How Can I Perform a Case-Insensitive String Contains Check in C#?

Case-Insensitive String Matching in C#

C#'s built-in Contains() method is case-sensitive. To perform a case-insensitive check for substring presence, you'll need a different approach. The IndexOf() method offers a solution using the StringComparison.OrdinalIgnoreCase option:

<code class="language-csharp">string title = "STRING";
bool contains = title.IndexOf("string", StringComparison.OrdinalIgnoreCase) >= 0;</code>

This explicitly defines the comparison type. For cleaner code, an extension method provides a more intuitive solution:

<code class="language-csharp">public static class StringExtensions
{
    public static bool ContainsIgnoreCase(this string source, string toCheck)
    {
        return source?.IndexOf(toCheck, StringComparison.OrdinalIgnoreCase) >= 0;
    }
}</code>

Now, case-insensitive checks are straightforward:

<code class="language-csharp">string title = "STRING";
bool contains = title.ContainsIgnoreCase("string");</code>

This extension method enhances readability and simplifies case-insensitive string comparisons, particularly beneficial when working with text where capitalization might vary.

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