Re: C# Windows Service - C# Discussion Boards

Hi all,

Thanks very much for the suggestions so far. Will implement those changes now, hopefully that will sort this last bug out.

Much obliged to you all,

Scott

Hi,

as others already explained, FSW has a limited buffer, so for a very active folder you might miss some events, however that seldom is the problem; the actual problem typically is FSW gets triggered by the beginning of some action (such as file creation), whereas your app typically is interested in the end of the action (file created and available).

My solution (applies only if the producer can be slightly changed) is by using a sentinel file: have the producer create and write the file of interest first, then emit a small file that signals the former has been created and written; and now make the FSW watch out for that sentinel file only; it being small causes start and end creation to coincide, so there is no need to wait or to retry. And you could store the data file's name inside the sentinel file, to remove all uncertainty.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

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Sorry Luc for being lazy but would this still be an issue when streaming data in a separate thread?

"You get that on the big jobs."

Hi Rob, I have no idea what you are asking here.

FWIW: the FSW events get handled in a ThreadPool thread. They fire upon filesystem events such as create file, write to file, delete file, which all indicate the start of an action. There is no event for flushing or closing a file.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

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modified on Friday, June 10, 2011 8:38 PM

OK, I was just thinking one of the main reasons the FSW InternalBuffer would overflow is because the code block within the subscribing method is taking time (ie reading file) and so other events are backing up in the buffer. And maybe a better way would be to thread the reading of the file into a separate thread to help avoid the InternalBuffer overflowing.

I guess it still isn't a solution to the problem anyway, just a way to help minimise it.

"You get that on the big jobs."

Oh, I see, yes when a consumer temporarily can not keep up with a producer, you would need more buffering, or split the consumption effort in a real-time task and a delayed task (a queue could be helpful here).

Under the same conditions, and assuming new files (OnCreate) are of interest, it might be wise not to use a FSW at all, and to scan the folder yourself (e.g.with Directory.GetFiles or the newer Directory.EnumerateFiles) especially if the consumer is to also delete the files once processed.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

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Good idea. I suppose whatever is writing the file could also write it to a different folder and then perform a move operation to move it to the monitored folder once the file is fully written.

[Managing Your JavaScript Library in ASP.NET]

That would work too, however I'm not fond of moving or renaming files (unless that is exactly what is wanted) as there are too many side-effects.

One example is MS Word editing a doc file on the desktop; it renames the old file resulting in a weird filename on the desktop, and creates a new one, in an "arbitrary" location, also on the desktop of course; when done, the old is removed, the new one renamed to its original name, not its original location.

And then there is the single responsibility idea, see SOLID. One file holding content, one file signaling new information!

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Luc Pattyn [My Articles] Nil Volentibus Arduum

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Well, I think the SRP refers more to the functionality than the data being operated on (the files, in this case). You could have one bit of functionality that creates the file, then another to move the file (or rename it).

Now that I think about it, I'd probably go with the rename option (from a practical perspective). Less clutter IMO (no need to keep track of a second folder, and no extra file to clean up).

[Managing Your JavaScript Library in ASP.NET]

With renaming, you're potentially in for a surprise. You have to close the file before you can rename it, and in that short period of time the file could be opened by any of those utterly helpful little programs (indexers, virus scanners, etc) trying to inspect or process the new information, and thus preventing you from renaming the file. So you end up creating the same wait-and-retry loop you need to get reasonable chance of deleting a newly created file; and this logic needs to be added to the producer, who wouldn't really care much. That is why I prefer the sentinel file scheme.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

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Hi guys

i wanna get url from navigators like ie, firefox nd opera. but when i run the navigator after my application, i get this exception "CallbackOnCollectedDelegate" xD
here's my code

[DllImport("USER32.DLL", EntryPoint = "DdeClientTransaction",
            CharSet = CharSet.Unicode, ExactSpelling = true,
            CallingConvention = CallingConvention.StdCall)]//here
        private static extern IntPtr DdeClientTransaction(byte[] pData, uint cbData,
            IntPtr hConv, IntPtr hszItem, ClipboardFormat wFmt, XTYP wType, uint dwTimeout, ref uint pdwResult);
   

public static byte[] Request(string item, ClipboardFormat wFormat)
        {
            try
            {
                if (hConv == IntPtr.Zero)
                    return null;

