Managed C++/CLI

OleDbCommand - peculiar issue

22-Jul-02 15:59

LOL

You wicked wicked man!!! Wink | ;-)

Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Re: Palm Os programming

ib04212923-Jul-02 6:43

ib042129

23-Jul-02 6:43

I don't think that's what the lounge is for.

Nish Nishant19-Jul-02 3:21

19-Jul-02 3:21

I had a table called user and it had a field called password. My SQL worked when directly executed into Access XP, but failed via OleDbCommand. Finally I had to rename the table User to Usr and the field password to passwd!

Does User and password have any special meaning to OleDbCommand or is this another MC++ issue????

I don't remember similar issues with C# Frown | :-(

Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

How to wrap lines?

Nish Nishant19-Jul-02 2:49

19-Jul-02 2:49

If I have a long string :-

"aaa.........lonnnggg............bbb"

and I want to write it as

"aaa........"
"...longggg..."
"...bbb"

I get a compile error of "newline in constant"

I remember being able to do this in VC++ 6!

What do I add as a line break character to do this in VC++ 7 for an MC++ project?

Regards
Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Re: How to wrap lines?

Nish Nishant19-Jul-02 2:51

Design issue - OleDbConnection

19-Jul-02 2:51

Kindly ignore post!!!
I had an additional " Blush | :O

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Re: How to wrap lines?

ColinDavies19-Jul-02 19:22

ColinDavies

19-Jul-02 19:22

Don't ya hate it when that happens.

Regardz
Colin J Davies

Sonork ID 100.9197:Colin

I am sick of fighting with Martin, I think I will ignore his posts from here on in, and spend the time working on articles instead.

Christian Graus

Nish Nishant19-Jul-02 2:43

19-Jul-02 2:43

Let's say we have a class A that wraps a DB table. Now suppose this has an Add method, should we use a OleDbConnection local to that function to do the insert? Or should we have a OleDbConnection member for the class A and open it in the constructor and kill it in the destructor. The Add function is an infrequently used function. A is a remotable object and my worry is that it might be kept alive too long and in such cases if there is a network outage or something, I am scared that the class will be destroyed out of the blue and the DB might not be closed properly.

Any suggestions are welcome
Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Alexandru Savescu19-Jul-02 3:57

19-Jul-02 3:57

You may be better off using a DataSet. It caches data from the server and you can store it on the client (Assume you connect to a data source and display everything in a data grid for example)

Then you will perform any operations on the client and update everything in the end. Thus, you do not have to worry about the connection being help up.

For additional info on datasets check my article here.

I hope that helps.

Best regards,
Alexandru Savescu

Nish Nishant19-Jul-02 4:04

19-Jul-02 4:04

Problem is that the DB connection is on the remoting server and it's the client that invokes calls remotely. The kind of app I have in mind had an issue that a client might connect and then disconnect only after 6 hours or even a full day. I am worried about a connection being alive for that long and timing out in between. Datasets also don't seem same for this. If a network failure occurs, then I won't be able to flush the data in time.

Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Alexandru Savescu19-Jul-02 4:15

19-Jul-02 4:15

Well, having a connection open for 6 hours non-stop is bad in every sense you want: bad design, bad implementation etc. The Internet itself was not designed to keep connections alive (see the IP protocol). You have every reason for connections alive that long. You don't speak on a phone that much (and a phone keeps a connection open)

Anyway, datasets may be a better option. You may from time to time flush data in backgound (say every 30 minutes). Also, if data is not flushed on time (or timeout occurs when updating) then you can catch an exception and always retry.

Best regards,
Alexandru Savescu

Nish Nishant19-Jul-02 4:23

Multiple objects? Or one BIG object? A design question!

19-Jul-02 4:23

It's not about bad design here Alex. I don't have a choice here. A remote client may do what it wants to. We cannot dictate to it to close after a minimum while Frown | :-(

I like your periodic flush idea. I'll do that.

