Is String Contains faster than String IndexOf

Question

I have a string buffer of about 2000 characters and need to check the buffer if it contains a specific string  Will do the check in a ASP NET 2 0 webapp for every webrequest   Does anyone know if the String Contains method performs better than String IndexOf method          2000 characters in s1  search token in s2     string s1    Many characters  The quick brown fox jumps over the lazy dog        string s2    fox       bool b      b   s1 Contains s2       int i      i   s1 IndexOf s2     Fun fact

User · Accepted Answer

Contains calls IndexOf   public bool Contains string value        return  this IndexOf value  StringComparison Ordinal   gt   0       Which calls CompareInfo IndexOf  which ultimately uses a CLR implementation   If you want to see how strings are compared in the CLR this will show you  look for CaseInsensitiveCompHelper     IndexOf string  has no options and Contains  uses an Ordinal compare  a byte-by-byte comparison rather than trying to perform a smart compare  for example  e with       So IndexOf will be marginally faster  in theory  as IndexOf goes straight to a string search using FindNLSString from kernel32 dll  the power of reflector     Updated for  NET 4 0 - IndexOf no longer uses Ordinal Comparison and so Contains can be faster   See comment below

User · Answer

Probably  it will not matter at all  Read this post on Coding Horror     http   www codinghorror com blog archives 001218 html

User · Answer

Contains s2  is many times  in my computer 10 times  faster than IndexOf s2  because Contains uses StringComparison Ordinal that is faster than the culture sensitive search that IndexOf does by default  but that may change in  net 4 0 http   davesbox com archive 2008 11 12 breaking-changes-to-the-string-class aspx     Contains has exactly the same performance as IndexOf s2 StringComparison Ordinal     0 in my tests but it s shorter and makes your intent clear

User · Answer

If you really want to micro optimise your code your best approach is always benchmarking   The  net framework has an excellent stopwatch implementation - System Diagnostics Stopwatch

User · Answer

Tried it today on a 1 3 GB text file  Amongst others every line is checked for existence of a     char  17 000 000 calls to Contains IndexOf are made  Result  12 5 sec for all Contains      calls  2 5 sec for all IndexOf      calls    gt  IndexOf performs 5 times faster     Net 4 8

User · Answer

Just as an update to this I ve been doing some testing and providing your input string is fairly large then parallel Regex is the fastest C  method I ve found  providing you have more than one core I imagine   Getting the total amount of matches for example -  needles AsParallel     Sum   l   gt  Regex IsMatch   haystack   Regex Escape   l       1   0      Hope this helps

User · Answer

From a little reading  it appears that under the hood the String Contains method simply calls String IndexOf   The difference is String Contains returns a boolean while String IndexOf returns an integer with  -1  representing that the substring was not found     I would suggest writing a little test with 100 000 or so iterations and see for yourself   If I were to guess  I d say that IndexOf may be slightly faster but like I said it just a guess     Jeff Atwood has a good article on strings at his blog   It s more about concatenation but may be helpful nonetheless

User · Answer

If you really want to micro optimise your code your best approach is always benchmarking   The  net framework has an excellent stopwatch implementation - System Diagnostics Stopwatch

User · Answer

Contains s2  is many times  in my computer 10 times  faster than IndexOf s2  because Contains uses StringComparison Ordinal that is faster than the culture sensitive search that IndexOf does by default  but that may change in  net 4 0 http   davesbox com archive 2008 11 12 breaking-changes-to-the-string-class aspx     Contains has exactly the same performance as IndexOf s2 StringComparison Ordinal     0 in my tests but it s shorter and makes your intent clear

User · Answer

Probably  it will not matter at all  Read this post on Coding Horror     http   www codinghorror com blog archives 001218 html

User · Answer

Probably  it will not matter at all  Read this post on Coding Horror     http   www codinghorror com blog archives 001218 html

User · Answer

By using Reflector  you can see  that Contains is implemented using IndexOf  Here s the implementation   public bool Contains string value       return  this IndexOf value  StringComparison Ordinal   gt   0       So Contains is likely a wee bit slower than calling IndexOf directly  but I doubt that it will have any significance for the actual performance

User · Answer

For anyone still reading this  indexOf   will probably perform better on most enterprise systems  as contains   is not compatible with IE

User · Answer

Contains s2  is many times  in my computer 10 times  faster than IndexOf s2  because Contains uses StringComparison Ordinal that is faster than the culture sensitive search that IndexOf does by default  but that may change in  net 4 0 http   davesbox com archive 2008 11 12 breaking-changes-to-the-string-class aspx     Contains has exactly the same performance as IndexOf s2 StringComparison Ordinal     0 in my tests but it s shorter and makes your intent clear

User · Answer

Use a benchmark library  like this recent foray from Jon Skeet to measure it   Caveat Emptor  As all  micro- performance questions  this depends on the versions of software you are using  the details of the data inspected and the code surrounding the call   As all  micro- performance questions  the first step has to be to get a running version which is easily maintainable  Then benchmarking  profiling and tuning can be applied to the measured bottlenecks instead of guessing

User · Answer

If you really want to micro optimise your code your best approach is always benchmarking   The  net framework has an excellent stopwatch implementation - System Diagnostics Stopwatch

User · Answer

Use a benchmark library  like this recent foray from Jon Skeet to measure it   Caveat Emptor  As all  micro- performance questions  this depends on the versions of software you are using  the details of the data inspected and the code surrounding the call   As all  micro- performance questions  the first step has to be to get a running version which is easily maintainable  Then benchmarking  profiling and tuning can be applied to the measured bottlenecks instead of guessing

