CaseInsensitiveComparer.cs

Go to the documentation of this file.

using System.Globalization;
 
namespace System.Collections;
 
public class CaseInsensitiveComparer : IComparer
{
    private readonly CompareInfo _compareInfo;
 
    private static volatile CaseInsensitiveComparer s_InvariantCaseInsensitiveComparer;
 
    public static CaseInsensitiveComparer Default => new CaseInsensitiveComparer(CultureInfo.CurrentCulture);
 
    public static CaseInsensitiveComparer DefaultInvariant
    {
        get
        {
            if (s_InvariantCaseInsensitiveComparer == null)
            {
                s_InvariantCaseInsensitiveComparer = new CaseInsensitiveComparer(CultureInfo.InvariantCulture);
            }
            return s_InvariantCaseInsensitiveComparer;
        }
    }
 
    public CaseInsensitiveComparer()
    {
        _compareInfo = CultureInfo.CurrentCulture.CompareInfo;
    }
 
    public CaseInsensitiveComparer(CultureInfo culture)
    {
        if (culture == null)
        {
            throw new ArgumentNullException("culture");
        }
        _compareInfo = culture.CompareInfo;
    }
 
    public int Compare(object? a, object? b)
    {
        string text = a as string;
        string text2 = b as string;
        if (text != null && text2 != null)
        {
            return _compareInfo.Compare(text, text2, CompareOptions.IgnoreCase);
        }
        return Comparer.Default.Compare(a, b);
    }
}