Re: How can be only one ? - C# Discussion Boards

Re: access memory within unmanaged dll

3-Sep-02 1:42

Hi, it seems you should be able to remove the array like:

[DllImport("theold.dll")]public static extern Int32 foo(out IntPtr messagePtr);
...
IntPtr messagePtr;
Int32 ret = foo(messagePtr);
Int16 size = Marshal.ReadInt16(messagePtr);
byte [] message = new byte[size];
Marshal.Copy(messagePtr,message,2,size); //remmeber that is only the size, and it is not included in byte[]

I'm interested, does this work too?

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Rüpel3-Sep-02 2:39

Rüpel

3-Sep-02 2:39

1. yep. out works indeed. good idea. but in the foo-call is to be inserted uswell.
2. no, the copy-call was ok, since the size-field is included (i.e. the value is at least 2 for the 2 size-bytes)

finally:

[DllImport("theold.dll")]
public static extern Int32 foo(out IntPtr messagePtr);
...
IntPtr messagePtr;
Int32 ret = foo(out messagePtr);
Int16 size = Marshal.ReadInt16(messagePtr);
byte [] message = new byte[size];
Marshal.Copy(messagePtr,message,0,size);

thx again for your help an ideas Rose | [Rose]

:wq

Re: access memory within unmanaged dll

leppie3-Sep-02 3:27

Re: How can be only one ?

3-Sep-02 3:27

Rüpel wrote:
but in the foo-call is to be inserted uswell.

oops Smile | :)

, happens when u write the code out of your head straight into the textbox Smile | :)

Rüpel wrote:
2. no, the copy-call was ok, since the size-field is included (i.e. the value is at least 2 for the 2 size-bytes)

But wont the fist 2 byte values (being a size value) affect the byte[]?

(oops another typo Smile | :)

, meant to do this)

byte [] message = new byte[size - 2];
Marshal.Copy(messagePtr,message,2,size);

byte [] message = new byte[size - 2];
Marshal.Copy(new IntPtr(messagePtr.ToInt32() + Marshal.SizeOf(typeof(byte))*2),message,0,size - 2);

I'm just interested Smile | :)

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Doing programs

suresh_sathya2-Sep-02 23:39

suresh_sathya

2-Sep-02 23:39

I want to know wheather we can write components using c# in place of ATL COM.i.e..is it possible to write everything whatever we do in ATLCom.

Re: Doing programs

Stephane Rodriguez.2-Sep-02 23:54

Stephane Rodriguez.

2-Sep-02 23:54

It depends if you intend to consume these components from unmanaged or managed code.

If that's managed code, then you are talking about the whole .NEt platform. A C# user control exposes interfaces that can be used in a VB.Net class.

If that's unmanaged code :
You'd better have good reasons to do so. ATL/COM components do not require the .Net framework to work.

And yes, there are tutorials about this in MSDN. You usually end up by doing a tlbexp.exe or regasm.exe (which is the opposite of importing a COM type-library).

And I swallow a small raisin.

How can be only one ?

candan2-Sep-02 16:42

candan

2-Sep-02 16:42

If I want my AP be only one ? How can I do this in C#? Confused | :confused:

There is an example in VC http://www.codeproject.com/threads/singleinstance.asp

Stephane Rodriguez.3-Sep-02 0:11

Stephane Rodriguez.

3-Sep-02 0:11

VC apps usually take advantage of mutexes. Go in the .Net framework MSDN doc, search "Mutex". Finish the implementation. Big Grin | :-D

And I swallow a small raisin.

Re: How can be only one ?

Christian Graus3-Sep-02 0:46

Christian Graus

3-Sep-02 0:46

When I saw this, I immediately thought of 'Highlander'.....

Christian

We're just observing the seasonal migration from VB to VC. Most of these birds will be killed by predators or will die of hunger. Only the best will survive - Tomasz Sowinski 29-07-2002 ( on the number of newbie posters in the VC forum )

Cats, and most other animals apart from mad cows can write fully functional vb code. - Simon Walton - 6-Aug-2002

Re: How can be only one ?

