I have forms with tab pages and they are resizing so the problem is definitely not there. But since we don't wee how you set your stuff, we can't fully help you.
One blind guess: have you set the Anchor property for your controls inside the tabpages?
RIAS
ASKER
Yes,
Tried Anchor but they resize and they stick to each other.May be I am doing something terrible wrong
You can use the screen class to determine the resolution of the screen:
https://msdn.microsoft.com/en-us/library/system.windows.forms.screen.aspx
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You can then set the form's height and width to whatever you like.