DllImport and return parameters - pinvoke

Question

I am working on hardware testing. Our test framework is written in C# but we are using native dlls to talk to hardware.
Say we have a C++ method:
unsigned char someMethod(unsigned long * nativeStatus)
which in turns executes an embedded command and returns a status when command completes.
To use it we create a wrapper
[DllImport(#"native.dll", CharSet=CharSet.Ansi, CallingConvention=CallingConvention.Cdecl)]
internal static extern Byte someMethod(ref UInt32 managedStatus)
This works fine. But there is a scenario when someMethod call does not actually execute a command but just adds it to a sequence. Then the sequence can be executed by sending a special command say ExecuteSequence. As the sequence is being executed C++ code updates the nativeStatus by just copying the data into the memory referenced by the nativeStatus pointer. As the sequence completes ExecuteSequence method returns. At this time I am sure that all data (nativeStatus in this case) is updated. Will my managedStatus be correctly updated as well? I heard that in this case managedStatus and nativeStatus are not pointing to the same memory. Marshaler just returns a copy of nativeState after call completes. If not what is the solution? Do I need to use the unsave keyword and put my code creating and executing a sequence in the fixed{} block?
[DllImport(#"native.dll", CharSet=CharSet.Ansi, CallingConvention=CallingConvention.Cdecl)]
internal static unsave extern Byte someMethod(UInt32 * managedStatus)

Answer 1

So what you need is a variable location of which will not change over a timespan.
Yes, you can use fixed{} for that.
Alternatively, you can pin that variable:
private uint g_Pinnable = 0;
...
var gc = System.Runtime.InteropServices.GCHandle.Alloc(g_Pinnable, System.Runtime.InteropServices.GCHandleType.Pinned);
try
{
// Pass 'ref g_Pinnable' to API
// Then execute the sequence.
}
finally
{
gc.Free(); // Reference to g_Pinnable may be invalid after this point
}