.net - Regular expression for no white space at start or end, but allow white space in middle, but also allow only one char inputs:

Question

Regular expression for no white space at start or end, but allow white space in middle, but also allow only one char inputs:

The closest I have got is : ^([^s])([sa-zA-Z0-9_-]*)([^s])$

The problem with this is that it will only pass if the input is three or more chars, I need it to accept a single char and pass. EG:

The following should pass (using " for easy of reading, not required in string)

"A"
"A B"
"Hello There"

The following should fail

" A"
"A "
" A "
" test"

also needs to only allow A-Z a-z 0-9 - _ though out, with addition of spaces in middle section but not at start or end

Any ideas?

Thanks

Answer 1

Non-spaces, optionally followed by multiple groups of spaces then non-spaces:

^[^s]+(s+[^s]+)*$

Edit:

To include the character restrictions, just replace non-space classes with allowable characters:

^[-_a-zA-Z0-9]+(s+[-_a-zA-Z0-9]+)*$

Also, consider being Unicode friendly and using something like

^[-_p{Alnum}]+(s+[-_p{Alnum}]+)*$

(assuming your regex interpreter allows it).