                // Création de la chaîne DDE de l'élément.
                IntPtr hszItem = DdeCreateStringHandle(DDEid, item, CP_UNICODE);
                if ((hszItem == IntPtr.Zero) && (item.Length != 0))
                    return null;
                // Exécution de la transaction.
                uint res = 0;
                IntPtr data = DdeClientTransaction(null, 0, hConv, hszItem, wFormat, XTYP.REQUEST, timeout, ref res);  // i get the problem here :'(
                // Libération de la chaîne DDE.
                if (hszItem != IntPtr.Zero)
                    DdeFreeStringHandle(DDEid, hszItem);
                // Récupération des données.
                if (data != IntPtr.Zero)
                {
                    uint len = DdeGetData(data, null, 0, 0);
                    byte[] buffer = new byte[len];
                    DdeGetData(data, buffer, len, 0);
                    return buffer;
                }
            }
            catch (NullReferenceException r)
            { System.Windows.Forms.MessageBox.Show(r.Message); }

in the main i call this method to get url like this

NavUrl _navigation = new NavUrl();
                            IntPtr hffconv = _navigation.Connect("IExplore", "WWW_GetWindowInfo", ref path);//pour IE
                            if (hffconv != IntPtr.Zero)
                            {

                                byte[] wwwFF = _navigation.Request("0xFFFFFFFF", NavUrl.ClipboardFormat.TEXT);
                                if (wwwFF != null)
                                {
                                    urls = System.Text.ASCIIEncoding.UTF7.GetString(wwwFF);
                                    _navigation.Disconnect();

                                    lastIe = urls;
                                    indexTitle = urls.IndexOf("\",\"");
                                    indexTitleEnd = urls.IndexOf("\"", indexTitle + 3);

thank u

Hi all, I need to format string and having some problems.
when user enter into a textbox i.e "12345678". I need to format
this input into this. "12 345 678". I am doing this way but not working

string p = TextBox.Text.Trim();
string.Format("{0},{1},{2}", p.Substring(0,2), p.Substring(2,4), p.Substring(5,7));

You should probably remove the comma's from your Format string. The rest is just about adding up your substring index and length values correctly.

Need custom software developed? I do custom programming based primarily on MS tools with an emphasis on C# development and consulting. I also do Android Programming as I find it a refreshing break from the MS.

"And they, since they Were not the one dead, turned to their affairs" -- Robert Frost

You should replace commas to spaces and String.Format is uppercase in the S

mabrahao wrote:
String.Format is uppercase in the S

Actually, both string and String will work.

[Managing Your JavaScript Library in ASP.NET]

Try this:

C#

string p = TextBox.Text.Trim();
p = string.Format("{0} {1} {2}", p.Substring(0, 2), p.Substring(2, 3), p.Substring(5, 3));
// If you are using Windows Forms, this will show the output. You will do it differently if you are using ASP.NET.
MessageBox.Show(p);

Here is what was wrong with your code:

Your sample output contains spaces, but your format strong contains commas.
string.Format returns the modified string, yet you were not assigning the return value to anything.
string.Substring has 2 parameters. The second prameter is the string length, not a second index. So where you used 4 and 7, you should have used 3.

[Managing Your JavaScript Library in ASP.NET]

Thanks for your reply. it is working for me.

One thing you should know - the second parameter in Substring is not the position to end on, it's the length of the substring to extract. It goes Substring(index, length);

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Repost.

[Managing Your JavaScript Library in ASP.NET]

You should NOT do this with string manipulations; it would go completely wrong if the user types strange things, such as the intended number prefixed with a lot of zeroes.

The proper way to do this consists of two steps:

1.
parse the user input, i.e. turn his characters into an actual number. The simplest way would be:

int val;
bool OK=int.TryParse(myTextBox.Text, out val);

Whatever the user does wrong (e.g. typing letters, or providing no input at all) will result in OK being false; if the input is acceptable, OK will be true and val will contain its value.

2.
format the number in the way you want it. A simple way to get two spaces in a number assumed to require 8 digits is:

string s=string.Format("{0:## ### ###.##}", val);

Assuming val=12345678 the result will be 12 345 678

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

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I always like your answers.

Could be also
1. If the currect culture uses ' ' as a group separator:

string.Format("{0:n0}", val)

2. If it doesn't:

var provider = (CultureInfo) CultureInfo.CurrentCulture.Clone();
provider.NumberFormat.NumberGroupSeparator = " ";
string.Format(provider, "{0:n0}", val);

Greetings - Jacek

yes, there are alternatives for each of both steps. Having the two steps was the essence in my message.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

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To be precise: My (1) and (2) were alternatives to your (2). They both assumes that your (1) was already done.

Greetings - Jacek

Of course; and that is how I understood it.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

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