Case insensitive 'Contains(string)'

Question

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.

Answer 1

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.

Answer 2

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

Answer 3

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"

Answer 4

These are the easiest solutions.

1. By Index of

   string title = "STRING";
   
   if (title.IndexOf("string", 0, StringComparison.CurrentCultureIgnoreCase) != -1)
   {
       // contains 
   }
   

2. By Changing case

   string title = "STRING";
   
   bool contains = title.ToLower().Contains("string")
   

3. By Regex

   Regex.IsMatch(title, "string", RegexOptions.IgnoreCase);
   

Answer 5

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) )
....

Answer 6

This is clean and simple.

Regex.IsMatch(file, fileNamestr, RegexOptions.IgnoreCase)