How Can i write code for "Form1.cs" window is Deactive(close) when a form "Form2.cs" is loaded

(C#)- I have call'ed a Form "Form2.cs" from another form "Form1.cs", using form1's.show(); . When form2 is Actived [Shown] then automatically form1 should be close, but not form2. How can i write code for : when a form2 is activated, then form1 should be de-activate(nothing but close the window). Plz help soon...

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