Type Support

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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