Richard Deeming3-Sep-02 1:00

Richard Deeming

3-Sep-02 1:00

This should do it:
http://msdn.microsoft.com/library/en-us/dndotnet/html/reaworapps1.asp[^]

Passing null

Nnamdi Onyeyiri2-Sep-02 8:09

2-Sep-02 8:09

I am using the ChangeDisplaySettings function from user32.dll, but when i need to reset to the default regitry settings, msdn says do ChangeDisplaySettings(null, 0); but it doesnt like the null value Frown | :(

what should i do?

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Paul Riley2-Sep-02 8:17

Paul Riley

2-Sep-02 8:17

What do you mean by "doesn't like"?

Paul

Nnamdi Onyeyiri2-Sep-02 8:25

2-Sep-02 8:25

it does not compile, as the function definition is as follows.

ChangeDisplaySettings(ref DEVMODE d, int flags);

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leppie2-Sep-02 9:17

2-Sep-02 9:17

DEVMODE is a struct.

1. just make another definition

ChangeDisplaySettings(object dummy, int flags);

or

2. change DEVMODE to a class with a sequential layout. Then you can pass null.

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Nnamdi Onyeyiri2-Sep-02 9:23

2-Sep-02 9:23

i have done the second one, but the app doesnt run now, wen you try and run it, it doesnt, nt even listed in the Process List. Confused | :confused:

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leppie2-Sep-02 12:11

2-Sep-02 12:11

I sent you VS solution, that happened to me too, seemed to be due not changing the enum declaration from ref DEVMODE to just DEVMODE ,its a class now so we dont need to. I however had to add the OutAttribute the the declaration.

Smile | :)

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Rickard Andersson²⁰2-Sep-02 10:45

Rickard Andersson²⁰

2-Sep-02 10:45

How about making the function unsafe?
Then use a pointer as parameter.
But that's maybe not possible when it's an imported function!?

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Display Mode

Nnamdi Onyeyiri2-Sep-02 2:22

2-Sep-02 2:22

have geen trying to get he current displaymode but have been unable, my latest attmpt was to try[^] and convert this articles code, but i had a little difficulty. I found the content of the DEVMODE struct on MSDN and put it into my code. I declare the EnumDisplaySettings like this

[DllImport("User32.dll")]<br />
public static extern bool EnumDisplaySettings(string lpszDeviceName, int iModeNum, DEVMODE lpDevMode);

then use it in code like this:

DEVMODE dm = new DEVMODE();
EnumDisplaySettings(null, -1, dm);

but i get the exception 'object reference not set to an instance of an object' yet clearly, a DEVMODE object has been initiated. Confused | :confused:

any help would be appreciated.

*sudden thought* in the decleration of the DEVMODE struct, on MSDN, a couple of the members where of tpye TCHAR, declared like this.

TCHAR  dmDeviceName[CCHDEVICENAME];<br />
TCHAR  dmFormName[CCHFORMNAME];

i couldnt find what CCHFORMNAME is so i just used the MarshalAs Attribute like this

[MarshalAs(UnmanagedType.ByValTStr, SizeConst=128)]  
public string  dmDeviceName;

for both, could that be the problem?

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"All programmers are playwrights and all computers are lousy actors."

leppie2-Sep-02 3:00

2-Sep-02 3:00

I think the exception lies with string lpszDeviceName being null.

You mite want to redefine:

[DllImport("User32.dll")]
public static extern bool EnumDisplaySettings(StringBuidler lpszDeviceName, int iModeNum, DEVMODE lpDevMode);

Then when calling do StringBuilder devname = new StringBuilder( insert const size here).

Also , many times you need to set the size of a struct. In this case, according to MSDN, you will need to.

Nnamdi Onyeyiri wrote:
i couldnt find what CCHFORMNAME is so i just used the MarshalAs Attribute like this

This you will find the value in the header files, so download the Platform SDK if you dont have it already.

