Code snippet of the day: persist the scroll position of an ASP. NET page

Sometimes we need to persist the scroll position of a page after a post back and not reset to the top, in ASP. NET 2.0, you can use the smartnavigation feature. however, setting smartnavigation to true in the page directive of an ASP. NET page is known to cause some problems with the rendering of the page. microsoft has confirmed that defaultredirect does not work and has posted a KB article for it.

As an alternative, here is JavaScript code to create a hidden field on the page and taps into the onscroll and onload events of the page's body. the code shown here is in the page's load event handler in the code behind file.

/**/ /// <Summary>
///Persist scrollbar's position after a PostBack
/// </Summary>
Private   Void Persistscrollposition ()
{
Stringbuilder savescrollposition =   New Stringbuilder ();
Stringbuilder setscrollposition =   New Stringbuilder ();

Registerhiddenfield ( " _ Scrollpos " , " 0 " );

Savescrollposition. append ( " <Script language = 'javascript '> " );
Savescrollposition. append ( " Function savescrollposition (){ " );
Savescrollposition. append ( " Document. Forms [0]. _ scrollpos. value = Document. Body. scrolltop; " );
Savescrollposition. append ( " } " );
Savescrollposition. append ( " Document. Body. onscroll = savescrollposition; " );
Savescrollposition. append ( " </SCRIPT> " );

Registerstartupscript ( " Savescroll " , Savescrollposition. tostring ());

If (Page. ispostback)
{
Setscrollposition. append ( " <Script language = 'javascript '> " );
Setscrollposition. append ( " Function setscrollposition (){ " );
Setscrollposition. append ( " Document. Body. scrolltop = "   + Request [ " _ Scrollpos " ] +   " ; " );
Setscrollposition. append ( " } " );
Setscrollposition. append ( " Document. Body. onload = setscrollposition; " );
Setscrollposition. append ( " </SCRIPT> " );

Registerstartupscript ( " Setscroll " , Setscrollposition. tostring ());
}
}

Hope this helps