Looking at the documentation , you need to have braces around only F1. Try this to see if it works.
System.Windows.Forms.SendKeys.Send("^+{F1}");
From the above link, inserting the ^ and + characters in curly braces, you send an alphabetic character.
The plus sign (+), carriage (^), percent sign (%), tilde (~) and parentheses () have special meanings for SendKeys. To indicate one of these characters, enclose it in curly braces ({})
added by barlop - explanatory note -
(from the above documentation)
SHIFT + CTRL ^ ALT %
and
F1 {F1} F2 {F2}
Mark hall
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