Is there a C# case insensitive equals operator?

Try this:

string.Equals(a, b, StringComparison.CurrentCultureIgnoreCase);

The best way to compare 2 strings ignoring the case of the letters is to use the String.Equals static method specifying an ordinal ignore case string comparison. This is also the fastest way, much faster than converting the strings to lower or upper case and comparing them after that.

I tested the performance of both approaches and the ordinal ignore case string comparison was more than 9 times faster! It is also more reliable than converting strings to lower or upper case (check out the Turkish i problem). So always use the String.Equals method to compare strings for equality:

String.Equals(string1, string2, StringComparison.OrdinalIgnoreCase);

If you want to perform a culture specific string comparison you can use the following code:

String.Equals(string1, string2, StringComparison.CurrentCultureIgnoreCase);

Please note that the second example uses the the string comparison logic of the current culture, which makes it slower than the "ordinal ignore case" comparison in the first example, so if you don't need any culture specific string comparison logic and you are after maximum performance, use the "ordinal ignore case" comparison.

For more information, read the full story on my blog.

There are a number of properties on the StringComparer static class that return comparers for any type of case-sensitivity you might want:

StringComparer Properties

For instance, you can call

StringComparer.CurrentCultureIgnoreCase.Equals(string1, string2)

or

StringComparer.CurrentCultureIgnoreCase.Compare(string1, string2)

It's a bit cleaner than the string.Equals or string.Compare overloads that take a StringComparison argument.