Since Visual Studio 2012 changed its regex syntax, the original answers by Ala translate into the following in VS 2012:
Remove single blank lines
Old:
^:b*$
New:
^(?([^
])s)*
?$
?
Visual Studio 2013 (thanks to BozoJoe and Joe Johnston):
^s*$
Remove double blank lines
Old:
^:b*
:b*
New:
^(?([^
])s)*
?
(?([^
])s)*
?
Rolls right off your tongue.
Here is the conversion sheet from MSDN.
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