Can some one please tell me how to I practical of page life cycle of .NET

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C#

ASP.NET

Can some one please tell me how to i practical of Page Life cycle of .net how to write event of page and where write like how to Dynamically define master page and themes and how to or where define value of view state and also in which event of life cycle please explain me it i am beginner of asp.net C#. thank you in advance 

What I have tried:

void page_preinit(object sender, eventargs e)
{
this.masterpagefile = "~/site.master/";
}

i wrote this code in master.cs page it it write or wrong and how to chech its work and like that i want to pratice all event with real value please help me