Hope this helps

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Nnamdi Onyeyiri2-Sep-02 3:16

2-Sep-02 3:16

leppie wrote:
I think the exception lies with string lpszDeviceName being null.

i dont think so, i tried entering a value for that, and it did not work, it gavethe same exception. i used null, because that is what was used in the article i gave the link for.

leppie wrote:
This you will find the value in the header files, so download the Platform SDK if you dont have it already.

is that installed with the default settings for vs.net install?

leppie wrote:
Also , many times you need to set the size of a struct. In this case, according to MSDN, you will need to.

i didnt know about this, ill have a look now.

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"All programmers are playwrights and all computers are lousy actors."

leppie2-Sep-02 3:31

2-Sep-02 3:31

Nnamdi Onyeyiri wrote:
dont think so, i tried entering a value for that, and it did not work, it gavethe same exception. i used null, because that is what was used in the article i gave the link for.

Still try using StringBuilder as u CAN pass null as a value.

Nnamdi Onyeyiri wrote:
is that installed with the default settings for vs.net install?

If u install VC++ , else just look for a dir in program files with many *.h files Smile | :)

I had a look and that is a pretty viscious struct Smile | :)

. Im not sure what a BCHAR is though. Im gonna try do something in C# and see what i come up with. Can you perhaps mail me what u have done so far?

Cheers Smile | :)

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Nnamdi Onyeyiri2-Sep-02 3:39

2-Sep-02 3:39

leppie wrote:
I had a look and that is a pretty viscious struct . Im not sure what a BCHAR is though. Im gonna try do something in C# and see what i come up with. Can you perhaps mail me what u have done so far?

sure, but ill need your email address Smile | :)

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leppie2-Sep-02 4:02

2-Sep-02 4:02

DEVMODE dm = new DEVMODE();
dm.dmSize = (short)Marshal.SizeOf(typeof(DEVMODE));
int mode = 0;
while (EnumDisplaySettings(null, mode++, ref dm) != 0)
{
	Console.WriteLine("{0}x{1}, {2}bits {3}hz",
		dm.dmPelsWidth, dm.dmPelsHeight, dm.dmBitsPerPel, dm.dmDisplayFrequency);
}

[DllImport("user32.dll", CharSet=CharSet.Ansi)]
static extern int EnumDisplaySettings(StringBuilder devname, int mode, ref DEVMODE devmode);

public struct DEVMODE 
{
	[MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)]
	public string dmDeviceName; 
	public short dmSpecVersion; 
	public short dmDriverVersion; 
	public short dmSize; 
	public short dmDriverExtra; 
	public int  dmFields; 
	public short dmOrientation;
	public short dmPaperSize;
	public short dmPaperLength;
	public short dmPaperWidth;
	public short  dmScale; 
	public short  dmCopies; 
	public short  dmDefaultSource; 
	public short  dmPrintQuality; 
	public short  dmColor; 
	public short  dmDuplex; 
	public short  dmYResolution; 
	public short  dmTTOption; 
	public short  dmCollate; 
	[MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)]
	public string  dmFormName; 
	public short  dmLogPixels; 
	public int  dmBitsPerPel; 
	public int  dmPelsWidth; 
	public int  dmPelsHeight; 
	public int  dmDisplayFlags; //funny union??
	//public int  dmNup;
	public int  dmDisplayFrequency; 
	public int  dmICMMethod;
	public int  dmICMIntent;
	public int  dmMediaType;
	public int  dmDitherType;
	public int  dmReserved1;
	public int  dmReserved2;
	public int  dmPanningWidth;
	public int  dmPanningHeight;
}

This works Smile | :)

Note the union ???? looks like it combines 2 int 's ???

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Nnamdi Onyeyiri2-Sep-02 4:51

2-Sep-02 4:51

thanks a lot! ive been puzzled over this for the last few hours. Big Grin | :-D

leppie wrote:
This works Note the union ???? looks like it combines 2 int 's ???

im not sure what you mean.

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leppie2-Sep-02 5:02

2-Sep-02 5:02

Im not really sure what a union in C++ does, it appears to join 2 variables into one, hence the commented dmNup. Can anyone C++ person please explain this in C# terms?

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