wpf 4.5 - WPF Window Top property Won't Change -

i upgraded wpf app target framework 3.5 4.5 , code setting top property stopped working, won't change top value:

this.top=45; 

it stay previous value, never changed 45.
don't have type of animations.
why behaving this?

window xaml

<window x:class="salesorderlib.salesorderinquiry"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     xmlns:datepicker="clr-namespace:microsoft.windows.controls;assembly=wpftoolkit"     xmlns:ui="clr-namespace:salesorderlib.resources.ui"     xmlns:local="clr-namespace:salesorderlib"     xmlns:global="clr-namespace:salesorderlib.common"     xmlns:validation="clr-namespace:salesorderlib.validationrules"     background="{dynamicresource winbackgroundbrush}"      icon="resources/images/toolbar/orderinquiry.png"     title="sales order - inquiry mode"      height="630"      width="1024"     windowstate="normal"     showintaskbar="true"     resizemode="canresize"     windowstyle="singleborderwindow"     windowstartuplocation="manual"     focusmanager.focusedelement="{binding elementname=txtorderno}"     loaded="window_loaded"      contentrendered="window_contentrendered"     gotfocus="window_gotfocus"      closing="window_closing"     locationchanged="window_locationchanged"      activated="window_activated"> 

here try set top property in code behind:

 private void window_locationchanged(object sender, eventargs e)  {      try      {          if (this.top < 55d)              this.top = 55d;          if (this.height > 120d)              this.lstboxmediano.height = (this.height - 120d); //set mediano popup height.           thread.sleep(25); //allow window refresh.      }      catch (exception ex)      {          log.error(string.format(globalresources.msgexception, ex.tostring(), gettype().name, methodbase.getcurrentmethod().name));          messagebox.show(ex.message, globalresources.error, messageboxbutton.ok, messageboximage.error);      }  } 

are sure windowstartuplocation set manual? that's reason why shouldn't respect code.