obj.ToString(); vs obj + "";

[Ray Proffitt]

Hi.

obj.ToString();

or

obj + "";

Which is more efficient and why?

 

[Marc Gravell]

Which is more efficient and why?

By a *very* small margin, the first. The second compiles to
string.Concat(obj) [note that the + "" is optimised away]. This is an
additional method call (which is possibly inlined), but which does an
additional null check (returning "" if obj is null) before calling the
same obj.ToString().

The difference will be stupidly small, and is unlikely to *ever* show
on any performance trace - so go with whichever is simplest to read.
For me, the first wins this. Note that they behave differently for obj
= null, though.

Marc

 

[Göran Andersson]

Hi.

obj.ToString();

or

obj + "";

Which is more efficient and why?

The first is slightly more efficient.

Also, it's better from a maintainability perspective. The first code
does exactly what it says, nothing more and nothing less. The second
code describes a nonsense-operation that only has the purpose of causing
an implicit conversion.

 

[Hilton]

Ray,

No-one has mentioned the case of obj==null. Makes the two statements quite
different.

Hilton

 

[Marc Gravell]

No-one has mentioned the case of obj==null.

Except for: "but which does an additional null check (returning "" if
obj is null) "
and "Note that they behave differently for obj = null, though."

Marc

 

[Ray Proffitt]

Thanks folks... It's ToString() from now on; always prefered it
anyway.

 

[Arne Vajhøj]

obj.ToString();

or

obj + "";

Which is more efficient and why?

The first, but it does not matter.

What is important is what code clearly expresses
the intent of the code.

And in that aspect the first wins huge.

Arne

 

[Alex Meleta]

Convert.ToString(obj). Clear. Safe.

Otherwise, if you good in checking of nulls use your first one. It's much
obvious.

Regards, Alex Meleta
mailto:[email protected]; blog:devkids.blogspot.com