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Is it possible to ignore/change the url from PostBackUrl in asp.Button from code behind?

I'm working with ASP.NET webforms and I'm wondering if it is possible to change/ignore the PostBackUrl so it won't change pages.
My button:
<asp:Button ID="continuebtn" OnClick="Continuebtn_Click" runat="server" PostBackUrl="~/client/profile.aspx" CssClass="btn btn-success btn-sm" Text="Continue"/>
And the OnClick function is:
protected void Continuebtn_Click(object sender, EventArgs e)
{
//some code
if(condition == false)
//change the url from PostBackUrl so it won't change pages
else
//keep the current Url
}
I've tried :
continuebtn.PostBackUrl = "";
continuebtn.Attributes["PostBackUrl"] = "return false";
continuebtn.Attributes.Remove("OnClick");
continuebtn.Attributes.Add("OnClick","return false");
continuebtn.OnClientClick = "return false;";
add return; to if
I tried to remove the PostBackUrl from the button and add it from the code behind with continuebtn.PostBackUrl = "~/client/profile.aspx" but it didn't work either.

There are two big reasons to use post-back URL in place of say using a code behind click event and say then response.Redirect("some web page").
First up, post-back url passes the previous page!!!!!
So, if you have say a text box and a button like this: (or evne a grid view)
Now you can use code behind to jump to the next page, or you can use/set/have post-back url set.
If you use post-back URL. Then you don't need to write a code behind stub, and you ALSO get use of previous page in the next page on-load event (you ONLY can pick up previous page in load - first time).
eg:
protected void Page_Load(object sender, System.EventArgs e)
{
if (IsPostBack == false)
{
TextBox tbox;
tbox = Page.PreviousPage.FindControl("TextBox1");
Debug.Print("Text box = " + tbox.Text);
TextBox1.Text = s;
}
}
}
so post-back url = a great way to pass/get at/use the previous page values with find control. Now if you not needing to do this, then you probably should not use post-back URL, since you are bulking up the payload for the next page (it will contain the current page, and you have as noted use of "previous page". However, it is a fantastic way to avoid parameters and/or cluttering up session() just to pass a bunch of values. Just use post-back URL and then like "magic" then previous page can be used. if you don't use post-back URL then previous page is null and not valid.
And if you place two buttons on the page? Can you set postback url? Sure you can set that control, text box or do anything you like - but do keep in mind that the code behind is running AFTER a post-back, and it will of course be too late to change a button that CAUSED the post back.
So, you can certainly do this in button2 click even to change button1:
protected void Button3_Click(object sender, EventArgs e)
{
Button1.PostBackUrl = "";
}
So in above, button3 click event and code behind wiped out the post-back URL of button one. Or we can of course set the url to anything we want.
Now, the code behind is done, page is rendered and THEN sent back down to the browser with the above change. If user hits button1, then no postback url exists - we blew it out with the above code.
However, in the SAME button event? no, it is too late to change or modify the post-back.
In that case, and if you need "conditional" jump? Then you need to delete and remove the post-back url, and simply put the logic you need to determine the ya, or nay jump based on the code behind for that click event.
HOWEVER - and a BIG WHOPPER however? If you JUST use a response.Redirect("some web page") in that code behind, then you DROPPIGN THE MAIN reason as to why the developer used post-back URL in the first place. That main, big, huge, large reason is that post-back URL gives the next page in line FULL USE of the previous page values with "previous page". If you do NOT use post-back URL, then you can't use previous page to pass all those values and inspect and get and grab control values from the previous page.
So what if you really did need the "abilities" that post-back URL provides (that ability of course is "previous" page in the next page load!
In that case, then you have to use Server.Transfer() in that code stub to get use of previous page in the next page that loads.
So, regardless:
You can't change post-back URL in the same button code event - it is too late.
If you are going to then put the logic in the code event? Then be VERY VERY aware that if you use a response.Redirect("some web page"), then you may VERY well be breaking the functionally of why in the first place the developer used post-back url (to have use of "previous page".
Your suggested idea to modify client side the post-back url in one button click, and then do a js "click" of that button you just changed the post-back url should also work (good idea!!!).
But, I would thing that just using a code behind stub in the click event, and then the code can choose to navagate or jump to the next page based on that code? Right?
However, if you do that, then you will break the "features" of post-back URL in pasing page prevous.
In that case? Then you need to use a server.Transfer("to next web page") in place of response.Redirect("to next web page), since a server.Transfer will give you use of "page previous" in the next page load event JUST LIKE post-back URL does!
Of course with a server.Transfer, you will note that the web page URL does not change or update - and this is a fall out of having to do this. (and may, or may not matter to you).

Clear Fields Button (redirect not working)?

