Appendix C. Data Marshaling

Appendix C. Data Marshaling

When calling between the runtime environment and existing COM interfaces, the CLR performs automatic data marshaling for CLR types into compatible COM types. Table C-1 describes the C# to COM default data type mapping.

Table C-1. C# type to COM type mapping

C# type

COM type

bool

VARIANT_BOOL

char

unsigned short

sbyte

Char

byte

Unsigned char

short

Short

ushort

Unsigned short

int

Int

uint

Unsigned int

long

Hyper

ulong

Unsigned hyper

float

Single

double

Double

decimal

DECIMAL

object

VARIANT

string

BSTR

System.DateTime

DATE[1]

System.Guid

GUID

System.Currency

CURRENCY

1-dimensional arrays

SAFEARRAY

Value types

Equivalently named struct

enum

Equivalently named enum

interface

Equivalently named interface

class

Equivalently named CoClass

[1] COM dates are less precise, causing comparison problems.

Table C-2. C# modifier/COM attribute mapping

C# modifier

COM attribute

<no modifier>

[in]

out

[out]

ref

[in, out]

<return value>

[out, retval]



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