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You can add your own syntax definitions using TextMate bundles: See Manual

A quick search didn't bring up results for "TextMate ASP.net MVC bundle" though, so I guess there isn't a TextMate-compatible syntax definition for this markup language yet. The only way would be to create your own syntax definition based on maybe the standard HTML bundle.
Das sind die normalen Mac-Tastenkombinationen. Unter Mac OS X gibt es dafür die sogenannte Tastaturübersicht, wo man sich das alles ansehen kann. Eine Seite kenne ich leider nicht, ich bin aber sicher, dass es irgendwo eine gibt :)
[ = Alt+5

] = Alt+6

{ = Alt+8

} = Alt+9


Auf dieser Seite stehen wertvolle Tipps von Logitech: http://www.logitech.com/de-de/67/8694

If you have German settings, try Alt-Shift-7 for backslash and Alt-L for the @ character. 

Make sure you have chosen the correct virtual keyboard using the globe symbol before using the hardware keyboard. The mapping of the hardware keys depends on the virtual keyboard layout.
There is a search bar on the top of the symbol list that allows you to filter the list.
There is already a mechanism that won't open a file again if the app crashes while opening at startup. So this shouldn't happen more than once.
This should work. Can you please send me a screenshot of your #Textastic folder and one theme file so I can try to reproduce the issue? Send it to support@textasticapp.com.