您可以创建一个通用的比较器,该比较器接受一个委托以选择关键字:
class ByKeyComparer<T, TKey> : IComparer<T>
{
private readonly Func<T, TKey> _keySelector;
private readonly IComparer<TKey> _keyComparer;
public ByKeyComparer(Func<T, TKey> keySelector, IComparer<TKey> keyComparer = null)
{
if (keySelector == null) throw new ArgumentNullException("keySelector");
_keySelector = keySelector;
_keyComparer = keyComparer ?? Comparer<TKey>.Default;
}
public int Compare(T x, T y)
{
return _keyComparer.Compare(_keySelector(x), _keySelector(y));
}
}
使用一个助手类来利用类型推断(这样你就不需要指定键的类型):
static class ByKeyComparer<T>
{
public static IComparer<T> Create<TKey>(Func<T, TKey> keySelector, IComparer<TKey> keyComparer = null)
{
return new ByKeyComparer<T, TKey>(keySelector, keyComparer);
}
}
您可以像这样使用它:
var patchVersionComparer = ByKeyComparer<Patch>.Create(p => p.Version)
patches.Sort(patchVersionComparer)
如果您需要组合多个比较键,可以创建一个使用其他比较器的比较器:
class CompositeComparer<T> : IComparer<T>
{
private readonly IEnumerable<IComparer<T>> _comparers;
public CompositeComparer(IEnumerable<IComparer<T>> comparers)
{
if (comparers == null) throw new ArgumentNullException("comparers");
_comparers = comparers;
}
public CompositeComparer(params IComparer<T>[] comparers)
: this((IEnumerable<IComparer<T>>)comparers)
{
}
public int Compare(T x, T y)
{
foreach (var comparer in _comparers)
{
int result = comparer.Compare(x, y);
if (result != 0)
return result;
}
return 0;
}
}
示例用法:
var comparer = new CompositeComparer<Patch>(
ByKeyComparer<Patch>.Create(p => p.Key1),
ByKeyComparer<Patch>.Create(p => p.Key2),
ByKeyComparer<Patch>.Create(p => p.Key3));
patches.Sort(comparer);
编辑:这里有一个更流畅的API:
static class ByKeyComparer<T>
{
public static IComparer<T> CompareBy<TKey>(Func<T, TKey> keySelector, IComparer<TKey> keyComparer = null)
{
return new ByKeyComparer<T, TKey>(keySelector, keyComparer);
}
}
static class ComparerExtensions
{
public static IComparer<T> ThenBy<T, TKey>(this IComparer<T> comparer, Func<T, TKey> keySelector, IComparer<TKey> keyComparer = null)
{
var newComparer = ByKeyComparer<T>.CompareBy(keySelector, keyComparer);
var composite = comparer as CompositeComparer<T>;
if (composite != null)
return new CompositeComparer<T>(composite.Comparers.Concat(new[] { newComparer }));
return new CompositeComparer<T>(comparer, newComparer);
}
}
例子:
var comparer = ByKeyComparer<Patch>.CompareBy(p => p.Key1)
.ThenBy(p => p.Key2)
.ThenBy(p => p.Key3)
patches.Sort(comparer)
(显然,您可能希望添加*Descending
版本的CompareBy
和ThenBy
方法,以允许按降序排序)