I have a webform with a "clear all fields" button, but it's not working properly. When I click the button on the rendered page, it directs me to another page on the local server, but not the one I have listed here.
protected void btn_Clear_Click(object sender, EventArgs e)
{
Response.Redirect("~/ContentRequest/PR_Event.aspx", true);
}
I'm not sure what I can do...

You can simply use Request.RawUrl to redirect back to current page.
Response.Redirect(Request.RawUrl, true)
However, if you want to just clear fields, you might want to use jQuery or javascript at client-side to avoid a round trip to server.

viewstate disappears on response.redirect

On my asp.net c# page I have two text boxes(start and end dates) with ajax CalendarExtenders. The user selects a start date and then an end date. On selecting the end date, I bind my grid as shown below;
protected void calEndDate_TextChanged(object sender, EventArgs e)
{
BindGrid();
}
In the grid I have a command button with the following code
protected void gvAllRoomStatus_RowCommand(object sender, GridViewCommandEventArgs e)
{
if (e.CommandName == "Manage")
{
GridViewRow row = gvAllRoomStatus.Rows[Convert.ToInt16(e.CommandArgument)];
int BookingID = Convert.ToInt32(row.Cells[1].Text);
DataClassesDataContext context = new DataClassesDataContext();
Session["BookingID"] = BookingID;
Response.Redirect("CheckIn.aspx");
}
}
When the user goes to that page and clicks the back button all the selected dates and the gridview data disappears. Any ideas why the viewstate is disappearing?

ViewState belongs to the current Page.
Have a look: http://www.codeproject.com/Articles/37753/Access-ViewState-Across-Pages
Yes, we can access the viewstate variables across pages. This is only
possible if Cross Page Posting or Server.transfer is used to redirect
the user to other page. If Response.redirect is used, then ViewState
cannot be accessed across pages.
So you could use Server.Transfer instead or use the Session.

Viewstate to look at it in a very simplified way is to see it as a carbon copy or cache of the last state of the page you are currently on. Therefore doing a redirect to any page, even the same page itself, is essentially a fresh start. The viewstate no longer applies as for all intent and purpose, you are on a new page.
As Tim suggests in his post, either store the required data as a session variable or use a server.transfer.
Take a look here for a nice overview of viewstate:
http://www.codeproject.com/Articles/37753/Access-ViewState-Across-Pages

In my opinion the issue you have is because you make auto post backs with calEndDate_TextChanged using Ajax.
After your submit, when you press the back button the browser can not remember neither can save what you have change with all that auto post data with Ajax calls, and you lose them.
For me remove the Text Change auto post back, remove the Ajax because you do not needed and make a regular full post back when the user submit their data.
Then when you make back with the browser, browser load the previous state and most of the browsers remember what and all the input of the user. Also on that back the viewstate is the same as previous because did not have change from the Ajax.

Activating a ASP Multiview control's view from other page without querystring/session

I was looking for an alternative that may be used to activate a multiview control of other page without passing a querystring/session variable.
Basically, my Home.aspx page has a link that takes us to a specific page say "NewPage.aspx". The NewPage.aspx page has a multiview control that has three child views.
I want to click on the link of the Home.aspx and go to NewPage.aspx with MultiView1.ActiveViewIndex=1. Please remember that I do not want to pass any querystring variable as that link already contains some encrypted data as querystring and adding another variable can cause the data to corrupt. Maintaining a session isn't a solution as well because the application is quite big.
Any inbuilt method that can activate that view? (I don't seem to be talking practical but any help is really appreciated)

If you are asking about how navigate to this page I would wire up a button event (I prefer to do so in OnInit). Something like this:
protected override void OnInit(EventArgs e)
{
base.OnInit(e);
this.btnlinkclick.Click += new EventHandler(btnlinkclick_Click);
}
void btnlinkclick_Click(object sender, EventArgs e)
{
this.MultiView1.ActiveViewIndex = 1;
}
This should work for you.

Don't Change URL in Browser When Clicking <asp:LinkButton>

I have an ASP.NET page that uses a menu based on asp:LinkButton control in a Master page. When a user selects a menu item, an onclick handler calls a method in my C# code. The method it calls just does a Server.Transfer() to a new page. From what I have read, this is not supposed to change the URL displayed in the browser.
The problem is it that the URL changes in the browser as the user navigates the menu to different pages.
Here is an item in the menu:
<asp:LinkButton id="foo" runat="server" onclick="changeToHelp"><span>Help</span>
</asp:LinkButton>
In my C# code, I handle the event with a method like:
protected void changeToHelp(object sender, EventArgs e)
{
Server.Transfer("Help.aspx");
}
Any ideas how I can navigate through the menu without the browser's URL bar changing?

You can use iframes to make sure that URL of browser doesn't change.
In Page_Load you can change src attribute of iframe to help.aspx

Try Server.Execute("Help.aspx") instead. You can preserve the form if you need by using
Server.Execute("Help.aspx",true);