C# - (this T obj) - feature name

Question

Hello,

I have a function like this. Works well, but why?

public static string ToXML<T>(this T obj)

I call it without parameter! I think the reason is this
What is this mechanism called?
How can I see if this exists, perhaps via IntelliSense?

var xmlBody = message.ToXML();
Console.WriteLine("xml:" + xmlBody);

AtnSWO

using System;
using System.Xml.Serialization;
using System.Collections.Generic;

using myTest;

namespace myTest
{
    public class Program
    {
        public static void Main()
        {
            var invoice = new Invoice(Guid.NewGuid(), 123) { Name = "Jürgen Bauer"};
            var body = new Body();
            body.AddInvoice(invoice);

            var message = new Message() { Body = body };

            var xmlBody = message.ToXML();
            Console.WriteLine("xml:" + xmlBody);
        }
    }

    [XmlType("invoice")]
    public class Invoice
    {
        public Invoice()
        {
            this.EventId = Guid.NewGuid();
        }

        public Invoice(Guid eventId, System.Int64 number)
        {
            this.EventId = eventId;
            this.Number = number;
        }

        [XmlAttribute("eventid")]
        public System.Guid EventId
        {
            get;
            set;
        }

        [XmlAttribute("number")]
        public System.Int64 Number
        {
            get;
            set;
        }

        [XmlElement("name")]
        public string Name
        {
            get;
            set;
        }

        // Other Code //
    }

    public static class XMLHelper
    {
        public static string ToXML<T>(this T obj)
        {
            using (var stringwriter = new System.IO.StringWriter())
            {
                var serializer = new System.Xml.Serialization.XmlSerializer(typeof(T));
                serializer.Serialize(stringwriter, obj);
                return stringwriter.ToString();
            }
        }
    }

    [XmlType("message")]
    public class Message
    {
        [XmlElement("body")]
        public Body Body {get; set;}
    }


    public class Body
    {
        public Body()
        {
            this.SaveInvoices = new List<Invoice>();
        }
        [XmlArray("saveInvoice")]
        public List<Invoice> SaveInvoices {get; private set;}

        public void AddInvoice (Invoice invoice)
        {
            this.SaveInvoices.Add(invoice);
        }
    }
}

Answer 1

Hi @Markus Freitag

Which class are you referring too, a specific third party assembly? Two options and may depend on if a .pdb file exists, one using Visual Studio, one a paid for tool (there may be similar tools to look at, I favor dopeek).

Both ideas use the same .DLL files. Object browser provides signatures while dotpeek (paid for tool) provides decompiling.

Visual Studio Object browser

Jet brains dotpeek

Another thought is to set

Tools -> Options -> Debugging -> Uncheck "Just my Code"

Then place your mouse cursor on something and right click to goto definition (I'm guessing as I have a extension which overrides goto definition).

Answer 2

1) This is called Extension Methods.

2) You have to compile it once first at least for older version of Visual Studios.