Contains Case Insensitive

Case insensitive 'Contains(string)'

To test if the string paragraph contains the string word (thanks @QuarterMeister)

culture.CompareInfo.IndexOf(paragraph, word, CompareOptions.IgnoreCase) >= 0

Where culture is the instance of CultureInfo describing the language that the text is written in.

This solution is transparent about the definition of case-insensitivity, which is language dependent. For example, the English language uses the characters I and i for the upper and lower case versions of the ninth letter, whereas the Turkish language uses these characters for the eleventh and twelfth letters of its 29 letter-long alphabet. The Turkish upper case version of 'i' is the unfamiliar character 'İ'.

Thus the strings tin and TIN are the same word in English, but different words in Turkish. As I understand, one means 'spirit' and the other is an onomatopoeia word. (Turks, please correct me if I'm wrong, or suggest a better example)

To summarise, you can only answer the question 'are these two strings the same but in different cases' if you know what language the text is in. If you don't know, you'll have to take a punt. Given English's hegemony in software, you should probably resort to CultureInfo.InvariantCulture, because it will be wrong in familiar ways.

Contains case insensitive

Add .toUpperCase() after referrer. This method turns the string into an upper case string. Then, use .indexOf() using RAL instead of Ral.

if (referrer.toUpperCase().indexOf("RAL") === -1) { 

The same can also be achieved using a Regular Expression (especially useful when you want to test against dynamic patterns):

if (!/Ral/i.test(referrer)) {
   //    ^i = Ignore case flag for RegExp

How to check if a String contains another String in a case insensitive manner in Java?

Yes, contains is case sensitive. You can use java.util.regex.Pattern with the CASE_INSENSITIVE flag for case insensitive matching:

Pattern.compile(Pattern.quote(wantedStr), Pattern.CASE_INSENSITIVE).matcher(source).find();

EDIT: If s2 contains regex special characters (of which there are many) it's important to quote it first. I've corrected my answer since it is the first one people will see, but vote up Matt Quail's since he pointed this out.

Make String.Contains() case insensitive

If x.IndexOf(y, StringComparison.CurrentCultureIgnoreCase) >= 0 Then
    'do nothing
End If

c# contains case insensitive search

1. You can use ToLower() function. ToLower changes strings to be all lowercase. It converts an entire string—without changing letters that are already lowercased or digits. It copies a string and returns a reference to the new string. So it is always better option to declare criteria.Author.ToLower() outside the query.

   string lowerAuthor = criteria.Author.ToLower();
   returnData = returnData.Where
           (x => x.Author.ToLower().Contains(lowerAuthor));
   

2. You could also use IndexOfoverload with the StringComparison enum. It would give you better performance than ToLower(). The signature of this overload is:

   int string.IndexOf(string value, StringComparison comparisonType);
   

   ---

   returnData = returnData.Where
       (x => x.Author.IndexOf(criteria.Author, StringComparison.CurrentCultureIgnoreCase) != -1);
   

javascript includes() case insensitive

You can create a RegExp from filterstrings first

var filterstrings = ['firststring','secondstring','thridstring'];
var regex = new RegExp( filterstrings.join( "|" ), "i");

then test if the passedinstring is there

var isAvailable = regex.test( passedinstring ); 

String contains - ignore case

You can use

org.apache.commons.lang3.StringUtils.containsIgnoreCase(CharSequence str,
                                     CharSequence searchStr);

Checks if CharSequence contains a search CharSequence irrespective of
case, handling null. Case-insensitivity is defined as by
String.equalsIgnoreCase(String).

A null CharSequence will return false.

This one will be better than regex as regex is always expensive in terms of performance.

For official doc, refer to : StringUtils.containsIgnoreCase

Update :

If you are among the ones who

• don't want to use Apache commons library
• don't want to go with the expensive regex/Pattern based solutions,
• don't want to create additional string object by using toLowerCase,

you can implement your own custom containsIgnoreCase using java.lang.String.regionMatches

public boolean regionMatches(boolean ignoreCase,
                             int toffset,
                             String other,
                             int ooffset,
                             int len)

ignoreCase : if true, ignores case when comparing characters.

public static boolean containsIgnoreCase(String str, String searchStr)     {
    if(str == null || searchStr == null) return false;

    final int length = searchStr.length();
    if (length == 0)
        return true;

    for (int i = str.length() - length; i >= 0; i--) {
        if (str.regionMatches(true, i, searchStr, 0, length))
            return true;
    }
    return false;
}

How do I make contains case-insensitive in ef core 2?

starting from version 2.1 of the EF Core, you can use HasConversion(). But the information in the database will be stored in lowercase:

builder.Property(it => it.Email).HasConversion(v => v.ToLowerInvariant(), v => v);

I solved a similar problem. This change solved all my problems.

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