Casting to string versus calling ToString

• (string)obj casts obj into a string. obj must already be a string for this to succeed.
• obj.ToString() gets a string representation of obj by calling the ToString() method. Which is obj itself when obj is a string. This (should) never throw(s) an exception (unless obj happens to be null, obviously).

So in your specific case, both are equivalent.

Note that string is a reference type (as opposed to a value type). As such, it inherits from object and no boxing ever occurs.