Create a Preloader/Loading screen in Blend/Wpf

Just Follow the steps to create an animated Preloader :-
1) First take an "Eclipse" from Assets or toolbox .
      -->Goto properties of "Eclipse" , 
              change its fill color to transparent/no brush .
                             (make Alpha value 0 to make it transparent in blend)
     -->And give its stroke color & size to "5" as per your requirement.
2) Second take a "Rectangle" from Assets.
     -->In properties make its stroke color to "NoBrush".
     -->then make a copy of that rentangle by right click it & select copy ,
          then paste it (or by "Ctrl+C" & paste "ctrl+V").
     -->Now we have to two rectangle ,rotate one rectangle
          to virtical 90 degree (In properties ->select Transform->select Rotate). 
     -->Now First select Two rectangles then eclipse ,Then right click on
          these selected items ,select "Combine"->select "Substract".
     -->Now we have cuted circle,Then unselect all ,now select
         inner bars in circle & delete these bars. now circle/eclipse
         converted to path.
3)  Make copy of  circle,
      --> make it smaller & change its stroke size to "2" .
      --> Place it Inside the big circle.
4) Now make a new Animation on storyboard.
      -->Set a keyframe at "0" second for both big & small circle.
      -->Take timeline bar to 1/2 second then select both circles/paths
                   & in proprties->Transform->rotate->change angle to 50 to 60.
      -->Unselect all ,then take timeline bar to 1 sec,select bigcircle
            change its angle to 80 to 90, then select small circle change its
                angle to  0 to -10.
      similarly do change as you like. & set the last/final time bar to 0 angle
      for both circles.
5) For infinite looping go to "object & timeline" bar select paths or big &
    small circles ->Render transform->rotation->Angle. Then right click
    on both "angle"s  time line ,select "edit repeat count"->set it
                                      to "Forever" then ok.

Now your preloader is ready....Enjoy.......

OR Watch This Video