Re: Marshalling unmanaged DLL - C# Discussion Boards

Re: connection error

Dave Kreskowiak5-Dec-07 5:43

Dave Kreskowiak

5-Dec-07 5:43

Try updating the MDAC components to the latest. YOu can get that here[^].

A guide to posting questions on CodeProject[^]

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007

Passing value types async

Andre Azevedo5-Dec-07 4:15

Andre Azevedo

5-Dec-07 4:15

Hi all,

Can anyone tell me what happens (in the stack context) to the value type "x" after Init() method has been terminated:

--------------------

delegate void TestDelegate(ref int x);

class Program
{

static void Main(string[] args)
{
Init();
Console.WriteLine("Waiting");
Console.Read();
}

static void Init()
{
int x = 123;
int y = 123;
int z = 123;

TestDelegate t = new TestDelegate(TestFunc);
t.BeginInvoke(ref x, null, null);
}

static void TestFunc(ref int x)
{
Thread.Sleep(1000);
Console.WriteLine(x);
}

}

--------------------

Thanks,

________________________________________________________________
There are 10 kind of people: those who knows binary and those who doesn't.

Re: Passing value types async

led mike5-Dec-07 5:17

led mike

5-Dec-07 5:17

It appears you need to do more studying to understand async delegate usage. See if this article helps

sorry, apparently nothing works on the site, here is the URL to the article

http://msdn.microsoft.com/msdnmag/issues/01/08/Async/[^]

Re: Passing value types async [modified]

Andre Azevedo5-Dec-07 6:37

Andre Azevedo

5-Dec-07 6:37

Thanks!
Looking at the article, I figure out that passing int ref parameter (like Figure 13 example) will cause the value to be boxed - if the value is assigned to a object field - or simply copied - if the value is assigned to a int field - just like my example does. D'Oh! | :doh:

Just assign some another value to "i" after BeginInvoke call and it will not affect the result.

The question is: Does the delegate class created has a "int" type or an "object" type to hold the value?

________________________________________________________________
There are 10 kind of people: those who knows binary and those who doesn't.

modified on Wednesday, December 05, 2007 2:44:19 PM

Marshalling unmanaged DLL

Dio225-Dec-07 4:05

Dio22

5-Dec-07 4:05

I'm trying to use P/Invoke to marshal some legacy code. I either get an "Entry Point Not Found" error, or a "Memory access violation"

I've run dumpbin on this dll, and i've verified that the entry point exists. I'm lost.

Here's the source for the function I'm exporting..

extern "C" BOOL FindUser2(char *cpUserFile, 
              char *cpPassword, 
              char *cpUserName, 
              char *cpUserPriveledge, 
              char *cpUserID, 
              char *cpComments, 
              BOOL *bUserActive,
              char *cpErrorReason)
{...}

Here's my pathetic attempt to marshal it.

[DllImport("WN_USER_SECURITY.dll",EntryPoint="FindUser2") ]
        public static extern bool FindUser2(
            [MarshalAs(UnmanagedType.LPArray)]char[] strFileName,
            [MarshalAs(UnmanagedType.LPArray)]char[] strUserPassword,
            [MarshalAs(UnmanagedType.LPArray)]char[] strUserName,
            [MarshalAs(UnmanagedType.LPArray)]char[] strUserPriveledge,
            [MarshalAs(UnmanagedType.LPArray)]char[] strUserID,
            [MarshalAs(UnmanagedType.LPArray)]char[] strUserComments,
            [MarshalAs(UnmanagedType.Bool)] bool bUserActive,
            [MarshalAs(UnmanagedType.LPArray)]char[] strErrorReason);

Re: Marshalling unmanaged DLL

Pete O'Hanlon5-Dec-07 4:08

Pete O'Hanlon

5-Dec-07 4:08

Try marshalling your char[] as StringBuilder objects instead.

Deja View - the feeling that you've seen this post before.

