C# and COM and return values. (newby question) - C# Discussion Boards

C# and COM and return values. (newby question)

20-Jun-08 8:13

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Maximilien20-Jun-08 8:06

Maximilien

20-Jun-08 8:06

(Just learning C# and trying to do what I did in C++ with C#, and this is not an urgent question)

I have a COM "server" with a method FileOpen which returns a HRESULT :

...
	[id(2), helpstring("Open a file.")] HRESULT FileOpen([in] BSTR filename);
...
	STDMETHOD(FileOpen)(BSTR filename);
...

When I added the reference to my COM stuff in my sample C# project, the method is listed as Void FileOpen(...) (when I look at the browser in the IDE), I loose the return code.

Am I missing something ? As far as I understand, the COM is wrapped in a proxy (Runtime callable Wrapper) of some kind; I assume this strips the return value from the prototype ?

Thanks for any help, hints, tips, or links (or even better) for google keywords that can help me in my searches.

Max.

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leppie20-Jun-08 8:15

20-Jun-08 8:15

Maximilien wrote:
this is not an urgent question

That makes this a very very good question Smile | :)

Maximilien wrote:
the method is listed as Void FileOpen(...) (when I look at the browser in the IDE), I loose the return code.

That is correct. AFAIK, the COM wrapper will check the HRESULT and auto throw the COM Exception, kinda neat, hey? Poke tongue | ;-P

(I could be completely wrong too, hehe)

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Maximilien20-Jun-08 8:36

Maximilien

20-Jun-08 8:36

That's what I just discovered, and above all, there is a HResult property in the System.Exception

Thanks.

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Brady Kelly20-Jun-08 8:56

Brady Kelly

20-Jun-08 8:56

Innit kewl?

Luc Pattyn20-Jun-08 9:07

Luc Pattyn

20-Jun-08 9:07

baai koel

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leppie20-Jun-08 9:25

20-Jun-08 9:25

ja lekker

hehe

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leppie20-Jun-08 9:27

Cannot seem to be able to write a byte[] to a file

20-Jun-08 9:27

Well I didnt really know, well maybe I did, I have been grinding on .NET for almost 7 years so I cant really recall. Anyways just follow the element of least surprise principle Smile | :)

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LCI20-Jun-08 7:56

LCI

20-Jun-08 7:56

I am using StreamWriter to write out some jpeg data in byte[] to a file.
The result of my file is always "System.Byte[]"

byte[] jpegData = new byte[img.Length];
jpegData = Convert.FromBase64String(img);
using (StreamWriter sr1 = new StreamWriter("C:\\123.jpg"))
{

sr1.Write(Convert.ToString(jpegData));
sr1.Flush();
sr1.Close();
}

Re: Cannot seem to be able to write a byte[] to a file

Giorgi Dalakishvili20-Jun-08 8:06

Giorgi Dalakishvili

20-Jun-08 8:06

Why don't you use BinaryWriter instead?

Giorgi Dalakishvili

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Re: Cannot seem to be able to write a byte[] to a file

leppie20-Jun-08 8:12

Re: Cannot seem to be able to write a byte[] to a file

20-Jun-08 8:12

System.IO.File.WriteAllBytes()

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LCI20-Jun-08 8:22

LCI

20-Jun-08 8:22

Thanks, this worked great.

Do you know how i would write this jpeg data in the form of byte[] to a form instead of to a file? So in other words i would like to display jpg on the form. Would i need a picture control?

Re: Cannot seem to be able to write a byte[] to a file

leppie20-Jun-08 8:27

Re: Cannot seem to be able to write a byte[] to a file

20-Jun-08 8:27

You can simply do:

myform.BackgroundImage = Image.FromStream(new MemoryStream(jpegbytes));

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LCI20-Jun-08 8:32

LCI

20-Jun-08 8:32

thanks, i'll try that.
If i would like to put 4 images on the form, i would have to write them to a control write?

Hex String into number

aman200620-Jun-08 7:26

aman2006

20-Jun-08 7:26

Hello I have one question regading the conversion of Hex String into Decimal number.
Hex Number is in format

“aaaaaa”

This 24-bit field is the direction “A” counter stored LS-byte first.

Example is, take this hex string "100000" which is decimal equivalent is 16
But i don't know how to convert this number into decimal number. If i give this number to C# function it is not giving me the exact 16 equivalent.

Another exanples are
060100= 262
1C0000= 28

Can any body please help me how to convert these numbers into decimal equivalent using C#

Thanks
Shailesh

snorkie20-Jun-08 7:47

snorkie

20-Jun-08 7:47

int.Parse(hexValue, System.Globalization.NumberStyles.HexNumber);

Hogan

aman200620-Jun-08 7:56

aman2006

20-Jun-08 7:56

Thanks Hogan but i think you did not read the question. It is writing the LS byte first when i use your solution it is giving me 1048576 not 16.

Any body please help me

Thanks in advance
shailesh

snorkie20-Jun-08 8:05

snorkie

20-Jun-08 8:05

shailesh,

Sorry about that. I usually thing of "LS" as a different model of a car, not part of definition of the problem. I assume LS means "Left Side" then?

Hogan

leppie20-Jun-08 8:17