First, you can choose one from the available borders:
https://msdn.microsoft.com/en-us/library/system.windows.forms.form.formborderstyle%28v=vs.110%29.aspx[
^].
If this is not enough, you can use borderless form and draw a border in the client area using overridden
OnPaint
method. To avoid intersection with the form's content, add some
Padding
. But if you want to do it in more accurate and universal way (say, if you develop a universal base class for other form classes), you can use adjust the client size by overriding
Control.SetClientSizeCore
, to make some extra room for your border:
https://msdn.microsoft.com/en-us/library/system.windows.forms.control.setclientsizecore%28v=vs.110%29.aspx[
^].
—SA