And yeah, I'll take a look at your Dataset article too Smile | :)

Thanks

Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Nish Nishant18-Jul-02 1:40

Marshaling an interface between threads in a process

18-Jul-02 1:40

If I need to remote 3-4 objects, should I start as many TcpChannels as there are objects and listen on them, meaning I have 4 ports open; or is it better design to have one master object which is remoted and which has methods to return each of the n number of objects?

Regards
Nish

p.s. The context is .NET remoting using MC++ and the BCL

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Michael Mac14-Jul-02 10:54

Michael Mac

14-Jul-02 10:54

I've got some problem trying to marshal an interface between threads in a process. WTF | :WTF:

In Win32 app I can call CoMarshalInterThreadInterfaceInStream to marshal and
CoGetInterfaceAndReleaseStream to unmarshal or use Global Interface Table
but I don't know how to declare this functions/Com class in the
.NET. Or mayby there is another solution build-in the framework.

Can you guys write some example how to use this functions/COM class

I'll appreciate it.
Thanks in advance

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Re: Marshaling an interface between threads in a process

Rama Krishna Vavilala16-Jul-02 11:10

Rama Krishna Vavilala

16-Jul-02 11:10

In my opionion the framework takes care of that for you.

Step back, rub your eyes, take a deep breath, stretch a bit, and reflect on the relative importance of CP, CG, the age / travel time sustained by supposedly 'fresh' cheese curds, and Life in General. - Shog⁹

Re: Marshaling an interface between threads in a process

Michael Mac17-Jul-02 0:16

Michael Mac

17-Jul-02 0:16

That's right. Smile | :)

I found the answer in the .Net SDK.
But there is one requirement - both threads must be in the STA apartment, otherwise the function call on the interface will fail.

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Excel format IO

ILLCOMM10-Jul-02 10:22

ILLCOMM

10-Jul-02 10:22

i need to take data from an existing excel document use it to match something then place the output in a new column in the original excel document. is this possible? i program in c++ using the g++ complier in a unix environment...

Re: Excel format IO

Carlos Antollini10-Jul-02 10:30

Carlos Antollini

10-Jul-02 10:30

It's very hard, to say, but try here

Regards

Carlos Antollini.
Sonork ID 100.10529 cantollini

Copy a CString to a Stream*

Alexandru Savescu9-Jul-02 3:20

9-Jul-02 3:20

Hi! I am using an application that is using both managed to unmanaged code.

I want to copy data from a CString to a Stream* (it may be MemoryStream or BufferedStream - whichever is faster).

Can anyone help? Thanks

Best regards,
Alexandru Savescu

Nish Nishant9-Jul-02 17:27

9-Jul-02 17:27

Convert the CString to a String* and then pass the String* to the Stream*

Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Alexandru Savescu9-Jul-02 22:06

9-Jul-02 22:06

Sorry Nish, it does not work. Here is what I did:

CString str = "aaaa":
String* str1 = new String (str);
MemoryStream* mem1 = new MemoryStream (str1, false);

and the result is:

c:\Work\Test.cpp(332): error C2664: 'System::IO::MemoryStream::MemoryStream(unsigned char  __gc[],bool)' : cannot convert parameter 1 from 'System::String __gc *' to 'unsigned char  __gc[]'

I found an work arround that compiles and works but I hate it:

MemoryStream* mem = new MemoryStream (n) ;// specify the size
for (int i = 0; i < n; i++)
  mem->WriteByte (str[i]);

Do you have another solution?
Thanks!

Best regards,
Alexandru Savescu

Michael Mac14-Jul-02 11:04

Michael Mac

14-Jul-02 11:04

Try this:

CString str = "aaaa";
String* strText = new String (str);
Byte message[] = System::Text::Encoding::ASCII->GetBytes( strText );
MemoryStream* sStream = new MemoryStream( message );

If you want to use diffrent encoding replace the bold text with the appropriate encoding like: Unicode, UTF7 or UTF8.

I should work Smile | :)

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Alexandru Savescu14-Jul-02 20:17