Share via


Type Support

[This documentation is for preview only, and is subject to change in later releases. Blank topics are included as placeholders.]

The following tables describe categories of types and the results of marshaling types from managed to unmanaged contexts.

Type Categories

The following table provides descriptions and clarifications for several of the types mentioned in the following sections.

Type

Description

Value types

Value types directly contain the data described and the memory for the value type is allocated from the stack.

Built-in value types

Int32, UInt32, Boolean, Single, and so on. For a complete list, see .NET Framework Class Library Overview.

User-defined value types

Derived from System.ValueType. In C#, a user-defined value type is defined using the struct keyword.

Enumerations

Enumerations are also value types. The underlying type of an enumeration in the .NET Framework is Int32. However, you can explicitly define an enumeration to have another underlying type. The supported underlying types are any integral base types except Char.

Reference type

Reference types store a reference to an object's memory that was allocated on the heap. These can be built-in classes, user-defined classes, arrays, boxed value types, delegates, and so forth.

Managed to Unmanaged Types

The following table describes the result of marshaling managed types to unmanaged types.

Managed type

Unmanaged type

Value type (including greater than 32 bits)

Unmodified.

Reference to value type

Pointer to the value type.

64-bit integer

Pointer to array of value types.

Floating-point number

Floating-point number.

Array of value types

Pointer to array of value types.

Enum

Underlying value type of the enumeration.

ANSI string

Only supported if passed as an array of bytes.

String

Pointer to a null-terminated array of Unicode (wchar_t) characters. Unmanaged code should not modify the array.

Reference type

Pointer to the underlying data fields of the object. Reference types are always marshaled sequentially. You can marshal only objects that contain value-type members.

Reference to reference type

Not supported.

Array of reference types

Not supported.

Delegate

Function pointer

StringBuilder

Pointer to a null-terminated array of Unicode (wchart_t) characters. Unmanaged code can modify the array.

C# and Visual Basic Marshaling Results

The following table lists C# and Visual Basic types used by the marshaler for managed types, with Windows CE as the operating system hosting the unmanaged code. This list is not comprehensive.

Managed code

C# types

Managed code

Visual Basic types

Unmanaged code

ByVal

Unmanaged code

ByRef

bool

Boolean

BYTE

BYTE *

int

Integer

INT32

INT32 *

short

Short

SHORT

SHORT *

long

Long

LONG

INT64 *

char

Char

WCHAR

WCHAR *

float

Single

FLOAT

FLOAT *

double

Double

DOUBLE

DOUBLE *

string

String

WCHAR *

Not supported

StringBuilder

StringBuilder

WCHAR *

Not supported

DateTime

DateTime

DATE

DATE *

int[]

Integer()

INT32 *, INT32[]

Not supported

Variant Type Support

The following table lists the types from the VARENUM enumeration supported by the IDispatch marshaler for marshaling from managed to unmanaged code. In all cases, the types are supported both for parameters and return types. The unsupported types include those not applicable to variant types.

Supported types

Unsupported types

VT_I2

VT_I4

VT_CY

VT_DATE

VT_BSTR

VT_DISPATCH

VT_ERROR

VT_BOOL

VT_VARIANT

VT_UNKNOWN

VT_DECIMAL

VT_I1

VT_UI1

VT_UI2

VT_UI4

VT_INT

VT_UINT

VT_ARRAY

VT_R8

VT_R4

VT_CF

VT_CLSID

VT_EMPTY

VT_NULL

VT_I8

VT_UI8

VT_USERDEFINED

VT_RECORD

VT_SAFEARRAY (use VT_ARRAY)

VT_PTR

VT_HRESULT

VT_VOID

VT_CARRAY

VT_LPSTR (use VT_BSTR)

VT_LPWSTR (use VT_BSTR)

VT_FILETIME

VT_BLOB

VT_STREAM

VT_STORAGE

VT_STREAMED_OBJECT

VT_STORED_OBJECT

VT_BLOB_OBJECT

VT_VECTOR

See Also

Other Resources

Marshaling Support in the .NET Compact Framework