Why did i must click second times to create and display session value rather than 1 time???

Hello everybody!
My problem is i have two usercontrols inside .aspx page or masterpage .One of two usercontrols is create session and the another display that session value. But when i click on button to create session and Meantime i display session value in the another on page_load event but it not work untill i click on that button second time.? Someone help me and explain for me know how is it! Thanks. And this is Markup of .aspx page and two usercontrols.
.Aspx file
<body> <form id="form1" runat="server"> <div> <uc3:create_session ID="create_session1" runat="server" /> </div> <div> <uc2:displaysession ID="displaysession1" runat="server" /> </div> </form> </body> And Create_session usercontrol
<%@ Co ...