LayoutKind.Expl icit breaks service install

[Dave]

I have a structure declared as:

[StructLayout(La youtKind.Explic it, Size=6)]
private struct StandardFrame
{
[FieldOffset(0)] public byte [] frame;
[FieldOffset(0)] public UInt32 integrityCheck;
[FieldOffset(2)] public UInt32 sequenceNo;
[FieldOffset(4)] public UInt32 dataLength;

}

This is part of a Windows Service C# app. I've added an installer and
setup project but the install fails with "Unable to get installer types
in the <name of executable> --> one or more of the types in the
assembly unable to load."

I've narrowed the problem down to this struct. If I make the struct
LayoutKind.Sequ ential and remove the FieldOffset values the service
installs no problem. Obviously this is not what I want, the struct is
to be used as a union. This has really got me stumped, I can work
around it but I would prefer to use this approach.

Any clues gratefully accepted.

[Chris Dunaway]

I have code in VB.Net to install a service using the API. If you're
interested, I can post it.

[Dave]

Wow, first thanks for all the responses.

Ignacio, you are correct, I should have tested the class containing the
structure before slapping it into a service. I was reusing code from an
existing service that didn't have a separate test harness so I was
winging it and got burnt.

Chris, yes I would be curious to see the service install using the API.
Is there a particular reason you went that route? Once I fixed the
struct issue the installer worked fine.

I guess the thing that really bit me was that I was able to declare the
invalid struct but it wasn't until runtime that my error was caught
(I'm talking about not being able to use explicit offsets with
reference types rather than specifying UInt32 instead of UInt16). This
probably reflects a poor development approach on my part, plus coming
from a c++ background I did tend to rely on the compiler to highlight
this kind of mistake. I will assume that due to the way attributes are
implemented this kind of error is difficult to pick up at compile time.

So the approach I'm now taking is to ditch the struct and use
Buffer.BlockCop y() to get the values I need. I would be curious also to
know if there is a better approach to doing this transformation.
Basically I need to convert between 3 UInt16's and 6 bytes as a header
for a data packet.

Thanks and regards

[Chris Dunaway]

Dave wrote:

Chris, yes I would be curious to see the service install using the API.
Is there a particular reason you went that route? Once I fixed the
struct issue the installer worked fine.

My reason for going that route is that I wanted the service be able to
install itself without the need for an external utility. So with my
code, I can just call progname /install to install the service or
progname /uninstall to uninstall it.

Check this link:

http://tinyurl.com/7382d

[Dave]

Nice, thanks for posting Chris. And yes I can see the advantage to
being able to install the traditional way.

Dave