title: how to unlock or log in windows by app itself
body: <p>As we all know,we can use such api as "LockWorkStation()" in "user32.dll" to lock windows.
  But how to unlock it? <br/></p>
  
  <p>For example, if i run an app at first, I want the app to unlock windows by itself after 30 second.
  How to do it? In another word, if auto-logging in, windows will read the username and password from regedit and then use an api to login by those. 
  Now i need the api. It must exist, but it seems not to make public.<br/></p>
  
  <p>I can get the app the username and password of the windows.<br/></p>
  
  <p>It seems that there is some Api in WBF.But you know,the resource is too less.
  I don't want to send keyboard message to solve the problem,for it is the worst method.<br/></p>