Re: String, Why does this work?? - C# Discussion Boards

BillWoodruff30-Apr-14 9:58

BillWoodruff

30-Apr-14 9:58

Because the designers of .NET C# decided that the "+" operator between strings ... if the item before the plus-sign is a string ... would automatically invoke conversion of all items to the right of the plus-sign to Type String.

You can see an even more dramatic example of this if you execute:

int v = 1;
Int32 w = 2;
Int64 x = 3;
double y = 4;
float z1 = 5;
Single z2 = 6;
string yString = "" + v + w + x + y + z1 + z2;

Yep, it compiles. So, you can infer that ... given a lack of parentheses) arithmetical operator evaluation for the plus sign is "turned off."

If you think this is kind of strange, you may not be alone Smile | :)

“I speak in a poem of the ancient food of heroes: humiliation, unhappiness, discord. Those things are given to us to transform, so that we may make from the miserable circumstances of our lives things that are eternal, or aspire to be so.” Jorge Luis Borges

GrooverFromHolland30-Apr-14 10:16

GrooverFromHolland

30-Apr-14 10:16

Thank You for your explanation,

Learn something every day.

thanks

0200 A9 23
0202 8D 01 80
0205 00

Rob Philpott1-May-14 1:51

Rob Philpott

1-May-14 1:51

Thing of beauty, .NET.

Regards,
Rob Philpott.

writing to a file while Looping

Alan N1-May-14 0:58

Alan N

1-May-14 0:58

The concatenation operators are replaced by calls to one of the overloaded string.Concat methods. There are versions with string or object parameters, e.g Concat(string, string, string), Concat(object, object, object), and if possible the more efficient (string, string, ...) versions will be used.

This gives us, well me really, the opportunity to play with ILDASM and have a look at what the C# compiler decides to do.

private static String StringConcat(String a, String b, String c) {
  return a + b + c;
}

private static String ObjectConcat(String a, int b, DateTime c) {
  return a + b + c;
}

and the IL shows the use of the different Concat methods.

.method private hidebysig static string  StringConcat(string a,
                                                     string b,
                                                     string c) cil managed
{
  // Code size       9 (0x9)
  .maxstack  8
  IL_0000:  ldarg.0
  IL_0001:  ldarg.1
  IL_0002:  ldarg.2
  IL_0003:  call       string [mscorlib]System.String::Concat(string,
                                                              string,
                                                              string)
  IL_0008:  ret
} // end of method ConcatTest::StringConcat

.method private hidebysig static string  ObjectConcat(string a,
                                                      int32 b,
                                                      valuetype [mscorlib]System.DateTime c) cil managed
{
  // Code size       19 (0x13)
  .maxstack  8
  IL_0000:  ldarg.0
  IL_0001:  ldarg.1
  IL_0002:  box        [mscorlib]System.Int32
  IL_0007:  ldarg.2
  IL_0008:  box        [mscorlib]System.DateTime
  IL_000d:  call       string [mscorlib]System.String::Concat(object,
                                                              object,
                                                              object)
  IL_0012:  ret
} // end of method ConcatTest::ObjectConcat

Alan.

Kasun Liyanage30-Apr-14 7:35

Kasun Liyanage

30-Apr-14 7:35

Hi all.

I need to write to a file --file names-- while looping a folder. So i did this:

string foldername = this.srcfbdlg.SelectedPath;

                StreamWriter sw = new StreamWriter("data.txt", true);

                var txtFiles = Directory.EnumerateFiles(foldername, "setup.exe", SearchOption.AllDirectories);

                foreach (string currentFile in txtFiles)
                {
                    string fileName = currentFile.Substring(foldername.Length + 1);
                    File.AppendAllText("data.txt", fileName);
                }

The problem is, while looping, AppendAllText() gives me the error "File cannot be accessed. I think that's because while looping the writing process overlaps, hence the bug. Is there a way around, without like making a timer to write or something?

Thanks for any reply guys.

Re: writing to a file while Looping

OriginalGriff30-Apr-14 8:07

OriginalGriff

30-Apr-14 8:07

OK...you can't see the problem yourself?

You have two different methods of adding data ready and in use in that code:

StreamWriter sw = new StreamWriter("data.txt", true);

Sets up sw to append to the file data.txt - which means opening the file and acquiring an exclusive lock so the file content can;t be changed while you are writing to it.
Then:

File.AppendAllText("data.txt", fileName);

Which tries to open the file data.txt for append by acquiring an exclusive lock so the file content can;t be changed while you are writing to it.

And fails, because there already is an exclusive lock open on the file...by your code. Laugh | :laugh:

So, either use the sw stream to write to the file, or get rid of it completely, and just use the File.AppendAllText method instead - but don't try to use both.

