ComparisonHelper.cs
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using NCC.Dependency;
using System;
using System.Collections.Generic;
namespace NCC.Common.Helper
{
/// <summary>
/// 比较器辅助类，用于快速创建<see cref="IComparer{T}"/>接口的实例
/// </summary>
/// <example>
/// var comparer1 = Comparison[Person].CreateComparer(p => p.ID); var comparer2 = Comparison[Person].CreateComparer(p => p.Name); var comparer3 = Comparison[Person].CreateComparer(p => p.Birthday.Year)
/// </example>
/// <typeparam name="T">要比较的类型</typeparam>
[SuppressSniffer]
public static class ComparisonHelper<T>
{
/// <summary>
/// 创建指定对比委托<paramref name="keySelector"/>的实例
/// </summary>
public static IComparer<T> CreateComparer<TV>(Func<T, TV> keySelector)
{
return new CommonComparer<TV>(keySelector);
}
/// <summary>
/// 创建指定对比委托<paramref name="keySelector"/>与结果二次比较器<paramref name="comparer"/>的实例
/// </summary>
public static IComparer<T> CreateComparer<TV>(Func<T, TV> keySelector, IComparer<TV> comparer)
{
return new CommonComparer<TV>(keySelector, comparer);
}
private class CommonComparer<TV> : IComparer<T>
{
private readonly IComparer<TV> _comparer;
private readonly Func<T, TV> _keySelector;
public CommonComparer(Func<T, TV> keySelector, IComparer<TV> comparer)
{
_keySelector = keySelector;
_comparer = comparer;
}
public CommonComparer(Func<T, TV> keySelector)
: this(keySelector, Comparer<TV>.Default)
{ }
public int Compare(T x, T y)
{
return _comparer.Compare(_keySelector(x), _keySelector(y));
}
}
}
}