Structs

A struct is similar to a class, with the following key differences:

• A struct is a value type, whereas a class is a reference type.

• A struct does not support inheritance (other than implicitly deriving from object, or more precisely, System.ValueType).

A struct can have all the members a class can, except a parameterless constructor, a finalizer, and virtual members.

A struct is used instead of a class when value-type semantics are desirable. Good examples are numeric types, where it is more natural for assignment to copy a value rather than a reference. Because a struct is a value type, each instance does not require instantiation of an object on the heap; this can result in a useful saving when creating many instances of a type. For instance, creating an array of value types requires only a single heap allocation.

Struct Construction Semantics

The construction semantics of a struct are as follows:

• A parameterless constructor that you can’t override implicitly exists. This performs a bitwise-zeroing of its fields.

• When you define a struct constructor (with parameters), you must explicitly assign every field.

• You can’t have field initializers in a struct.