How does appending to a null string work in C#?

Question

I was surprised to see an example of a string being initialised to null and then having something appended to it in a production environment. It just smelt wrong.

I was

Answer 1

The relevant citation should be ECMA-334 §14.7.4:

String concatenation:

string operator +(string x, string y);
string operator +(string x, object y);
string operator +(object x, string y);  

The binary + operator performs string concatenation when one or both operands are of type string. If an operand of string concatenation is null, an empty string is substituted. 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.