Is there a way to make the following return true?
string title = "ASTRINGTOTEST";
title.Contains("string");
There doesn't seem to be an overload that allows me to set the case sensitivity.. Currently I UPPERCASE them both, but that's just silly (by which I am referring to the i18n issues that come with up- and down casing).
UPDATE
This question is ancient and since then I have realized I asked for a simple answer for a really vast and difficult topic if you care to investigate it fully.
For most cases, in mono-lingual, English code bases this answer will suffice. I'm suspecting because most people coming here fall in this category this is the most popular answer.
This answer however brings up the inherent problem that we can't compare text case insensitive until we know both texts are the same culture and we know what that culture is. This is maybe a less popular answer, but I think it is more correct and that's why I marked it as such.
You could use the String.IndexOf Method and pass StringComparison.OrdinalIgnoreCase as the type of search to use:
string title = "STRING";
bool contains = title.IndexOf("string", StringComparison.OrdinalIgnoreCase) >= 0;
Even better is defining a new extension method for string:
public static class StringExtensions
{
public static bool Contains(this string source, string toCheck, StringComparison comp)
{
return source?.IndexOf(toCheck, comp) >= 0;
}
}
Note, that null propagation ?. is available since C# 6.0 (VS 2015), for older versions use
if (source == null) return false;
return source.IndexOf(toCheck, comp) >= 0;
USAGE:
string title = "STRING";
bool contains = title.Contains("string", StringComparison.OrdinalIgnoreCase);
JaredPar
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.
Colonel Panic
You can use IndexOf() like this:
string title = "STRING";
if (title.IndexOf("string", 0, StringComparison.CurrentCultureIgnoreCase) != -1)
{
// The string exists in the original
}
Since 0 (zero) can be an index, you check against -1.
MSDN
The zero-based index position of value if that string is found, or -1
if it is not. If value is String.Empty, the return value is 0.
mkchandler
Alternative solution using Regex:
bool contains = Regex.IsMatch("StRiNG to search", Regex.Escape("string"), RegexOptions.IgnoreCase);
Jed
.NET Core 2.0+ (including .NET 5.0+)
.NET Core has had a pair of methods to deal with this since version 2.0 :
- String.Contains(Char, StringComparison)
- String.Contains(String, StringComparison)
Example:
"Test".Contains("test", System.StringComparison.CurrentCultureIgnoreCase);
It is now officially part of the .NET Standard 2.1, and therefore part of all the implementations of the Base Class Library that implement this version of the standard (or a higher one).
Mathieu Renda
You could always just up or downcase the strings first.
string title = "string":
title.ToUpper().Contains("STRING") // returns true
Oops, just saw that last bit. A case insensitive compare would *probably* do the same anyway, and if performance is not an issue, I don't see a problem with creating uppercase copies and comparing those. I could have sworn that I once saw a case-insensitive compare once...
Ed S.
One issue with the answer is that it will throw an exception if a string is null. You can add that as a check so it won't:
public static bool Contains(this string source, string toCheck, StringComparison comp)
{
if (string.IsNullOrEmpty(toCheck) || string.IsNullOrEmpty(source))
return true;
return source.IndexOf(toCheck, comp) >= 0;
}
FeiBao 飞豹
StringExtension class is the way forward, I've combined a couple of the posts above to give a complete code example:
public static class StringExtensions
{
/// <summary>
/// Allows case insensitive checks
/// </summary>
public static bool Contains(this string source, string toCheck, StringComparison comp)
{
return source.IndexOf(toCheck, comp) >= 0;
}
}
Andrew
This is clean and simple.
Regex.IsMatch(file, fileNamestr, RegexOptions.IgnoreCase)
takirala
OrdinalIgnoreCase, CurrentCultureIgnoreCase or InvariantCultureIgnoreCase?
Since this is missing, here are some recommendations about when to use which one:
Dos
- Use
StringComparison.OrdinalIgnoreCase for comparisons
as your safe default for culture-agnostic string matching.
- Use
StringComparison.OrdinalIgnoreCase comparisons
for increased speed.
