Type Classification in the CLR

The CLR groups types into two different categories: reference types, and value types. Reference types are allocated off of the managed heap. They include all object references, interfaces, and managed pointer types. Reference types have alias semantics, meaning that copying the reference results in an alias. A change to the alias is also reflected in the original reference.

 

In contrast, value types have value semantics for assignment and copying. Assigning or copying a value type results in two distinct entities, and a change in one does not affect the other. Value types include scalar values, and enumerations. Value types incur a much smaller performance and resource penalty, as they are allocated on the thread's stack (as opposed to the managed heap). In Delphi for Microsoftâ .NET, records are value types.

 

Delphi for .NET supports packed records, however the semantics of this keyword are changed slightly. In Delphi for .NET, the packed keyword means the JIT compiler cannot move, reorder, or add padding between fields of a record. The packed keyword effectively disables the JIT compiler's ability to optimize the layout of a record type. The ability to disable such optimization can be important when creating value types that will be used to interoperate with unmanaged code.

 

Primitive Type Mapping

 

Delphi Type	.NET Framework Type
ShortInt	System.SByte
Byte	System.Byte
SmallInt	System.Int16
Word	System.UInt16
Integer	System.Int32
Cardinal/LongWord	System.UInt32
Int64	System.Int64
UInt64	System.UInt64
Char/WideChar	System.Char
Single	System.Single
Double/Extended	System.Double
Boolean	System.Boolean
WideString/string	System.String

 

Notes:

• The extended type has been remapped to System.Double, which is an 8-byte floating-point type.
• The Char type is now two bytes
• The string type is now a wide string.
• Two new types, NativeInt, and NativeUInt are not CLS compliant.