Re: ? : Operator - C# Discussion Boards

21-Jul-10 7:00

Hi , have a good day
Can anyone Explain for me what the meaning of this ?

a = b == null ? null : a.ToString();

P.S : for more information :

I use this component Example Code , and I need to understand it !
http://www.gemboxsoftware.com/help/html/M_GemBox_Spreadsheet_ExcelWorksheet_ExtractToDataTable.htm[^]

if (e.ErrorID == ExtractDataError.WrongType)
    {
      e.DataTableValue = e.ExcelValue == null ? null : e.ExcelValue.ToString();
      e.Action = ExtractDataEventAction.Continue;
    }

Please , Don't tell to Ask at Component Forum , due my question is C# syntax things
thank you

I know nothing , I know nothing ...

harold aptroot21-Jul-10 7:02

harold aptroot

21-Jul-10 7:02

It means

if (b == null)
    a = null;
else
    a = a.ToString(); //this rarely makes sense, didn't you mean b.ToString()?

But it's an expression instead of a statement.

I Believe In GOD21-Jul-10 7:06

21-Jul-10 7:06

Thank you so much , for this fast , great replay of yours ,

you saved me from headache D'Oh! | :doh:

I have voted for you

Rose | [Rose]

I know nothing , I know nothing ...

harold aptroot21-Jul-10 7:13

harold aptroot

21-Jul-10 7:13

Thanks

I Believe In GOD21-Jul-10 7:12

21-Jul-10 7:12

And yes I meant b.toString(); Smile | :)

I know nothing , I know nothing ...

Luc Pattyn21-Jul-10 7:02

Luc Pattyn

21-Jul-10 7:02

everything you should know about C# is in your C# book, in MSDN, in the C# specification[^], etc.

Hmmm | :|

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, and improve readability.

I Believe In GOD21-Jul-10 7:10

21-Jul-10 7:10

Thank you ,
But for a certain things MSDN is Yak !

http://msdn.microsoft.com/en-us/library/ty67wk28.aspx[^]

The conditional operator is right-associative. The expression a ? b : c ? d : e  is evaluated as a ? b : (c ? d : e), not as (a ? b : c) ? d : e.<br />
<br />
The conditional operator cannot be overloaded.

I know nothing , I know nothing ...

Roger Wright21-Jul-10 7:54

Roger Wright

21-Jul-10 7:54

You're right, and that's classic Microsoft - technically accurate, entirely useless information! Laugh | :laugh:

"A Journey of a Thousand Rest Stops Begins with a Single Movement"

Luc Pattyn21-Jul-10 8:05

Luc Pattyn

21-Jul-10 8:05

"you're in an airplane" kind of stuff?

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, and improve readability.

Roger Wright21-Jul-10 8:35

Roger Wright

21-Jul-10 8:35

Exactly!

"A Journey of a Thousand Rest Stops Begins with a Single Movement"

Eddy Vluggen21-Jul-10 9:12

Eddy Vluggen

21-Jul-10 9:12

Where is the Yak point? In all fairness, the first line of the document states;

txt

The conditional operator (?:) returns one of two values depending on the value of a Boolean expression.

Perfect logical KISS.

I are Troll Suspicious | :suss:

dan!sh 21-Jul-10 9:18

dan!sh

21-Jul-10 9:18

I do not understand why you think like that.

dan!sh 21-Jul-10 9:24

dan!sh

21-Jul-10 9:24

I guess you meant b.ToString there. If you did, you really don't need ternary operator. Convert.ToString would be enough.

yu-jian21-Jul-10 9:37

yu-jian

21-Jul-10 9:37

a = b == null ? null : a.ToString();

Means if b equals null then set a = null
else set a = a.ToString()

if code changed to following, I may understand it.

if (b == null)
{
a = null;
}
else
{
a = a.toString()
}

brunoseixas22-Jul-10 5:24

brunoseixas

22-Jul-10 5:24

? operator its like a IF-result statement.

look:

int x = 0;
int y = 1;

if(x > y) ? y++ : y--;

If x>y = true, y++.
If x>y = false, y--;

