趣味编程（一）

public T MaxElement<T, TCompare>(this IEnumerable<T> collection, Func<T, TCompare> func) where TCompare : IComparable<TCompare>
{
    T maxItem = default(T);
    TCompare maxValue = default(TCompare);
    foreach (var item in collection) {
        TCompare temp = func(item);
        if (maxItem == null || temp.CompareTo(maxValue) > 0) {
            maxValue = temp;
            maxItem = item;
        }
    }
    return maxItem;
}

string findStr = "Beijing";
var rm = findStr.ToCharArray().GroupBy(c => c).Select(g => new { g.Key, Count = g.Count() }).MaxElement(r => r.Count);

2、需求：生成不重复的随机数并排序。

public IList<int> GetRandoms(int min, int max, int length)
{
    IList<int> rlist = new List<int>();
    int index = 1;
    int seed = 0;
    while (index < length) {
        var random = new Random(seed++).Next(min, max);
        if (!rlist.Contains(random))
            rlist.Add(random);
        index = rlist.Count();
    }

    return rlist;
}

List<int> rlist = GetRandoms(10, 99, 20).ToList();
rlist.Sort((x, y) => Math.Sign(x - y));