My blog | My articles

Re: Marshalling unmanaged DLL

m@u5-Dec-07 4:50

m@u

5-Dec-07 4:50

Hi
first, as pete pointed out already it's a good idea to pass the char* with a string builder.
second, the BOOL *bUserActive looks to me like a ref value. so you might have to change your call as follows:

[DllImport("WN_USER_SECURITY.dll",EntryPoint="FindUser2") ]
        public static extern bool FindUser2(
            StringBuilder strFileName,
            StringBuilder strUserPassword,
            StringBuilder strUserName,
            StringBuilder strUserPriveledge,
            StringBuilder strUserID,
            StringBuilder strUserComments,
            [In,Out /*this is optional*/]ref bool bUserActive,
            StringBuilder strErrorReason);

it might work without the marshalAs Attributes because on "normal" datatypes, the clr automatically marshals the data correctly.
hope this helps
m@u

Re: Marshalling unmanaged DLL

Dio225-Dec-07 5:42

Dio22

5-Dec-07 5:42

Well, I still can't get past the "Entry point not found" exception. I've examined the DLL using dumpbin and Dependency Walker, and they both show the entry point "FindUser2" as existing at ordinal 1. For some reason the C# app just wont see it.

Re: Marshalling unmanaged DLL

Andre Azevedo5-Dec-07 6:44

Andre Azevedo

5-Dec-07 6:44

Did you get the exception in application run or in method calling?

________________________________________________________________
There are 10 kind of people: those who knows binary and those who doesn't.

Re: Marshalling unmanaged DLL

Dio225-Dec-07 7:24

Dio22

5-Dec-07 7:24

The exception occurs when I try to call the method.

Re: Marshalling unmanaged DLL

Andre Azevedo5-Dec-07 8:50

Andre Azevedo

5-Dec-07 8:50

Dio22 wrote:
The exception occurs when I try to call the method

So the function is there. Maybe you´re checking another dll.

________________________________________________________________
There are 10 kind of people: those who knows binary and those who doesn't.

Re: Marshalling unmanaged DLL

Luc Pattyn5-Dec-07 8:06

Luc Pattyn

5-Dec-07 8:06

Hi,

here are some suggestions:

1.
make sure there is only one WN_USER_SECURITY.dll file.
Maybe you are looking at one file with dumpbin, but your app is looking at another (older) one,
hidden in the Windows PATH somewhere.

2.
Does the app find other methods in the DLL?
does another app work fine with that DLL?

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

this months tips:
- before you ask a question here, search CodeProject, then Google
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get
- use PRE tags to preserve formatting when showing multi-line code snippets

Re: Marshalling unmanaged DLL

m@u6-Dec-07 4:19

m@u

6-Dec-07 4:19

hmm.. i'm not a c++ guru, but i once wrote a little c++ demo lib that was callable from c# and i'm not sure if this is important, and if you can do anything about it but:

1) in my method-declaration i used the stdCall keyword:
void __stdcall foo(unsigned int *param1, unsigned char *param2, unsigned char *param3, void *Handle)
--> i think the default calling convention for pInvoked Method is stdCall so if it's not declared that way it might fail..
2) in the exports.def of the library i had to put this in order to make it work:

EXPORTS<br />
foo	@1

--> if this is missing, it might explain the EntrypointNotFound - exception

greets
m@u

General question about MS Certifications

allende5-Dec-07 3:32

allende

5-Dec-07 3:32

Hello friends,

I hope this is the right forum to place this question, if it isn't, please apologize me.

I'm thinking in taking the C# certification examinations and I need some help finding the right book or documentation to study.
If any of you did it before, perhaps can give a hand telling me the books you used so I can buy it.

Thanks a lot.

Re: General question about MS Certifications

Sathesh Sakthivel5-Dec-07 3:47

Sathesh Sakthivel

5-Dec-07 3:47

http://www.microsoft.com/learning/exams/70-315.mspx[^]

http://www.dhruvaraj.com/olbooks/MsTech/Wrox_Professional_ASP.NET_2.0_.htm[^]

SSK.

Anyone who says sunshine brings happiness has never danced in the rain.