Stopping Process

anveshvm21-Jul-10 6:06

anveshvm

21-Jul-10 6:06

I am using FFMPEG for streaming operations.
(https://www.transferbigfiles.com/a3209f95-ffcc-4c82-b722-041a24c26ec1?rid=KsWHbP3Lo/rxGH4YHVVVtA%3d%3d)

I started it using the following program

Process myProcess = new Process();
myProcess.StartInfo.FileName = @"ffmpeg.exe";
myProcess.StartInfo.UseShellExecute = false;
myProcess.StartInfo.RedirectStandardInput = true;

myProcess.StartInfo.Arguments = "-i input.avi -vcodec copy -acodec copy output.avi";
myProcess.Start();

StreamWriter myStreamWriter = myProcess.StandardInput;

myStreamWriter.Write("113"); //using ascii of q
myStreamWriter.Flush();

myStreamWriter.Write('q');
myStreamWriter.Flush();

myStreamWriter.Close();


myProcess.WaitForExit();
myProcess.Close();

My intention is to close the program when I send "q" from the program (I meant a graceful exit without making any error).

But I can't close it by sending 'q' character or its corresponding ascii. When I run the program from the command line and I press q in the keyboard, program immediately gets closed.

Can you pls. help me?

Thank you

regards
anvesh

PIEBALDconsult21-Jul-10 7:54

21-Jul-10 7:54

anveshvm wrote:
Can you pls. help me?

I believe so; see my ProcessCommunicator[^] article.

anveshvm22-Jul-10 2:36

anveshvm

22-Jul-10 2:36

Thanx for the reply,

Its actually a nice article. But I couldn't solve my issue using it.

A carriage return is not necessary for this application to close. Pressing a 'q' itself (from keyboard) will give give graceful end to the program. I need not press an additional enter key.

And as an additional step of precaution, I made my own console program which requries a 'q' followed by carriage return to close the application, and it worked fine when I use WriteLine from .NET

What might be the issue? Its only for ffmpeg that I can't send input stream to. I am anxious to know what might be the issue?

PIEBALDconsult22-Jul-10 3:21

22-Jul-10 3:21

I don't know, I'm stumped. But maybe the program reads something internal instead of the input stream.

What is ffmpeg? Maybe I can try it.

anveshvm22-Jul-10 4:16

anveshvm

22-Jul-10 4:16

ffmpeg produces libraries and programs for handling multimedia. We can convert media files into different formats using ffmpeg. It can also record live streams from a camera in different formats.

I am attaching the ffmpeg.exe here.
https://www.transferbigfiles.com/a3209f95-ffcc-4c82-b722-041a24c26ec1?rid=KsWHbP3Lo/rxGH4YHVVVtA%3d%3d[^]

Here in my code i just copy the audio and video codecs of a file (input.avi) into another file(output.avi). Different parameters can be added in this command, but I just consider the basic operation here.

            Process myProcess = new Process();
            myProcess.StartInfo.FileName = @"ffmpeg.exe";
            myProcess.StartInfo.UseShellExecute = false;
            myProcess.StartInfo.RedirectStandardInput = true;

            myProcess.StartInfo.Arguments = "-i input.avi -vcodec flv -acodec copy output.flv";
            myProcess.Start();

            StreamWriter myStreamWriter = myProcess.StandardInput;

            myStreamWriter.Write("113"); //using ascii of q
            myStreamWriter.Flush();

            myStreamWriter.Write('q');
            myStreamWriter.Flush();

            myStreamWriter.Close();


            myProcess.WaitForExit();
            myProcess.Close()
;

If i run the pgm ( ffmpeg.exe should be placed in same foldr) it starts the conversion from avi to flv.
When I press [q] the pgm gets closed gracefully.

But I I am not being able to close it by sending 'q' character or its corresponding ascii. Confused | :confused:

PIEBALDconsult22-Jul-10 3:35

22-Jul-10 3:35

anveshvm wrote:
WriteLine

Oh, yeah, that may actually send a LINEFEED and a CARRIAGE-RETURN. If so, you would have to set the NewLine property.

PIEBALDconsult21-Jul-10 17:36