Replacing value in XML tags in C# using Regex -

i trying replace value between 2 xml tags default numeric value.

in following string, need replace value of dob w/ 1900-01-01.

input:

<firstname>test</firstname> <dob>test</dob> <tt:lastname>test</tt:lastname> <tt:dob>test</tt:dob> 

desired output:

<firstname>test</firstname> <dob>1900-01-01</dob> <tt:lastname>test</tt:lastname> <tt:dob>1900-01-01</tt:dob> 

this have:

string pattern = @"<((dob|tt:dob).*>).*?</\1"; string input = "<firstname>test</firstname><dob>test</dob><tt:lastname>test</tt:lastname><tt:dob>test</tt:dob>"; string replacement = "<$1 1900-01-01 </$1"; regex rgx = new regex(pattern); string result = rgx.replace(input, replacement); 

which gives me:

<dob> 1900-01-01 </dob> <tt:dob> 1900-01-01 </tt:dob> 

i'm able set default date, not without putting space between value , 1st subpattern in replacement variable. if take out spaces, reads "1900" part of first subpattern.

here link regex test: https://regex101.com/r/fk3ya5/6

is there way replace values number without using space or quotes?

jon skeet correct, should use xelement api. however, answer question, can follows changing replacement regex this:

string replacement = "<${1}1900-01-01 </$1"; 

notice how $1 became ${1}. see here more details