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.

If its any help, you could use the 'as' operator which is similar to the cast but returns null instead of an exception on any conversion failure.

string str3 = obj as string;