Question

Say you have a group of objects you’re creating to handle some XML parsing and all of them take the exact same object, XElement … as such

public class User
{
    public User(XElement xmlElement)
    {
          Id = xmlElement.GetElementValue("UserId"); 
    }

    public string Id { get; set; }
}

What I would like to do is a method kinda like this ..

public static T ToParsedObject<T>(this XElement xmlElement) where T : new()
{
    return new T(xmlElement);
}

I don’t think it’s possible to do a static (extension method) like this, but I would like to make this a single method I can re-use. I’m tired of writing ones like …

public static User ToUser(this XElement xmlElement)
{
    return new User(xmlElement);
}

Any ideas or guidance?

Answer 1

You can pull this off with reflection:

public static class XElementExtensions
{
    public static T To<T>(this XElement el)
    {
        //var ctor = typeof(T).GetConstructor(new[] { typeof(XElement) });
        //if (ctor == null) /* do something */

        return (T)Activator.CreateInstance(typeof(T), new[] { el });
    }
}

You don’t need the constructor check in there, but it would be necessary if you wanted to take special action, like returning default(T).

You would use this method like this:

User u = xmlElement.To<User>();

I do wonder, though, what the benefit of this is over simply calling the constructor on your objects:

User u = new User(xmlElement);

Heck, it’s one less character! 🙂