Using 'this' statement in static method pros/cons in C#

Hello,

I'm using a static method to get information from COM object like;

public static string GetBodyName(this IScrBody obj) { //some code}

With that i'm able use it like;

var myBodyName = Body.GetBodyName()

in before i'm using like that;

public static string GetBodyName(IScrBody obj) { //some code}

and i'm trying to return a value

var myBodyName = GetBodyName(obj)

Now i've search on net but didn't find like i expected.

Now i'd like to know are there any pros/cons of using this statement.

I really need expert's advice.

Any help would be great!
Thank you.