Comparing two strings ignoring case in C

Question

Which of the following two is more efficient   Or maybe is there a third option that s better still    string val    AStringValue    if  val Equals  astringvalue   StringComparison InvariantCultureIgnoreCase     OR  if  val ToLowerCase       astringvalue

User · Answer

My general answer to this kind of question on "efficiency" is almost always, which ever version of the code is most readable, is the most efficient.

That being said, I think (val.ToLowerCase() == "astringvalue") is pretty understandable at a glance by most people.

The efficience I refer to is not necesseraly in the execution of the code but rather in the maintanance and generally readability of the code in question.

User · Answer

The first one is the correct one  and IMHO the more efficient one  since the second  solution  instantiates a new string instance

User · Answer

The former is fastest  Turns out that val is immutable  and so a new string object is created with String ToLowerCase    rather than just direct comparison with the string comparer  Creating a new string object can be costly if you re doing this many times a second

User · Answer

1st is more efficient  and the best possible option  because val ToLowerCase   creates a new object since Strings are immutable

User · Answer

If you re looking for efficiency  use this   string Equals val   astringvalue   StringComparison OrdinalIgnoreCase    Ordinal comparisons can be significantly faster than culture-aware comparisons   ToLowerCase can be the better option if you re doing a lot of comparisons against the same string  however   As with any performance optimization  measure it  then decide

User · Answer

The  ToLowerCase version is not going to be faster - it involves an extra string allocation  which must later be collected   etc   Personally  I d use  string Equals val   astringvalue    StringComparison OrdinalIgnoreCase    this avoids all the issues of culture-sensitive strings  but as a consequence it avoids all the issues of culture-sensitive strings  Only you know whether that is OK in your context   Using the string Equals static method avoids any issues with val being null

User · Answer

you may also want to look at that already answered question  Differences in string compare methods in C

User · Answer

I d venture that the safest is to use String Equals to mitigate against the possibility that val is null

[c#] Comparing two strings, ignoring case in C#

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