Re: General question about MS Certifications

MaxRelaxman5-Dec-07 4:58

MaxRelaxman

5-Dec-07 4:58

My favorite book is Programming C# from O'Reilly. Actually I've never gone wrong by buying an O'Reilly book.
http://www.oreilly.com/pub/topic/csharp[^]

You may also want to look into training Videos. We just bought some for our new programmer. We're using AppDev
http://www.appdev.com/csharp.asp[^]

Re: General question about MS Certifications

allende5-Dec-07 7:44

allende

5-Dec-07 7:44

Thanks for all your answers. Help very appreciated.

I will check them and get the book.

pd: Any other opinion is welcome.

Writing text to images

adi.rusu5-Dec-07 3:20

adi.rusu

5-Dec-07 3:20

Hello.

I am trying to write the text given by the user onto an image and save the image. If i save it once using the Save method of the Bitmap object, it works. But if i try again, i get an exception because the file is locked. I have to restart the application to save the file again. Does anybody know a solution?

Thanks

Re: Writing text to images

J4amieC5-Dec-07 3:46

J4amieC

5-Dec-07 3:46

Yes, make sure you Dispose of any Bitmap or File you are using!

Re: Writing text to images

adi.rusu5-Dec-07 4:15

adi.rusu

5-Dec-07 4:15

I did that. Here is my code:

Font f = new Font("Arial", 48);
Bitmap b = new Bitmap("some path");
Graphics g = Graphics.FromImage(b);
g.DrawString(textBox.Text, f, Brushes.White, 50, 50);
g.Flush();
try
{
b.Save("result path", ImageFormat.Jpeg);
b.Dispose();
b = null;
pictureBox.Image = Image.FromFile("result path");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message); //Displays "A generic error occured in GDI+"
}

I wrote the message on the forum after i tried this code. So Dispose doesn't really work as I had expected. Any other ideas?

Re: Writing text to images

Luc Pattyn5-Dec-07 5:11

Luc Pattyn

5-Dec-07 5:11

Hi,

images that get created from a file, lock that file for as long as the Image exists.
This holds true for Bitmap b=new Bitmap(path) as well as pictureBox.Image = Image.FromFile(path).

As long as your PictureBox is showing an image, loaded from a file like that, you won't be
able to delete or modify that file.

There are basically two solutions:
1. load the image, copy it to a second image immediately (as in new Bitmap(image)), and dispose of the first image;
2. create a FileStream to the file, and load the image using FromStream, this does not lock
the file that your stream refers to.

FileStream stream=new FileStream(fileSpec, FileMode.Open, FileAccess.Read);
Image localImage2=Image.FromStream(stream);

Luc Pattyn [Forum Guidelines] [My Articles]

Convert a binary data received from serial port to its corresponding decimal value

anu9145-Dec-07 2:39

anu914

5-Dec-07 2:39

Dear All,

I'm really stuck with my serial communication algorithm.

I receive the binary number sent to the serial port properly as "1000001" when i check in the hyperterminal, but i cannot convert it to the corresponding decimal value using my C# program.

Any help regarding this will be really appreciated.

Thank you.

Re: Convert a binary data received from serial port to its corresponding decimal value

m@u5-Dec-07 2:54

m@u

5-Dec-07 2:54

Hi
Is this a string containing "10000001"? if so, and you want to convert it to an int or a long, you can use the Convert.ToInt32 or Convert.ToInt64 method:

long l = Convert.ToInt64("110101101",2);

greets
M@u

Re: Convert a binary data received from serial port to its corresponding decimal value

CKnig5-Dec-07 2:55

CKnig

5-Dec-07 2:55

oh my - never noticed that you can convert from different bases - thx.

Drag/drop component

Accius5-Dec-07 2:13

Accius

5-Dec-07 2:13

Hi,
i'm beginnig to write the code for a drag/drop component.Basically,i want to create a map-like control,where the user can drag & drop items chosen from a set.
So i will have a control's portion with the items to choose from (with a drag operation) and a "work" area where to drop the chosen items.
Now i'm concerned about various things(like zooming,handling the size of the map when there are many items in the map etc...),and,most important,i am still a newbie developer,so,before starting from scratch, i ask you:do you know some similar control/example that could put me on the right way?
Surely something similar to Microsoft Visio would help,but i need some sample code Smile | :)

Thanks in advance!

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