c# - Replacing specific numbers with String.Replace or Regex.Replace -

just having little problem in attempting string or regex replace on specific numbers in string.

for example, in string

@1 having lunch @10 @11 

i replace "@1", "@10" , "@11" respective values indicated below.

"@1" replace "@bob" "@10" replace "@joe" "@11" replace "@sam" 

so final output like

"@bob having lunch @joe @sam" 

attempts

string.replace("@1", "@bob") 

results in following

@bob having lunch @bob0 @bob1 

any thoughts on solution might be?

assuming placeholder start @ , contain digits, can use regex.replace overload accepts matchevaluator delegate pick replacement value dictionary:

var regex = new regex(@"@\d+");  var dict = new dictionary<string, string> {     {"@1","@bob"},     {"@10","@joe"},     {"@11","@sam"}, };  var input = "@1 having lunch @10 @11"; var result=regex.replace(input, m => dict[m.value]); 

the result "@bob having lunch @joe @sam"

there few advantages compared multiple string.replace calls:

1. the code more concise, arbitrary number of placeholders
2. you avoid mistakes due order of replacements (eg @11 must come before @1)
3. it's faster because don't need search , replace placeholders multiple times
4. it doesn't create temporary strings each parameter. can issue server applications because large number of orphaned strings put pressure on garbage collector

the reason advantages 3-4 regex parse input , create internal representation contains indexes match. when time comes create final string, uses stringbuilder read characters original string substitute replacement values when match encountered.