I solved the problem

In the app.xaml.cs, I did

private void Application_Startup(object sender, StartupEventArgs e)
        {       
            string url = App.Current.Host.NavigationState.ToString();
            if (url != "")
            {
                string[] pagename = url.Split('/');
                string page = string.Empty;
                foreach (string str in pagename)
                {
                    int indexval = str.IndexOf('?');
                    if (indexval != -1)
                        page = str.Substring(0, indexval);
                }
                if (page == "MainPage.xaml")
                    this.RootVisual = new MainPage();
            }
            else
            {
                this.RootVisual = new Page1();
            }
        }

and on hyperlinkbutton click event of MainPage.xaml.cs

   btn.TargetName="_blank";
            string url = @"http://localhost:8185/modules/tcm/Web.CortexTestPage.aspx#/MainPage.xaml?TestCaseId=" + btn.Content.ToString();
            btn.NavigateUri = new Uri(url, UriKind.RelativeOrAbsolute);

Now I can be able to open multiple window in new browser.

Any other alternative or suggestion are welcome.

Thanks for everyone support...

-Pankaj

Thanks for your reply

but this is not what I want.

I don't want to navigate I want to open seprately a new window on click of hyperlinkbutton.

I used the following

<HyperlinkButton Click="Navigate_Click" Content="NewPage" NavigateUri="http://localhost:1254/NavigateTestPage.aspx#/View/Page1.xaml?TestCaseid=12" TargetName="_blank" Tag="/View/Page1.xaml"></HyperlinkButton>           

It opens the new browser window with the contents of my mainpage as well as Page1.But here I get stucked.I want to show the content of Page1 only in new browser.

Can you help me out.

- Pankaj

Thanks for your reply...Yes I am using xamwebgrid.I want to open an xaml page when I click on hyperlinkbutton.not in the parent browser but out of browser(means in new browser).on each hyperlink button click I want tje new window get open.Hope you got my point...

-Pankaj