Comparer.cs

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using System.Globalization;
using System.Runtime.CompilerServices;
using System.Runtime.Serialization;
 
namespace System.Collections;
 
[Serializable]
[TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
public sealed class Comparer : IComparer, ISerializable
{
    private readonly CompareInfo _compareInfo;
 
    public static readonly Comparer Default = new Comparer(CultureInfo.CurrentCulture);
 
    public static readonly Comparer DefaultInvariant = new Comparer(CultureInfo.InvariantCulture);
 
    public Comparer(CultureInfo culture)
    {
        if (culture == null)
        {
            throw new ArgumentNullException("culture");
        }
        _compareInfo = culture.CompareInfo;
    }
 
    private Comparer(SerializationInfo info, StreamingContext context)
    {
        if (info == null)
        {
            throw new ArgumentNullException("info");
        }
        _compareInfo = (CompareInfo)info.GetValue("CompareInfo", typeof(CompareInfo));
    }
 
    public void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        if (info == null)
        {
            throw new ArgumentNullException("info");
        }
        info.AddValue("CompareInfo", _compareInfo);
    }
 
    public int Compare(object? a, object? b)
    {
        if (a == b)
        {
            return 0;
        }
        if (a == null)
        {
            return -1;
        }
        if (b == null)
        {
            return 1;
        }
        if (a is string @string && b is string string2)
        {
            return _compareInfo.Compare(@string, string2);
        }
        if (a is IComparable comparable)
        {
            return comparable.CompareTo(b);
        }
        if (b is IComparable comparable2)
        {
            return -comparable2.CompareTo(a);
        }
        throw new ArgumentException(SR.Argument_ImplementIComparable);
    }
}