cancel.

Is it possible for a server to treat a postback as not a postback?

Currently I have a site that loads everything on initial load (when it's not a postback). Then it proceeds to load more data that should be fine to load regardless if it's postback or not. I thought everytime the page is refreshed or the button is pressed there is a postback. What I thought that if the user doesn't go to another page, any action he takes will be a postback.
However I'm getting very inconsistent errors when the site is actually on a server and was curious if perhaps, when clicking a button after a bit of inactivity, will the server possibly forget about the previous activity and treat the action as the person hitting the site for the first time again?
Below is how the button is defined....
<asp:Button CssClass="btn btn-default controls" ID="btnAddAdditionalCom" runat="server" Text="Add Comment" OnClick="btnAddAdditionalCom_Click"/>

Any asp:button click will cause a postback to the server because asp is a server side language so it has to talk to the server to execute the button click. If you want to do button clicks without talking to the server use something like javascript

You cant modify it.
Because this is a essential concepts in asp.net.
Even you cant change the value of IsPostback Property (It has no setter).
If you want to treat Postback as page load then u forgot the need of IsPostback

JavaScript Yes/No Preceding ASP.NET Button Event

Hi I'm trying to learn more JavaScript AJAX. Basically I would like to have a popup Yes No on a delete button that would precede the actual C# event being fired. I could do this all in C# but I know doing it client side would be beneficial as it would reduce server load.
I'm not sure exactly how to go about this. Any ideas?

You can use the javascript function called confirm
onclick="return confirm ('Are you sure you want to delete this _____?');"
This text parameter is the text that will be shown in the modal with the yes and no.
The Yes returns true which allows the postback to continue, but the No returns false and will stop the postback.
EDIT:
As mentioned by XaiSoft and Cybernate, if you are using an ASP.NET button you can also use the OnClientClick property which will be translated to onclick by the server.

You can use OnClientClick property of the asp:Button.. along with the JS confirm..
Try something like the code below in your aspx/ascx/master:
<asp:Button id="cmdSubmit" OnClientClick="return confirm('Are you sure?')" runat="server" .../>

You can also use jQuery instead of the ugly default confirm. Here is a question addressing that.

ModalPopup inside the UpdatePanel with default form values

I have a ModalPopupExtender inside an UpdatePanel which opens an input form. The problem is when I click the "Edit" button (which is also inside the UpdatePanel) I want to fill the form with existing values using server side code. But it OnClick method of the button doesn't seem to work.
My question is: How can I make the serverside code run first, than show the edit form?

You need to show the ModalPopupExtender from server side.
First, link the ModalPopupExtender's TargetControlID to a dummy hiddenfield or a button with style="display:none" instead of the "Edit" button. I know it's sound stupid, but it's a know workaround.
Then make sure the asp.net the "Edit" button is set as a asyncpostbacktrigger if children as trigger is set to false.
Also set CausesValidation="false" to avoid the postback to be blocked by unrelated validators on the page.
Finally, At the end of "Edit" button's click event, call ModalPopupExtender.Show() to display the pop up.