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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.Diagnostics.Contracts;
namespace System.Collections
{
internal sealed class Comparer : IComparer
{
private CompareInfo m_compareInfo;
public static readonly Comparer Default = new Comparer(CultureInfo.CurrentCulture);
public static readonly Comparer DefaultInvariant = new Comparer(CultureInfo.InvariantCulture);
private Comparer()
{
m_compareInfo = null;
}
public Comparer(CultureInfo culture)
{
if (culture == null)
{
throw new ArgumentNullException(nameof(culture));
}
Contract.EndContractBlock();
m_compareInfo = culture.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;
if (m_compareInfo != null)
{
String sa = a as String;
String sb = b as String;
if (sa != null && sb != null)
return m_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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