Questions about Structs

There are a couple different answers to this question, and it is a bit subjective, but some reasons I can think of are:

• structs are value-type, classes are reference type. If you're using 16 bytes for total storage, it's probably not worth it to create memory references (4 to 8 bytes) for each one.
• When you have really small objects, they can often be pushed onto the IL stack, instead of references to the objects. This can really speed up some code, as you're eliminating a memory dereference on the callee side.
• There is a bit of extra "fluff" associated with classes in IL, and if your data structure is very small, none of this fluff would be used anyway, so it's just extra junk you don't need.

The most important difference between a struct and a class, though, is that structs are value type and classes are reference type.

By "efficient", they're probably talking about the amount of memory it takes to represent the class or struct.

On the 32-bit platform, allocating an object requires a minimum of 16 bytes. On a 64-bit platform, the minimum object size is 24 bytes. So, if you're looking at it purely from the amount of memory used, a struct that contains less than 16 bytes of data will be "better" than the corresponding class.

But the amount of memory used is not the whole story. Value types (structs) are fundamentally different than reference types (classes). Structs can be inconvenient to work with, and can actually cause performance problems if you're not careful.

The real answer, of course, is to use whichever works best in your situation. In most cases, you'll be much better off using classes.

Check this link, I found it on one of the answers in SO today: .NET Type Internals. You can also try searching SO and Googling for "reference types vs value types" for differences between structs and classes.

What restricts a struct from acting like a class?

There are many differences. You cannot inherit from a struct, for example.

You can't have virtual methods, so you cannot use a struct to implement an interface. Instance methods in structs can access struct's private fields, but apart from that they behave a lot like auxilirary "helper" functions (for immutable structs, they sometimes don't even need to access private data). So I find them to be not as near as "valuable" as class methods.