Mailslot possible with proper PInvoke?

[Ted]

Is it possible to use mailslots in .NET using PInvoke?

I have a VC++ 6.0 based app that creates and listens to a
mailslot. I have a second VC++ 6.0 based app that opens
the mailslot and writes to it successfully. So this stuff
works.

Additionally, I have a VB.NET app that opens the mailslot
successfully using CreateFile() (with PInvoke). What looks
like a proper handle is returned and there is no error.
(Marshal.GetLastWin32Error() returns 0).

However, when I try to use this handle (VB.NET app) with
WriteFile() (using PInvoke) the write fails with error
code 0x06, which is "The handle is invalid".

I have tried multiple versions of PInvoke signatures,etc.
with the same result.

IS IT AT ALL POSSIBLE TO USE MAILSLOTS WITH .NET?

Thank you,
Ted

[Mattias Sjögren]

Ted,

I have tried multiple versions of PInvoke signatures,etc.
with the same result.
Please post your declarations so we can have a look.

IS IT AT ALL POSSIBLE TO USE MAILSLOTS WITH .NET?

I don't see why not.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/
Please reply only to the newsgroup.

[Ted]

Mattias,

I have also tried to pass the handle to WriteFile using a
ByVal parameter, but had the same result. (bad handle)

Thanks,
Ted
I have included my VB.NET declarations:

-----------------------------------------------------------
<DllImport("kernel32.dll", _
CharSet:=CharSet.Ansi, _
EntryPoint:="CreateFileA", _
ExactSpelling:=True, _
SetLastError:=True)> _
Public Shared Function CreateFile(
ByVal lpFileName As String, _
ByVal dwDesiredAccess As Int32, _
ByVal dwSharedMode As Int32, _
ByRef lpSecurityAttributes As IntPtr, _
ByVal dwCreationDisposition As Int32, _
ByVal dwFlagsAndAttributes As Int32, _
ByRef hTemplateFile As IntPtr) As IntPtr
End Function

<DllImport("kernel32.dll", _
EntryPoint:="WriteFile", _
ExactSpelling:=True, _
SetLastError:=True)> _
Public Shared Function WriteFile(
ByRef hFile As IntPtr, _
ByRef lpBuffer As IntPtr, _
ByVal nNumberOfBytesToWrite As Int32, _
ByRef lpNumberOfBytesWritten As Int32, _
ByRef lpOverLapped As IntPtr) As Integer
End Function
-----------------------------------------------------

-----Original Message-----
Ted,

I have tried multiple versions of PInvoke signatures,etc. with the same result.

Please post your declarations so we can have a look.

IS IT AT ALL POSSIBLE TO USE MAILSLOTS WITH .NET?

I don't see why not.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/
Please reply only to the newsgroup.
.

[Mattias Sjögren]

Ted,

With the exception of lpNumberOfBytesWritten, all parameters you
currently have declared ByRef should be ByVal.

Also, FWIW, explicitly calling the ANSI version of CreateFile hurts
performance on NT based Windows versions. It's generally better to use
CharSet.Auto.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/
Please reply only to the newsgroup.

[Ted]

Mattias,

I found my bug, thank you VERY MUCH for your help.
Ted

-----Original Message-----
Mattias,

I have tried a number of ways including as you described:

With the exception of lpNumberOfBytesWritten, all parameters you

currently have declared ByRef should be ByVal.

The result is the same. The handle used with WriteFile()
returns an invalid handle error.

Have you ever used mailslots with .NET successfully? Do
you have a small example of code using mailslots

with .NET?

Thanks,
Ted

-----Original Message-----
Ted,

With the exception of lpNumberOfBytesWritten, all

parameters you

currently have declared ByRef should be ByVal.

Also, FWIW, explicitly calling the ANSI version of

CreateFile hurts

performance on NT based Windows versions. It's generally

better to use

CharSet.Auto.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/
Please reply only to the newsgroup.
.

.