Linq to Objects - 从数字列表中返回数字对

var nums = new[]{ 1, 2, 3, 4, 5, 6, 7};
var pairs  = /* some linq magic here*/ ;

=> 对 = { {1, 2}, {3, 4}, {5, 6}, {7, 0} }

的要素pairs应该是二元素列表，或者是带有两个字段的匿名类的实例，比如new {First = 1, Second = 2}.

默认的 linq 方法都无法通过一次扫描来延迟执行此操作。压缩序列本身会进行两次扫描，并且分组并不完全是懒惰的。最好的选择是直接实现它：

public static IEnumerable<T[]> Partition<T>(this IEnumerable<T> sequence, int partitionSize) {
    Contract.Requires(sequence != null)
    Contract.Requires(partitionSize > 0)

    var buffer = new T[partitionSize];
    var n = 0;
    foreach (var item in sequence) {
        buffer[n] = item;
        n += 1;
        if (n == partitionSize) {
            yield return buffer;
            buffer = new T[partitionSize];
            n = 0;
        }
    }
    //partial leftovers
    if (n > 0) yield return buffer;
}