Using the MarshalAsAttribute Attribute

You can use the MarshalAsAttribute attribute to customize marshaling behavior. For example, you can perform the following tasks:

Marshal arrays and strings in a structure.
Provide needed flexibility to support common COM interop scenarios.
Provide consistency in marshaling types through the platform invoke and vtable marshaler as compared to the IDispatch marshaler.

The following table describes marshaling support for the values from the UnmanagedType enumeration.

Unmanaged Type	Types valid on	Supported in structures
BStr, TBStr	String
LPWStr, LPStr, LPTStr	String	Yes
IUnknown	Object	Yes
IDispatch	Object	Yes
ByValTStr	String (in structures only)	Yes
ByValArray	Any array	Yes
SafeArray	Any array	Yes
VBByRefStr	String
Bool	Boolean, integer types
I1, I2, I4	Integer types of appropriate length
U1, U2, U4	Unsigned integer types of appropriate length
I8	N/A
U8	N/A
R4	4-byte real numbers
R8	8-byte real numbers
Struct	Object
Interface	Object
SysInt, SysUInt	Integer types of appropriate sign and length
AnsiBStr	N/A
VariantBool	Boolean
FunctionPtr	N/A
AsAny	N/A
LPArray	N/A
LPStruct	N/A
Error	4 byte integers
Currency	Decimal

See Also