Hello,

I have to make a DDE-Connection from dot.net (as a Client).
The DDE-Implementation from Brian Gideon (http://www.ozemail.com.au/
~markhurd/vbnetdde.zip)
works, but I still need a function to list all avaiable DDE-
applications.

I found this example in C:
http://msdn2.microsoft.com/en-us/library/ms997517.aspx
Sourcecode:
www.microsoft.com/downloads/details.aspx?familyid=F89F86DF-04D7-4464-AB21-9EB1679F41BD&displaylang=en

Who can help me to migrate the "list of DDE-Applications" to C#
(see DdeConnectList and DdeQueryNextServer)

Manfred Kiener

Actually, that one is not mine.  I moved mine from the gotdotnet site
to http://www.codeplex.com/ndde recently.



Mine doesn't either really.  It does have an API that raises an event
when a new server registers using the DDEML, but that's it.  Well,
then there's the DdeMonitor class which monitors all activity on a
system, but honestly, I can't remember what all it can monitor.  DDE
is nearly dead so I don't really support the library anymore.  In
fact, it's been almost 2 years since I did anything with it.


I have a lot of experience using DDE in C# so I could help if you have
specific questions, but I really recommend moving away from the
technology altogether.

A C# DDEML solution would be better for you, but my sample above already
enumerates all available DDE applications because if follows the basic
DDE protocol when initiating a connection: It broadcasts to all windows
a request to respond to DDE. You could accumulate the responses and not
(necessarily) start a connection.

Regards,
Mark Hurd, B.Sc.(Ma.)(Hons.)

Thank you for your answers.

I know that DDE is a dead tecnology, but in my case I have no chance
to change the technology.

I googled a lot about DDE and I am a little bit confused:
What exact is DDEML?

Is DDEML to use e.g.

[DllImport("user32.dll", EntryPoint="DdeInitialize",
CharSet=CharSet.Ansi)]
public static extern int DdeInitialize(ref int pidInst,
DdeCallback pfnCallback, int afCmd, int ulRes);

This was my understanding from DDEML, but Mark says:

Marks sample is very complex and uses "DdeInitialize" too, is there an
easier way to be an DDE-Client?

@Mark:

I adapted the sample to be a DDE-Client for a barcode tool from will-
software
(www.will-software.com) and it works very fine (to be a DDE-Client for
this barcode-Software is ONLY A SAMPLE,
I need DDE to simulate a 15 years old technoligie which can control
DDE-Servers in many cases).
I tried to debug your sample, but I didn't find what you mean.
Could you give me more hints (e.g. a methode-name where the broadcast
is realized?)

@Brian:
Yes, I have a specific question.
But the sample is difficult to isolate to print the sourcecode here.

I call DdeConnectList (from user32.dll) and get a integer-Handle for a
list of DDE-Application (I belive!).
With DdeQueryNextServer I get exact the same number of int-handles (in
my case I got 4 int-handles), as the c++ - Tool.
(Folders, PROGMAN, Shell, Winword)
But I can not resolve the int-handles e.g. to the application-Name
(DdeQueryString), may be there ist only a little mistake with the call
and interop.

Maybe if you could spent 10 minutes of your time you will find the
error.
In this case I would send you the complete Sample-solution (just a few
KB)

Thank you and regards,

Manfred Kiener

Dynamic Data Exchange Management Library.  It encapsulates a lot of
the complexities of passing messages back and forth between
applications.


Yes, DdeInitialize is part of the DDEML.


I didn't see the call in his example, but then again I didn't look
very closely.  He's probably mixing the DDEML with the raw DDE message
protocol which, as I understand, should be perfectly acceptable.

As far as creating a DDE client easily...have you looked at the
library I provide?  To request data from a server the code would look
like the following.

DdeClient client = new DdeClient("myserver", "mytopic");
client.Connect();
string data = client.Request("myitem", 60000);

It can't get much easier than that.


You talk about controlling a server...that's usually done by doing a
DDE execute.  The library I provide supports that easily as well with
the DdeClient.Execute method.


