Pretending .NET strings are value type

Question

In .NET, strings are immutable and are reference type variables. This often comes as a surprise to newer .NET developers who may mistake them for value type objects due to their behavior. However, other than the practice of using StringBuilder for long concatenation esp. in loops, is there any reason in practice that one needs to know this distinction?

What real-world scenarios are helped or avoided by understanding the value-reference distinction with regard to .NET strings vs. just pretending/misunderstanding them to be value types?

Answer 1

String is a special breed. They are reference type yet used by most coders as a value type. By making it immutable and using the intern pool, it optimizes memory usage which will be huge if it's a pure value type.

More readings here:
C# .NET String object is really by reference? on SO
String.Intern Method on MSDN
string (C# Reference) on MSDN

Update:
Please refer to abel's comment to this post. It corrected my misleading statement.

Answer 2

The only distinction that really matters for most code is the fact that null can be assigned to string variables.

Answer 3

An immutable class acts like a value type in all common situations, and you can do quite a lot of programming without caring much about the difference.

It's when you dig a little deeper and care about performance that you have real use for the distinction. For example to know that although passing a string as a parameter to a method acts as if a copy of the string is created, the copying doesn't actually take place. This might be a surprise for people used to languages where strings actually are value types (like VB6?), and passing a lot of strings as parameters would not be good for performance.