System.Runtime.InteropServices.Marshal (class)

Memory allocation and releasing

The Marshal class provides two (direct) memory allocation methods:

AllocCoTaskMem (The «COM task memory allocator»)
AllocHGlobal (which allocates unmanaged memory and exposes the WinAPI function LocalAlloc from kernel32.dll)
FreeHGlobal (which frees memory that was allocated with AllocHGlobal)

PtrToXXX

The PtrToXXX methods allocate managed memory and fills it with the data that a (unmaanged) pointer points at:

PtrToStringAnsi
PtrToStringAuto
PtrToStringBSTR
PtrToStringUni
PtrToStringUTF8
PtrToStructure (Compare with StructureToPtr)

StringToXXX

The StringToXXX allocate different «kinds» of unmanaged memory and copies the managed string data to that newly allocated memory:

StringToBSTR
StringToCoTaskMemAnsi
StringToCoTaskMemAuto
StringToCoTaskMemUni
StringToCoTaskMemUTF8
StringToHGlobalAnsi
StringToHGlobalAuto
StringToHGlobalUni

ReadXXX / WriteXXX

The ReadXXX and WriteXXXX methods read 1, 2, 4 or 8 bytes and return a corresponding System.Byte short (= System.Int16?), System.Int32 etc:

ReadByte / WriteByte
ReadInt16 / WriteInt16
ReadInt32 / WriteByte32
ReadInt64 / WriteByte64
ReadIntPtr / WriteIntPtr64

SizeOf

SizeOf comes in four overloads. This method returns the size of the (unmanaged) bytes that a managed byte in fact requires to store its data:

SizeOf(Object)
SizeOf(Type)
SizeOf<T>()
SizeOf<T>(T)

GetActiveObject

The GetActiveObject(progid) method tries to locate an object with the given progid in the Running Object Table and returns the corresponding COM Object if it was found. If such an object is not found, a System.Runtime.InteropServices.COMException is thrown.

The following PowerShell example makes sure that the script does not start an additional Excel instance.

$progId = 'Excel.Application';

try {
   $comObj = [System.Runtime.InteropServices.Marshal]::GetActiveObject($progId);
   write-output "$progId was found in the RunningObject Table, activating it";

 #
 #  https://stackoverflow.com/a/36717974/180275
 #
   $comObj.windowState = -4140 # xlMinimized
   $comObj.windowState = -4137 # xlMaximized
}
catch [System.Runtime.InteropServices.COMException] {

   write-output "$progId was not found in the Running Object Table, starting it.";

   $comObj = new-object -comObject $progId
   $comObj.visible = $true
}

Github repository .NET-API, path: /System/Runtime/InteropServices/Marshal/GetActiveObject/check-if-object-exists.ps1

The VBA equivalent of GetActiveObject() seems to be getObject()

In .NET Core , there is no GetActiveObject() method anymore, so this functionality must be accessed with P/Invoke.

COM related methods

COM related COM methods include:

AddRef and its counterpart Release
GetComInterfaceForObject (returns IntPtr)
GetIUnknownForObject (returns IntPtr)
GetIDispatchForObject (returns IntPtr)
QueryInterface
GetEndComSlot
IsComObject
GetObjectForIUnknown

Other methods

`AreComObjectsAvailableForCleanup()`
`BindToMoniker()`
`ChangeWrapperHandleStrength()`
`CleanupUnusedObjectsInCurrentContext()`
`Copy()`
`CreateAggregatedObject()`
`CreateWrapperOfType()`
`DestroyStructure()`
`FinalReleaseComObject()`
`FreeBSTR()`
`FreeCoTaskMem()`
`GenerateGuidForType()`
`GenerateProgIdForType()`
`GetComObjectData()`
`GetDelegateForFunctionPointer()` and `GetFunctionPointerForDelegate()`	converts an unmanaged function pointer to a `System.Delegate` and vice versa
`GetExceptionCode()`
`GetExceptionForHR()`
`GetExceptionPointers()`
`GetHINSTANCE()`
`GetHRForException()`
`GetHRForLastWin32Error()`
`GetLastPInvokeError()`
`GetLastSystemError()`
`GetLastWin32Error()`
`GetNativeVariantForObject()`
`GetObjectForNativeVariant()`
`GetObjectsForNativeVariants()`
`GetStartComSlot()`
`GetTypedObjectForIUnknown()`
`GetTypeFromCLSID()`	Compare with the method with the same name in `System.Type`
`GetTypeInfoName()`
`GetUniqueObjectForIUnknown()`
`InitHandle()`
`IsTypeVisibleFromCom()`
`OffsetOf()`
`Prelink()`
`PrelinkAll()`
`ReAllocCoTaskMem()`
`ReAllocHGlobal()`
`ReleaseComObject()`
`SecureStringToBSTR()`
`SecureStringToCoTaskMemAnsi()`
`SecureStringToCoTaskMemUnicode()`
`SecureStringToGlobalAllocAnsi()`
`SecureStringToGlobalAllocUnicode()`
`SetComObjectData()`
`SetLastPInvokeError()`
`SetLastSystemError()`
`StructureToPtr()`
`ThrowExceptionForHR()`
`UnsafeAddrOfPinnedArrayElement()`
`ZeroFreeBSTR()`
`ZeroFreeCoTaskMemAnsi()`
`ZeroFreeCoTaskMemUnicode()`
`ZeroFreeCoTaskMemUTF8()`
`ZeroFreeGlobalAllocAnsi()`
`ZeroFreeGlobalAllocUnicode()`