Question

Is there any need to set a string member variable of a class to “”? Will it be null unless you do this?

Answer 1

The reason a string will be null is because a string is a reference type and the default value for all reference types is null (i.e. no reference).

The best reference is the Default Values Table (remember all reference types are set to null by default) but some examples below give a decent idea:

string a = default(string); // null
String b = default(String); // null
int c = default(int); // 0
int? d = default(int?); // null
Object e = default(object); // null
double f = default(double); // 0.0

// an instance of someStruct with fields set to default(theirType)
someStruct g = default(someStruct); 

A string kind of seems to be a value type because it seems so primitive. Additionally it is immutable meaning that you can never modify a string, instead you just set string symbols to point to new string “values” (which are themselves references), giving the impression that string is a value type.

For example:

 string a = "boo"; 
 /* Mem contains reference to "boo" and symbol 'a' => reference("boo") */

 a = "gah";
 /* Mem contains references to "boo" and "gah". symbol 'a' -> reference("gah") */

For more info on strings see this great article.

And don’t forget the Default Values Table.