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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
/*============================================================
**
** Purpose: Default IComparer implementation.
**
===========================================================*/
using System.Globalization;
using System.Runtime.Serialization;
namespace System.Collections
{
[Serializable]
[System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
public sealed class Comparer : IComparer, ISerializable
{
private 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(nameof(culture));
_compareInfo = culture.CompareInfo;
}
private Comparer(SerializationInfo info, StreamingContext context)
{
if (info == null)
throw new ArgumentNullException(nameof(info));
_compareInfo = (CompareInfo)info.GetValue("CompareInfo", typeof(CompareInfo));
}
public void GetObjectData(SerializationInfo info, StreamingContext context)
{
if (info == null)
throw new ArgumentNullException(nameof(info));
info.AddValue("CompareInfo", _compareInfo);
}
// Compares two Objects by calling CompareTo.
// If a == b, 0 is returned.
// If a implements IComparable, a.CompareTo(b) is returned.
// If a doesn't implement IComparable and b does, -(b.CompareTo(a)) is returned.
// Otherwise an exception is thrown.
//
public int Compare(Object a, Object b)
{
if (a == b) return 0;
if (a == null) return -1;
if (b == null) return 1;
string sa = a as string;
string sb = b as string;
if (sa != null && sb != null)
return _compareInfo.Compare(sa, sb);
IComparable ia = a as IComparable;
if (ia != null)
return ia.CompareTo(b);
IComparable ib = b as IComparable;
if (ib != null)
return -ib.CompareTo(a);
throw new ArgumentException(SR.Argument_ImplementIComparable);
}
}
}
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