User · Answer

From a little reading  it appears that under the hood the String Contains method simply calls String IndexOf   The difference is String Contains returns a boolean while String IndexOf returns an integer with  -1  representing that the substring was not found     I would suggest writing a little test with 100 000 or so iterations and see for yourself   If I were to guess  I d say that IndexOf may be slightly faster but like I said it just a guess     Jeff Atwood has a good article on strings at his blog   It s more about concatenation but may be helpful nonetheless

User · Answer

For anyone still reading this  indexOf   will probably perform better on most enterprise systems  as contains   is not compatible with IE

User · Answer

I am running a real case  in opposite to a synthetic benchmark    if     lt     gt   lt  gt   lt   gt          IndexOf tmps  gt  0      versus   if     lt     gt   lt  gt   lt   gt          Contains tmps       It is a vital part of my system and it is executed 131 953 times  thanks DotTrace    However shocking surprise  the result is the opposite that expected   IndexOf 533ms  Contains 266ms     -   net framework 4 0   updated as for 13-02-2012

User · Answer

Use a benchmark library  like this recent foray from Jon Skeet to measure it   Caveat Emptor  As all  micro- performance questions  this depends on the versions of software you are using  the details of the data inspected and the code surrounding the call   As all  micro- performance questions  the first step has to be to get a running version which is easily maintainable  Then benchmarking  profiling and tuning can be applied to the measured bottlenecks instead of guessing

User · Answer

From a little reading  it appears that under the hood the String Contains method simply calls String IndexOf   The difference is String Contains returns a boolean while String IndexOf returns an integer with  -1  representing that the substring was not found     I would suggest writing a little test with 100 000 or so iterations and see for yourself   If I were to guess  I d say that IndexOf may be slightly faster but like I said it just a guess     Jeff Atwood has a good article on strings at his blog   It s more about concatenation but may be helpful nonetheless

User · Answer

By using Reflector  you can see  that Contains is implemented using IndexOf  Here s the implementation   public bool Contains string value       return  this IndexOf value  StringComparison Ordinal   gt   0       So Contains is likely a wee bit slower than calling IndexOf directly  but I doubt that it will have any significance for the actual performance

User · Answer

Contains s2  is many times  in my computer 10 times  faster than IndexOf s2  because Contains uses StringComparison Ordinal that is faster than the culture sensitive search that IndexOf does by default  but that may change in  net 4 0 http   davesbox com archive 2008 11 12 breaking-changes-to-the-string-class aspx     Contains has exactly the same performance as IndexOf s2 StringComparison Ordinal     0 in my tests but it s shorter and makes your intent clear

User · Answer

Tried it today on a 1 3 GB text file  Amongst others every line is checked for existence of a     char  17 000 000 calls to Contains IndexOf are made  Result  12 5 sec for all Contains      calls  2 5 sec for all IndexOf      calls    gt  IndexOf performs 5 times faster     Net 4 8

User · Answer

I am running a real case  in opposite to a synthetic benchmark    if     lt     gt   lt  gt   lt   gt          IndexOf tmps  gt  0      versus   if     lt     gt   lt  gt   lt   gt          Contains tmps       It is a vital part of my system and it is executed 131 953 times  thanks DotTrace    However shocking surprise  the result is the opposite that expected   IndexOf 533ms  Contains 266ms     -   net framework 4 0   updated as for 13-02-2012

User · Answer

From a little reading  it appears that under the hood the String Contains method simply calls String IndexOf   The difference is String Contains returns a boolean while String IndexOf returns an integer with  -1  representing that the substring was not found     I would suggest writing a little test with 100 000 or so iterations and see for yourself   If I were to guess  I d say that IndexOf may be slightly faster but like I said it just a guess     Jeff Atwood has a good article on strings at his blog   It s more about concatenation but may be helpful nonetheless

User · Answer

By using Reflector  you can see  that Contains is implemented using IndexOf  Here s the implementation   public bool Contains string value       return  this IndexOf value  StringComparison Ordinal   gt   0       So Contains is likely a wee bit slower than calling IndexOf directly  but I doubt that it will have any significance for the actual performance

User · Answer

By using Reflector  you can see  that Contains is implemented using IndexOf  Here s the implementation   public bool Contains string value       return  this IndexOf value  StringComparison Ordinal   gt   0       So Contains is likely a wee bit slower than calling IndexOf directly  but I doubt that it will have any significance for the actual performance

User · Answer

Probably  it will not matter at all  Read this post on Coding Horror     http   www codinghorror com blog archives 001218 html

User · Answer

If you really want to micro optimise your code your best approach is always benchmarking   The  net framework has an excellent stopwatch implementation - System Diagnostics Stopwatch

User · Answer

Just as an update to this I ve been doing some testing and providing your input string is fairly large then parallel Regex is the fastest C  method I ve found  providing you have more than one core I imagine   Getting the total amount of matches for example -  needles AsParallel     Sum   l   gt  Regex IsMatch   haystack   Regex Escape   l       1   0      Hope this helps

User · Answer

Use a benchmark library  like this recent foray from Jon Skeet to measure it   Caveat Emptor  As all  micro- performance questions  this depends on the versions of software you are using  the details of the data inspected and the code surrounding the call   As all  micro- performance questions  the first step has to be to get a running version which is easily maintainable  Then benchmarking  profiling and tuning can be applied to the measured bottlenecks instead of guessing

[c#] Is String.Contains() faster than String.IndexOf()?

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