VB.NET Language in a Nutshell, Second Edition

Name

MarshalAs Attribute

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.