.net - Regex to find first extension in OpenFileDialog filter string -

i want find first extension in list of exentions in openfiledialog file filter string.

consider below example -

image files(*.bmp;*.jpg;*.gif)|*.bmp;*.jpg;*.gif

text files (*.txt)|*.txt

for first case - if user tries save file without extension default want append .bmp extension filename.

for second case - if user tries save file without extension default want append .txt extension filename.

rather use regex split string, use split function suggested sysdragon - there no earthly reason why wouldn't this. once have second part of original string regex bmp *.bmp;*.jpg;*.gif 1 , match.

^\|\*\.(\w{1,4}); 

simply put, says following:

• ^ start @ beginning of string
• \| find pipe character (the \ delimits because equivalent of or in regex)
• \* find single * character (again, delimited because * means 'zero or more repetitions' in regex)
• \. find single period (delimited because means 'any character' normally)
• (\w{1,4}) find @ least 1 , 4 alphanumeric characters. capturing group can obtain match object.
• ; find semi colon

i have arbitrarily chosen 1-4 alphanumeric characters can adjust suit needs, instance {3} mean 'find three', [a-za-z]{1,3} mean 'find @ least 1 , 3 matches letters a-z , a-z'.

since wanted first extension want amend pattern give extensions match collection. in fact regex simpler (but why return n matches when 1 do?) , i'll levae learning exercise :-)