c# - How to find the index of .First match? -

i'm using this:

foreach (var item in set) {     string matchingstring = conlines.firstordefault(r => (r.indexof(item.firstparam) >= 0 && r.indexof(item.secondparam) >= 0) && (r.indexof(item.firstparam) < r.indexof(item.secondparam))); } 

where:

list<string> conlines = ... 

and

public class classname {     public string firstparam { get; set; }     public string secondparam { get; set; } }      public static list<classname> set = .... 

and want know @ index of conlines matchingstring found.

at end of day, i'm trying search through conlines, string string, matches firstparam , secondparam (sequentially, in same string of conlines). if match found, want change string in conlines. whether line finds match , gets changed or not, want print out. i'm reading in conlines , printing out including changes in lines found match firstparam , secondparam.

example:

if conlines were:

alpha beta dog cat chair ramp table seat blog journal article letter 

and firstparam, secondparam included:

ramp, table article, letter 

and changes made add -01 matches, printing out:

alpha beta dog cat char ramp-01 table-01 seat blog journal article-01 letter-01 

no matter how find index, it's going sub-optimal. you'll wind enumerating collection twice. instead, should either:

1. use for loop loop on collection (if possible). way, whenever find fist match, you'll have index (only works if collection exposes , indexer , pre-calculated length/count property):

   for(var = 0; < collection.count; i++) {     if(collection[i] == query)     {         // have match collection[i] , index in     } } 

2. loop on collection using getenumerator , count index using counter. work ienumerable:

   var enumerator = collection.getenumerator(); var count = 0;  while(enumerator.movenext()) {     if(enumerator.current == query)     {         // have match in enumerator.current , index in count     }     count++; } 

either way, you'll have loop on collection single time rather twice (once firstordefault , again index.