MarshalAs Attribute

MarshalAs Attribute

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Class

System.Runtime.InteropServices.MarshalAsAttribute

Applies to

Field, Parameter, ReturnValue

Description

Defines the correct type conversion between managed and unmanaged code. Unmanaged types are defined by the UnmanagedType enumeration, which is shown in the following table:

UnmanagedType	Value	Description
AnsiBStr	35	An ANSI BSTR (a character string whose first byte indicates the string length).
AsAny	40	Dynamic type determination at runtime.
Bool	2	4-byte Boolean ( True <> 0, False = 0).
BStr	19	A Unicode BSTR (a character string whose first 2 bytes indicates the string length).
ByValArray	30	An array passed by value. An array that is a field in a structure must have this attribute. The SixeConst field must be set to the number of array elements, and the ArraySubType field can optionally be set to the unmanaged data type of the array.
ByValTStr	23	An inline fixed-length character array within a structure. The character type is determined by the CharSet argument of the containing structure's <StructLayout> attribute.
Currency	15	A COM Currency data type. Used on the VB.NET and .NET Decimal data type.
CustomMarshaler	44	A custom marshaler class. The class is defined by the MarshalType or MarshelTypeRef field. Additional information can be passed to the custom marshaler by the MarshalCookie field.
Error	45	An HRESULT . The native .NET type should be a 4-byte signed or unsigned integer.
FunctionPtr	38	A function pointer.
I1	3	A 1-byte signed integer.
I2	5	A 2-byte signed integer.
I4	7	A 4-byte signed integer.
I8	9	An 8-byte signed integer.
IDispatch	26	A COM IDispatch pointer.
Interface	28	A COM interface pointer.
IUnknown	25	A COM IUnknown pointer.
LPArray	42	A C-style array. Its length is indicated by the SizeConst and SizeParamIndex fields. Optionally, the ArraySubType field can indicate the unmanaged type of string elements within the array.
LPStr	20	An ANSI (single-byte) character string.
LPStruct	43	A pointer to a structure.
LPTStr	32	A platform-dependent character string (ANSI on WIndows 9x, Unicode on WIndows NT/2000/XP). LPTStr is supported only for platform invoke, and not for COM interop.
LPWStr	21	A Unicode (double-byte) character string.
R4	11	A 4-byte floating point number.
R8	12	An 8-byte floating point number.
SafeArray	29	A SafeArray (a self-describing array that includes information on its type, dimension, and bounds).
Struct	27	A C-style structure used to marshal .NET formatted classes and value types.
SysInt	31	A platform-dependent integer (4 bytes on 32-bit Windows, 8 bytes on 64-bit Windows).
SysUInt	32	The hardware's natural sized unsigned integer.
TBStr	36	A length-prefixed, platform-dependent character string (ANSI in Windows 9x, Unicode on Windows NT/2000/XP).
U1	4	A 1-byte unsigned integer.
U2	6	A 2-byte unsigned integer.
U4	8	A 4-byte unsigned integer.
U8	10	An 8-byte unsigned integer.
VariantBool	37	A 2-byte OLE-defined Boolean value ( True = -1, False = 0).
VBByRefStr	34	Allows Visual Basic to change a string in unmanaged code and reflect the changed skin in managed code.

Constructor

 New(   unmanagedType   ) 

unmanagedType (Short or UnmanagedType enumeration)

Indicates the COM (unmanaged) data type to which the data is to be converted. unmanagedType can either be a constant of the UnmanagedType enumeration or its corresponding Short value, as shown in the previous table.

Properties

Value ( UnmanagedType enumeration)

The COM (unmanaged) data type that the .NET (managed) data is to be marshaled as.

Fields

ArraySubType ( UnmanagedType enumeration)

The subtype of an array of type ByValArray or LPArray . It is used when an array contains strings so that the runtime knows how to marshal a string array to COM.

MarshalCookie (String)

An undefined field that can be used to pass user -defined data to a custom marshaler. The value of the MarshalCookie field as passed to the custom marshaler's GetInstance method.

MarshalType (String)

The fully qualified name of a custom marshaler. It is required if the Value property is CustomMarshaler .

MarshalTypeRef (Type)

Implements the MarshalType value as a Type, rather than a string.

SafeArraySubType ( VarEnum enumeration)

The data type of a SafeArray. Possible values are the members of the VarEnum enumeration, which is shown in the following table:

Constant	Description
VT_ARRAY	A SAFEARRAY pointer
VT_BLOB	A length-prefixed collection of bytes
VT_BLOB_OBJECT	A VT_BLOB containing an object
VT_BOOL	A Boolean value
VT_BSTR	A string of type BSTR
VT_BYREF	A value passed by reference
VT_CARRAY	A C-style array
VT_CF	Clipboard format
VT_CLSID	A class identifier (CLSID)
VT_CY	A currency value
VT_DATE	A date value
VT_DECIMAL	A decimal value
VT_DISPATCH	An IDispatch pointer
VT_EMPTY	A value was not specified
VT_ERROR	An SCODE
VT_FILETIME	A FILETIME value
VT_HRESULT	An HRESULT
VT_I1	A char value
VT_I2	A short (two-byte) integer
VT_I4	A long (4-byte) integer
VT_I8	A 64-bit integer
VT_INT	An integer value
VT_LPSTR	A null- terminated string
VT_LPWSTR	A null-terminated Unicode string
VT_NULL	A null reference ( Nothing )
VT_PTR	A pointer
VT_R4	A floating-point value
VT_R8	A double value
VT_RECORD	A user-defined type
VT_SAFEARRAY	A SAFEARRAY
VT_STORAGE	A named storage
VT_STORED_OBJECT	Storage containing an object
VT_STREAM	A named stream
VT_STREAMED_OBJECT	A Stream containing an object
VT_UI1	An unsigned byte
VT_UI2	An unsigned (2-byte) short
VT_UI4	An unsigned (4-byte) long
VT_UI8	A 64-bit unsigned integer
VT_UINT	An unsigned integer
VT_UNKNOWN	An IUnknown pointer
VT_USERDEFINED	A user-defined type
VT_VARIANT	A VARIANT far pointer
VT_VECTOR	A simple counted array
VT_VOID	A C-style void

SafeArrayUserDefinedSubType (Type object)

The user-defined type of the SAFEARRAY . This field is used only if the value of the SafeArraySubType field is VT_UNKNOWN , VT_DISPATCH , or VT_RECORD .

SizeConst (Integer)

The number of elements in a fixed-length array

SizeParamIndex (Short)

Indicates which zero-based parameter contains a count of array elements