EqualityComparer.cs

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using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
 
namespace System.Collections.Generic;
 
[Serializable]
[TypeDependency("System.Collections.Generic.ObjectEqualityComparer`1")]
[TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
public abstract class EqualityComparer<T> : IEqualityComparer, IEqualityComparer<T>
{
    public static EqualityComparer<T> Default
    {
        [Intrinsic]
        get;
    } = (EqualityComparer<T>)ComparerHelpers.CreateDefaultEqualityComparer(typeof(T));
 
 
    public abstract bool Equals(T? x, T? y);
 
    public abstract int GetHashCode([DisallowNull] T obj);
 
    int IEqualityComparer.GetHashCode(object obj)
    {
        if (obj == null)
        {
            return 0;
        }
        if (obj is T)
        {
            return GetHashCode((T)obj);
        }
        ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArgumentForComparison);
        return 0;
    }
 
    bool IEqualityComparer.Equals(object x, object y)
    {
        if (x == y)
        {
            return true;
        }
        if (x == null || y == null)
        {
            return false;
        }
        if (x is T && y is T)
        {
            return Equals((T)x, (T)y);
        }
        ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArgumentForComparison);
        return false;
    }
 
    internal virtual int IndexOf(T[] array, T value, int startIndex, int count)
    {
        int num = startIndex + count;
        for (int i = startIndex; i < num; i++)
        {
            if (Equals(array[i], value))
            {
                return i;
            }
        }
        return -1;
    }
 
    internal virtual int LastIndexOf(T[] array, T value, int startIndex, int count)
    {
        int num = startIndex - count + 1;
        for (int num2 = startIndex; num2 >= num; num2--)
        {
            if (Equals(array[num2], value))
            {
                return num2;
            }
        }
        return -1;
    }
}