Count property vs Count() method?

by

Decompiling the source for the Count() extension method reveals that it tests whether the object is an ICollection (generic or otherwise) and if so simply returns the underlying Count property:

So, if your code accesses Count instead of calling Count(), you can bypass the type checking – a theoretical performance benefit but I doubt it would be a noticeable one!

// System.Linq.Enumerable
public static int Count<TSource>(this IEnumerable<TSource> source)
{
    checked
    {
        if (source == null)
        {
            throw Error.ArgumentNull("source");
        }
        ICollection<TSource> collection = source as ICollection<TSource>;
        if (collection != null)
        {
            return collection.Count;
        }
        ICollection collection2 = source as ICollection;
        if (collection2 != null)
        {
            return collection2.Count;
        }
        int num = 0;
        using (IEnumerator<TSource> enumerator = source.GetEnumerator())
        {
            while (enumerator.MoveNext())
            {
                num++;
            }
        }
        return num;
    }
}

More Related Contents:

  1. How to Quickly Remove Items From a List
  2. Compare Two Lists Via One Property Using LINQ
  3. Return max repeated item in list
  4. Can’t use Count() in C#
  5. Convert List to List
  6. Flatten List in LINQ
  7. Using LINQ to remove elements from a List
  8. Quickest way to compare two generic lists for differences
  9. How can I get every nth item from a List?
  10. Combination of List
  11. How to check if IEnumerable is null or empty?
  12. How to easily initialize a list of Tuples?
  13. Linq select objects in list where exists IN (A,B,C)
  14. How to get the closest number from a List with LINQ?
  15. Find the most occurring number in a List
  16. Does Distinct() method keep original ordering of sequence intact?
  17. how to check if object already exists in a list
  18. Conversion from List to array T[]
  19. LINQ to find series of consecutive numbers
  20. C#: How to convert a list of objects to a list of a single property of that object?
  21. Easiest way to Rotate a List in c#
  22. LINQ .Any VS .Exists – What’s the difference?
  23. How to find List has duplicate values in List [duplicate]
  24. How to count the number of elements that match a condition with LINQ
  25. C# List – Removing items while looping / iterating [duplicate]
  26. List.Except is not working
  27. Remove duplicate items from list in C#, according to one of their properties
  28. Sort one list by another
  29. Sorting a List
  30. What is the best way to check two List lists for equality in C#

Leave a Comment