Web Part Life Cycle starts with
OnInit – Configuration values set using WebBrowsable properties and those in web part task pane are loaded into the web part.
LoadViewState – The view state of the web part is populated over here.
CreateChildControls – All the controls specified are created and added to controls collection. When the page is being rendered for the first time the method generally occurs after the OnLoad() event. In case of postback, it is called before the OnLoad() event. We can make use of EnsureChildControls() - It checks to see if the CreateChildControls method has yet been called, and if it has not, calls it.
User Generated Event – for e.g. button click on the web part.
OnPreRender – Here we can change any of the web part properties before the control output is
RenderContents – Html Output is generated.
SaveViewState - View state of the web part is serialized and saved.