如何使用Lambda或Linq语句执行以下操作？

Question

我有这个函数需要转换为lambda语句:

public int someFunction()
{
    int pCount = 0;
    foreach (Top top in Tops)
    {
        foreach (P p in top.TopPs)
        {
            pCount++;
        }
    }
    return pCount;
}

添加更多清晰度:

Tops和top.TopPs扩展了ObservableCollection

我该怎么做？

Answer 1

int count = Tops.Sum(top => top.TopPs.Count());

Answer 2

你的意思是LINQ查询？

int count = Tops.SelectMany(x => x.TopPs).Count();