Hotkeys only work when your app has the focus - otherwise we couldn't use them at all - think how many key combinations Excel uses and how many of them are also used (for a different purpose) by Word. If hotkeys were spread across all apps, then which one gets F2 when I press it?
What you are trying to do needs something a lot more complicated: Global Hooks - and there are problems here.
1) Global hooking in C# is possible, but very complicated and prone to error. When errors happen, your whole system can easily become unstable. And that includes while you are trying to develop the code! Backup well, backup often.
2) Using F5 and F7 as "global keys" will mess you up, not just users. F5 is Visual Studio for "run" so if your app grabs it, you can't develop software at all easily any more.
3) Global hooking is one way to allow keyloggers to work, so do not expect it to work in future versions of Windows - security concerns may mean it gets disabled or requires elevation.
4) You start grabbing keys off users to make your app work and some - if not most - are going to get very, very annoyed. Many of my apps use most of the function keys (with and without SHIFT, CTRL, AN DALT combinations) as "Power user shortcuts" and if you start grabbing them your software is goign to get uninstalled with extreme prejudice ...
If after that you decide to go ahead, then start here:
Global Hooks C#[
^] - but don't say you weren't warned!
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