- Use
StringComparison.CurrentCulture-based string operations
when displaying the output to the user.
- Switch current use of string operations based on the invariant
culture to use the non-linguistic
StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase when the comparison is
linguistically irrelevant (symbolic, for example).
- Use
ToUpperInvariant rather than ToLowerInvariant when
normalizing strings for comparison.
Don'ts
- Use overloads for string operations that don't explicitly
or implicitly specify the string comparison mechanism.
- Use
StringComparison.InvariantCulture -based string
operations in most cases; one of the few exceptions would be
persisting linguistically meaningful but culturally-agnostic data.
Based on these rules you should use:
string title = "STRING";
if (title.IndexOf("string", 0, StringComparison.[YourDecision]) != -1)
{
// The string exists in the original
}
whereas [YourDecision] depends on the recommendations from above.
link of source: http://msdn.microsoft.com/en-us/library/ms973919.aspx
Fabian Bigler
These are the easiest solutions.
By Index of
string title = "STRING";
if (title.IndexOf("string", 0, StringComparison.CurrentCultureIgnoreCase) != -1)
{
// contains
}
By Changing case
string title = "STRING";
bool contains = title.ToLower().Contains("string")
By Regex
Regex.IsMatch(title, "string", RegexOptions.IgnoreCase);
LAV VISHWAKARMA
As simple and works
title.ToLower().Contains("String".ToLower())
Pradeep Asanka
Just like this:
string s="AbcdEf";
if(s.ToLower().Contains("def"))
{
Console.WriteLine("yes");
}
cdytoby
I know that this is not the C#, but in the framework (VB.NET) there is already such a function
Dim str As String = "UPPERlower"
Dim b As Boolean = InStr(str, "UpperLower")
C# variant:
string myString = "Hello World";
bool contains = Microsoft.VisualBasic.Strings.InStr(myString, "world");
serhio
The InStr method from the VisualBasic assembly is the best if you have a concern about internationalization (or you could reimplement it). Looking at in it dotNeetPeek shows that not only does it account for caps and lowercase, but also for kana type and full- vs. half-width characters (mostly relevant for Asian languages, although there are full-width versions of the Roman alphabet too). I'm skipping over some details, but check out the private method InternalInStrText:
private static int InternalInStrText(int lStartPos, string sSrc, string sFind)
{
int num = sSrc == null ? 0 : sSrc.Length;
if (lStartPos > num || num == 0)
return -1;
if (sFind == null || sFind.Length == 0)
return lStartPos;
else
return Utils.GetCultureInfo().CompareInfo.IndexOf(sSrc, sFind, lStartPos, CompareOptions.IgnoreCase | CompareOptions.IgnoreKanaType | CompareOptions.IgnoreWidth);
}
Casey
Use this:
string.Compare("string", "STRING", new System.Globalization.CultureInfo("en-US"), System.Globalization.CompareOptions.IgnoreCase);
mr.martan
You can use a string comparison parameter (available from .net 2.1 and above) String.Contains Method.
public bool Contains (string value, StringComparison comparisonType);
Example:
string title = "ASTRINGTOTEST";
title.Contains("string", StringComparison.InvariantCultureIgnoreCase);
dashrader
This is quite similar to other example here, but I've decided to simplify enum to bool, primary because other alternatives are normally not needed. Here is my example:
public static class StringExtensions
{
public static bool Contains(this string source, string toCheck, bool bCaseInsensitive )
{
return source.IndexOf(toCheck, bCaseInsensitive ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal) >= 0;
}
}
And usage is something like:
if( "main String substring".Contains("SUBSTRING", true) )
....
