TimL on C#.NET

While doing a review of a colleague's code, I happened to come across a statement similar to the one below.

string myString = someVariable + "";

 

I immediately flagged this is a potential problem, saying that this would throw an exception if someVariable is null. And, realizing that he was just trying to ensure that the myString is not null, I suggested doing something like the following instead.

string myString = (someVariable != null) ? someVariable : "";

 

After talking with him in the hall after the code review, he assured me that his code worked the original way. So, I naturally pulled up Visual Studio and gave it a try, and he was right! [ This just goes to show that no matter how much one thinks he or she knows about a programming language, there is always room to learn more! ]

I looked up the String class in MSDN, and expected to see an overloaded + plus operator (op_Addition), but found no such thing. So, I turned to the C# spec. Sure enough, Ecma-334 section 14.7.4 states the following:

"The binary + operator performs string concatenation when on or both operands are of type string. If an operand of string concatenation is null, an empty string is subsituted. Otherwise, any non-string operand is converted to its string representation by invoking the virtual ToString method inherited from type object. If ToString returns null, an empty string is substituted."