Anonymous Delegates and generic Lists in C#

Question

Can you explain me code below :

private static List<Post> _Posts;
public static Post GetPost(Guid id)
{
    return _Posts.Find(delegate(Post p)
    {
        return p.Id == id;
    });
}

1. What is the point to find an object in a generic list by that way ? He can simply iterate the list.

2. How this delegated method called for each element of list ?

NOTE : if this has a common name, can you update my question's title ?

Thanks !

Answer 1

You're quite right he can iterate over the list, you can think of the code in your question as being conceptually the same as the following:

private static Post GetPost(Guid id)
{
    Post p = default(Post);

    foreach (Post post in _Posts)
    {
        if (post.Id == id)
        {
            p = post;
            break;
        }
    }

    return p;
}

It requires less code to write your snippet and importantly you are now saying what you want to be found and not exactly how to find it:

private static Post GetPost(Guid id)
{
    return _Posts.Find(delegate(Post p)
    {
        return p.Id == id;
    });
}

In C# 3.0 this can be shortened further using what is called a "lambda expression" to:

private static Post NewGetPost(Guid id)
{
    return _Posts.Find(p => p.Id == id);
}

Using the least amount of readable code to achieve the same goal makes both writers and readers of that code happier.

Answer 2

He is using an anonymous delegate. He could have used a lambda expression instead:

Posts.Find(p => p.Id == id)

Also, wrapping access to the list in a method achieves nothing in this case and exposes the elements of the list to external callers. This is bad practice.