TarmoPikaro
Using a RegEx is a straight way to do this:
Regex.IsMatch(title, "string", RegexOptions.IgnoreCase);
Stend
Just to build on the answer here, you can create a string extension method to make this a little more user-friendly:
public static bool ContainsIgnoreCase(this string paragraph, string word)
{
return CultureInfo.CurrentCulture.CompareInfo.IndexOf(paragraph, word, CompareOptions.IgnoreCase) >= 0;
}
Christian Findlay
if you want to check if your passed string is in string then there is a simple method for that.
string yourStringForCheck= "abc";
string stringInWhichWeCheck= "Test abc abc";
bool isContained = stringInWhichWeCheck.ToLower().IndexOf(yourStringForCheck.ToLower()) > -1;
This boolean value will return if the string is contained or not
shaishav shukla
Similar to previous answers (using an extension method) but with two simple null checks (C# 6.0 and above):
public static bool ContainsIgnoreCase(this string source, string substring)
{
return source?.IndexOf(substring ?? "", StringComparison.OrdinalIgnoreCase) >= 0;
}
If source is null, return false (via null-propagation operator ?.)
If substring is null, treat as an empty string and return true (via null-coalescing operator ??)
The StringComparison can of course be sent as a parameter if needed.
Udi Y
if ("strcmpstring1".IndexOf(Convert.ToString("strcmpstring2"), StringComparison.CurrentCultureIgnoreCase) >= 0){return true;}else{return false;}
Tamilselvan K
You can use string.indexof () function. This will be case insensitive
Okan SARICA
The trick here is to look for the string, ignoring case, but to keep it exactly the same (with the same case).
var s="Factory Reset";
var txt="reset";
int first = s.IndexOf(txt, StringComparison.InvariantCultureIgnoreCase) + txt.Length;
var subString = s.Substring(first - txt.Length, txt.Length);
Output is "Reset"
Mr.B
public static class StringExtension
{
#region Public Methods
public static bool ExContains(this string fullText, string value)
{
return ExIndexOf(fullText, value) > -1;
}
public static bool ExEquals(this string text, string textToCompare)
{
return text.Equals(textToCompare, StringComparison.OrdinalIgnoreCase);
}
public static bool ExHasAllEquals(this string text, params string[] textArgs)
{
for (int index = 0; index < textArgs.Length; index++)
if (ExEquals(text, textArgs[index]) == false) return false;
return true;
}
public static bool ExHasEquals(this string text, params string[] textArgs)
{
for (int index = 0; index < textArgs.Length; index++)
if (ExEquals(text, textArgs[index])) return true;
return false;
}
public static bool ExHasNoEquals(this string text, params string[] textArgs)
{
return ExHasEquals(text, textArgs) == false;
}
public static bool ExHasNotAllEquals(this string text, params string[] textArgs)
{
for (int index = 0; index < textArgs.Length; index++)
if (ExEquals(text, textArgs[index])) return false;
return true;
}
/// <summary>
/// Reports the zero-based index of the first occurrence of the specified string
/// in the current System.String object using StringComparison.InvariantCultureIgnoreCase.
/// A parameter specifies the type of search to use for the specified string.
/// </summary>
/// <param name="fullText">
/// The string to search inside.
/// </param>
/// <param name="value">
/// The string to seek.
/// </param>
/// <returns>
/// The index position of the value parameter if that string is found, or -1 if it
/// is not. If value is System.String.Empty, the return value is 0.
/// </returns>
/// <exception cref="ArgumentNullException">
/// fullText or value is null.
/// </exception>
public static int ExIndexOf(this string fullText, string value)
{
return fullText.IndexOf(value, StringComparison.OrdinalIgnoreCase);
}
public static bool ExNotEquals(this string text, string textToCompare)
{
return ExEquals(text, textToCompare) == false;
}
#endregion Public Methods
}
Final Heaven
Based on the existing answers and on the documentation of Contains method I would recommend the creation of the following extension which also takes care of the corner cases:
public static class VStringExtensions
{
public static bool Contains(this string source, string toCheck, StringComparison comp)
{
if (toCheck == null)
{
throw new ArgumentNullException(nameof(toCheck));
}
if (source.Equals(string.Empty))
{
return false;
}
if (toCheck.Equals(string.Empty))
{
return true;
}
return source.IndexOf(toCheck, comp) >= 0;
}
}
Valentin Peta
Simple way for newbie:
title.ToLower().Contains("string");//of course "string" is lowercase.
O Thạnh LdtRetrieved from : http:www.stackoverflow.com/questions/444798/case-insensitive-containsstring