Anonymous types

Question

Hello,

My first try to use anonymous types(test):

    private void button4_Click(object sender, EventArgs e)
    {
        test(new { a = "asd" });
    }

    private void test(string a)
    {
    }

I get an error "cannot convert from 'AnonymousType#1' to 'string' "

Also I'd like to know how to pass an anonymous type if the parameter is a string[]

    private void test(string[] a)
    {
    }

Thanks in advance!

Answer 1

There is no clean way to pass an anonymous type between methods; you're not meant to do it. Create a real type instead.

If you really really want to do this, you can use a helper method to fake it awkwardly by creating another "template" of that type to cast to later; see this and many similar articles.

EDIT: On closer examination, you don't appear to understand what an anonymous type actually is, so I suggest you take the other answers.

Answer 2

Something about your design is faulty. If your test function accepts only strings, then you can never pass an anonymous type to it, just as you can't pass an int, object, or any other non-string type.

Answer 3

a is a string property on your anonymous type

private void button4_Click(object sender, EventArgs e)
{
    test((new { a = "asd" }).a);
}

private void test(string a)
{
}

Edit: Anonymous types do not derive from anything other than object so you cannot create a method that expects an anonymous type parameter.

Edit 2: when you create an anonymous type the compiler create an entirely new type based on the properties you set and the order in which they appear. You cannot create an anonymous type and use it in place of any other type (other than object). The most common scenario I've used them in is for binding when you need to flatten your object graph.

warning, I am horrible at coming up with good example scenarios and this is all from memory! for example if I had a list of Person objects that had a name property and an address property that contained the street address and needed to bind to a list box

var people = new List<Person>()
listbox.TextMember = "Text";
listbox.ValueMember = "Value"
listbox.DataSource = from p in people 
select new { Text = p.Name, Value = p.Address.StreetAddress };

Answer 4

This is bad, but it works ...

namespace AnonType
{
    class Program
    {
        static void Main(string[] args)
        {
            var foo = new { a = "123", b = "abc" };

            Anon(foo);
            Console.ReadLine();
        }

        public static void Anon(object o)
        {
            Console.WriteLine(o);
        }
    }
}