Case Insensitive comparison in C# [duplicate]

Answer 1

I prefer an extension method like this.

public static class StringExtensions
{
    public static bool Contains(this string source, string value, StringComparison compareMode)
    {
        if (string.IsNullOrEmpty(source))
            return false;

        return source.IndexOf(value, compareMode) >= 0;
    }
}

Notice that in this way you could avoid the costly transformation in upper or lower case.

You could call the extension using this syntax

 bool result = "This is a try".Contains("TRY", StringComparison.InvariantCultureIgnoreCase);
 Console.WriteLine(result);

Please note: the above extension (as true for every extension method) should be defined inside a non-nested, non-generic static class See MSDN Ref