And if you do go with your own stream (which in this case is probably a good idea as you only open and lock the file once) remember to Close and Dispose the stream when you have finished - or the next time you call that code the file will still be locked from the first time!

Those who fail to learn history are doomed to repeat it. --- George Santayana (December 16, 1863 – September 26, 1952)
Those who fail to clear history are doomed to explain it. --- OriginalGriff (February 24, 1959 – ∞)

Re: writing to a file while Looping

Kasun Liyanage30-Apr-14 8:31

Kasun Liyanage

30-Apr-14 8:31

Hey thanks man Smile | :)

learned some stuff from that. And it worked :v

Later

Re: writing to a file while Looping

OriginalGriff30-Apr-14 8:39

OriginalGriff

30-Apr-14 8:39

You're welcome!

Power point file formatter

Taimoor Hassun29-Apr-14 18:21

29-Apr-14 18:21

Hi..!
i want to make an application in C #
that will standardized .ppt and .pptx files.
now i want to extract the text in files
and check following properties.
font style, font size,heading and sub heading style and size, number of bullets in each slide etc..
Can anyone help to do the following things in C Sharp..
please share your ideas and experience related to this with me.
All of you are warmly welcome..
Thankssss in advance....

Richard MacCutchan29-Apr-14 20:26

Richard MacCutchan

29-Apr-14 20:26

You need to use the Microsoft.Office.Interop.PowerPoint Namespace[^] to read the contents of these files. You may like to use Google to search for samples.

Taimoor Hassun29-Apr-14 21:00

29-Apr-14 21:00

thanks but how can i change the font size and style in a ppt file through C#.

Richard MacCutchan29-Apr-14 21:08

Richard MacCutchan

29-Apr-14 21:08

taimurhasan wrote:
how can i change the font size and style in a ppt file through C#.

You will have to find the appropriate calls in the interop as documented in the link I gave you.

Taimoor Hassun30-Apr-14 4:54

30-Apr-14 4:54

ok thanks i will try..

Chris Quinn30-Apr-14 4:57

Chris Quinn

30-Apr-14 4:57

If you know how to do it within Powerpoint, record your actions as a macro, then look at the generated code - this will give you big hints about what you need to do in C#, even though the code will be in VBA

=========================================================
I'm an optoholic - my glass is always half full of vodka.
=========================================================

Taimoor Hassun30-Apr-14 6:17

30-Apr-14 6:17

Sorry i can't understand what you want to say.. can u explain ??

help me

Member 1078417429-Apr-14 14:18

Member 10784174

29-Apr-14 14:18

Hi I'm brand new to this stuff and still grasping the concepts and terms associated with C#

I was looking through my C# book and came across this example project. It asked you to create a one-form application that will gather the following:

First Name
Last Name
Address
City
State
Zip
Telephone

You must include the following features:

The form must start in the center of the screen.
You must have a nice title for your form.
There must be an END button that stops your program.
You need another button that will display a message box when they click it. The message needs to say "Thanks for shopping [Name]".
All the fonts/colors/alignments must look clean and orderly.

I know to an experienced C# programmer, this kind of stuff is second nature. I'm looking for anyone who could help me out with any infomation so I can understand this a little more (since the book didn't show how to do it!) Thanks!

Peter Leow29-Apr-14 14:36

Peter Leow

29-Apr-14 14:36

I thought your book would have taught you all these basic stuff. If not, dump the book and switch to
Create a Windows Forms Application Project[^]

OriginalGriff29-Apr-14 20:10

OriginalGriff

29-Apr-14 20:10

Member 10784174 wrote:
the book didn't show how to do it!

Your book probably does show how to do it, but it won't spell it out for you - part of learning development is learning to think about the problem and work out a solution - it expects you to apply what it has told you, not blindly regurgitate it (unlike most school work).

If you can't work out what it means in one go, then do each bit separately: first, center the form. Then change the title. And so forth. Doing it that way, it's a very simple task, honest! Laugh | :laugh:

If you don't think the book has explained what you need to do, then there are two possibilities:
1) It's a rubbish book. Check the title: does it have "for Dummies", multiple exclamation marks, or "in xxx days" in it? If it does, then it's almost certainly rubbish. If it doesn't, it's probably ok.
2) You aren't reading the book, just skipping through and trying one of the exercises without trying to understand the material in the chapter(s) before it.

The solution to the first is simple: get a better book. Anything by Addison-Wesley, or Wrox is probably fine.
But I suspect you need the second solution: Go back to page one, and start reading from there. And do the exercises in order as you meet them!

Rob Philpott30-Apr-14 2:17

Rob Philpott

30-Apr-14 2:17

Interesting book that only asks you to do stuff without explaining it first. What is the title?

Regards,
Rob Philpott.

Pete O'Hanlon30-Apr-14 6:35

Pete O'Hanlon

30-Apr-14 6:35

I bet it's something like Learn C# in 24 Hours.