ErrorWrapper Class

Updated: February 2010

Wraps objects the marshaler should marshal as a VT_ERROR.

Namespace:  System.Runtime.InteropServices
Assembly:  mscorlib (in mscorlib.dll)

[SerializableAttribute]
[ComVisibleAttribute(true)]
public sealed class ErrorWrapper

By default, Object type arguments are marshaled as a VARIANT type, where the object type determines the VARTYPE value of the VARIANT.

The ErrorWrapper type must to be passed as an Object type to be marshaled as a VARIANT of type VT_ERROR, otherwise the ErrorWrapper type is marshaled as an integer.

The following table illustrates marshaling in a managed call to a native function, using platform invoke.

Managed signature parameter

pArr value

Marshaled as

ErrorWrapper[] pArr

ErrorWrapper[10] of ErrorWrapper(77)

Int[10]

Object[] pArr

ErrorWrapper[10] of ErrorWrapper(77)

VARIANT[10] of VT_ERROR

Object[] pArr

Object[10] of ErrorWrapper(77)

VARIANT[10] of VT_ERROR

The following table illustrates marshaling data in a managed call to a native function, using COM runtime callable wrappers (RCW).

Managed signature parameter

pArr value

Marshaled as

ErrorWrapper[] pArr

ErrorWrapper[10] of ErrorWrapper(77)

Int[10]

Object[] pArr

ErrorWrapper[10] of ErrorWrapper(77)

SafeArrayTypeMismatch exception

Object[] pArr

Object[10] of ErrorWrapper(77)

SAFEARRAY(VARIANT)

Note that ErrorWrapper objects are not marshaled as type VT_ERROR after they are passed back from COM. A single value is marshaled back from COM as type VT_I4, while arrays are marshaled back from COM as type VT_UI4.

For more information on VT_ERROR, please see the existing documentation for VARENUM::VT_ERROR in the MSDN library.

The following code example first demonstrates a lone Int32 object marshaled back from COM as an Int32 object. It then demonstrates an Int32 array marshaled back from COM as a UInt32 array.

// Scenario 1:
// Pass a single value.
Int32 x = 3;
Object o = new ErrorWrapper(x);
// Pass 'o' to COM.
// On the return trip, 'o' has been unwrapped and is still an Int32 object.
Int32 y = (Int32)o;
Scenario 2:
// Pass an array of values.
Int32[] arr = new Int32[3];
Object o = new ErrorWrapper(arr);
// Pass 'o' to COM.
// On the return trip, 'o' has been unwrapped and is now a UInt32[] array.
UInt32[ ] arr2 = (UInt32[])o;

System.Object
  System.Runtime.InteropServices.ErrorWrapper

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0

Date

History

Reason

February 2010

Clarified the marshaling behavior.

Content bug fix.

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