Count the number of elements in a list of lists with Linq

Question

I'd like to use some LINQ in my C# code to improve readability.

Given

private IDictionary<T, ICollection<E>> myDict;

a Dictionary with collections as values, how to determine the total amount of elements in all collections with LINQ?

public int AmountElements 
{
   get
   {
     return ??;
   }
}

Answer 1

要获取字典值中的元素总数：

myDict.Values.Sum(collection => collection.Count);

Answer 2

You can do as follows:

var count = myDict.SelectMany(d => d.Value).Count();

So you can write your AmountElements property as follows:

 public int AmountElements => myDict.SelectMany(d => d.Value).Count();