DdeConnectList and DdeQueryNextServer are a little complicated to
use.  I'm still unclear as to why you want to use them.  Can you
clarify?

Hello,


Brian: yes, you are right. At my first message I talked about your
NDDE but
write the linkt to Marc's sample. Sorry
I realized that yesterday.

This solution to get "a list of DDE-Servers" works
(in context with the NDDE-library)


I Changed this definitions in DDEML.CS:

public static extern IntPtr DdeConnectList(int idInst, IntPtr
hszService, IntPtr hszTopic, IntPtr hConvList, ref
NDde.Foundation.Ddeml.CONVCONTEXT pCC/*IntPtr pCC*/);
public static extern int DdeQueryConvInfo(IntPtr hConv, int
idTransaction, ref CONVINFO pConvInfo/*IntPtr pConvInfo*/);


I added this in DDEMLClient.cs
public string[] GetListOfDdeServer()
{
ArrayList DdeServers = new ArrayList();
IntPtr hszSystem =
Ddeml.DdeCreateStringHandle(_InstanceId,"System",Ddeml.CP_WINANSI);

NDde.Foundation.Ddeml.CONVCONTEXT pCC = new
NDde.Foundation.Ddeml.CONVCONTEXT();
pCC.cb = (ushort)Marshal.SizeOf(pCC);
IntPtr hConvList =
Ddeml.DdeConnectList(_InstanceId,IntPtr.Zero,hszSystem,
IntPtr.Zero, // new list
ref pCC); // default context
Ddeml.DdeFreeStringHandle(_InstanceId,hszSystem);
//
// Walk the list adding the server names to our listbox
//
IntPtr hConv = IntPtr.Zero;

Ddeml.CONVINFO pConvInfo = new Ddeml.CONVINFO();
pConvInfo.cb = (ushort)Marshal.SizeOf(pConvInfo);

while((hConv = Ddeml.DdeQueryNextServer(hConvList,hConv)) !
= IntPtr.Zero)
{
int ui =
Ddeml.DdeQueryConvInfo(hConv,Ddeml.QID_SYNC,ref pConvInfo);

StringBuilder psz = new StringBuilder(255);
Ddeml.DdeQueryString(_InstanceId,
(IntPtr)pConvInfo.hszSvcPartner,psz,psz.Capacity,Ddeml.CP_WINANSI);

DdeServers.Add(psz.ToString());
Debug.WriteLine(psz.ToString());
}
//
// Free the list handle
//
Ddeml.DdeDisconnectList(hConvList);

return (string[])DdeServers.ToArray(typeof(string));
}

It was i little "try and error" (e.g. Thread-Handling), but now it
works "good enought"

@Brian, @Marc:
thank you for your help.

regards
Manfred Kiener

Thanks Manfred.  If DDE were not already nearly defunct and if I
actually had the motivation to keep supporting NDde I'd probably add
that method and publish a new release :)

Hi, Manfred,

I am sorry to bother you, but I found the following thread online, and
I am having issues similar to yours:

http://groups.google.com/group/microsoft.public.dotnet.framework.interop/browse_thread/thread/d6c9031c0aafa0d5/aa9f445e0718167f#aa9f445e0718167f

, and I see that you have added a very useful function (to the great
NDDE library) that is supposed to list all the available DDE server
names.

I have 2 questions, if you don't mind:

1) How do you properly call this function?  (examples?)
2) How can you connect to two different DDE servers which provide the
same DDE server name? I basically start two apps that both provide the
same DDE Server names, and I can't distinguish between them with the
regular DDEClient, but I want to connect to both of them. :(

Thank you!

Hello,

1) It is a litte bit tricky because of multithreading. Please email me
you still need help
2) I am not shure if it is possible to connect to two applications
with the same name.

Manfred Kiener

I need to create and use a DDE from within my WPF app, because I need to get and send data to an older simulator (a VisSim simulation).  VisSim supports creating a bi-directional DDE connection



What is the best way to do this?



Thanks!

Peter