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FileSystemWatcher raises Changed Twice....Has anyone else noticed that the FileSystemWatcher raises the changed event
twice when a file is changed? Do you have any idea why this is the case? This has been asked several times before:
http://groups.google.com/groups?lnk=hpsg&hl=en&q=FileSystemWatcher+twice Show quoteHide quote "ljh" <Reply@groups.please> wrote in message news:cMEkg.9108$y%3.8407@bignews1.bellsouth.net... > Has anyone else noticed that the FileSystemWatcher raises the changed > event twice when a file is changed? > > Do you have any idea why this is the case? > > > I saw those.....but there is no real solution listed there.
This seems to be another of .Nets gotcha's. Something that sounds great, but doesn't really work out in real world programming. The scary part for me is not the redundant changed messages so much as the possibility of missing events. Microsoft's documentation says "The Windows operating system notifies your component of file changes in a buffer created by the FileSystemWatcher. If there are many changes in a short time, the buffer can overflow. This causes the component to lose track of changes in the directory, and it will only provide blanket notification. Increasing the size of the buffer with the InternalBufferSize property is expensive, as it comes from non-paged memory that cannot be swapped out to disk, so keep the buffer as small yet large enough to not miss any file change events. To avoid a buffer overflow, use the NotifyFilter and IncludeSubdirectories properties so you can filter out unwanted change notifications. " (http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher(d=ide).aspx) So changes can happen, as with the moving of a directory with many files and/or subdirectories, that you may miss if your InternalBufferSize is not set high enough. I say set it higher than you may need. After all, what is more "expensive" than an app that does not perform as advertised? Show quoteHide quote "Lebesgue" <lebes***@gmail.com> wrote in message news:uYsIkbYkGHA.324@TK2MSFTNGP02.phx.gbl... > This has been asked several times before: > http://groups.google.com/groups?lnk=hpsg&hl=en&q=FileSystemWatcher+twice > > "ljh" <Reply@groups.please> wrote in message > news:cMEkg.9108$y%3.8407@bignews1.bellsouth.net... >> Has anyone else noticed that the FileSystemWatcher raises the changed >> event twice when a file is changed? >> >> Do you have any idea why this is the case? >> >> >> > > For more info on the InternalBufferSize property go to
http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher.internalbuffersize(d=ide).aspx. Show quoteHide quote "ljh" <Reply@groups.please> wrote in message news:qvFkg.9126$y%3.1516@bignews1.bellsouth.net... >I saw those.....but there is no real solution listed there. > > This seems to be another of .Nets gotcha's. Something that sounds great, > but doesn't really work out in real world programming. > > The scary part for me is not the redundant changed messages so much as the > possibility of missing events. Microsoft's documentation says "The > Windows operating system notifies your component of file changes in a > buffer created by the FileSystemWatcher. If there are many changes in a > short time, the buffer can overflow. This causes the component to lose > track of changes in the directory, and it will only provide blanket > notification. Increasing the size of the buffer with the > InternalBufferSize property is expensive, as it comes from non-paged > memory that cannot be swapped out to disk, so keep the buffer as small yet > large enough to not miss any file change events. To avoid a buffer > overflow, use the NotifyFilter and IncludeSubdirectories properties so you > can filter out unwanted change notifications. " > (http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher(d=ide).aspx) > > So changes can happen, as with the moving of a directory with many files > and/or subdirectories, that you may miss if your InternalBufferSize is not > set high enough. I say set it higher than you may need. After all, what > is more "expensive" than an app that does not perform as advertised? > > > "Lebesgue" <lebes***@gmail.com> wrote in message > news:uYsIkbYkGHA.324@TK2MSFTNGP02.phx.gbl... >> This has been asked several times before: >> http://groups.google.com/groups?lnk=hpsg&hl=en&q=FileSystemWatcher+twice >> >> "ljh" <Reply@groups.please> wrote in message >> news:cMEkg.9108$y%3.8407@bignews1.bellsouth.net... >>> Has anyone else noticed that the FileSystemWatcher raises the changed >>> event twice when a file is changed? >>> >>> Do you have any idea why this is the case? >>> >>> >>> >> >> > > Well, it seems that using an integer-sized value (directly or via a
declared integer variable) will NOT let you (or at least me) increase the size of the InternalBufferSize value in a FileSystemWatcher object. Whenever I use a statement like "FileSystemWatcher1.InternalBufferSize = 12288" I get an error message that says "The path is not of a legal form." with a link (http://msdn2.microsoft.com/en-us/library/ms242197(VS.80,d=ide).aspx) to a page that describes the error as "The exception that is thrown when one of the arguments provided to a method is not valid." This seems to be in direct contradiction to the sample code posted at (http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher.internalbuffersize(d=ide).aspx) that states that you can use an integer to set the property to a multiple of 4096. Am I just doing something stupid here? Show quoteHide quote "ljh" <Reply@groups.please> wrote in message news:gxFkg.9128$y%3.4976@bignews1.bellsouth.net... > For more info on the InternalBufferSize property go to > http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher.internalbuffersize(d=ide).aspx. > > > > "ljh" <Reply@groups.please> wrote in message > news:qvFkg.9126$y%3.1516@bignews1.bellsouth.net... >>I saw those.....but there is no real solution listed there. >> >> This seems to be another of .Nets gotcha's. Something that sounds great, >> but doesn't really work out in real world programming. >> >> The scary part for me is not the redundant changed messages so much as >> the possibility of missing events. Microsoft's documentation says "The >> Windows operating system notifies your component of file changes in a >> buffer created by the FileSystemWatcher. If there are many changes in a >> short time, the buffer can overflow. This causes the component to lose >> track of changes in the directory, and it will only provide blanket >> notification. Increasing the size of the buffer with the >> InternalBufferSize property is expensive, as it comes from non-paged >> memory that cannot be swapped out to disk, so keep the buffer as small >> yet large enough to not miss any file change events. To avoid a buffer >> overflow, use the NotifyFilter and IncludeSubdirectories properties so >> you can filter out unwanted change notifications. " >> (http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher(d=ide).aspx) >> >> So changes can happen, as with the moving of a directory with many files >> and/or subdirectories, that you may miss if your InternalBufferSize is >> not set high enough. I say set it higher than you may need. After all, >> what is more "expensive" than an app that does not perform as advertised? >> >> >> "Lebesgue" <lebes***@gmail.com> wrote in message >> news:uYsIkbYkGHA.324@TK2MSFTNGP02.phx.gbl... >>> This has been asked several times before: >>> http://groups.google.com/groups?lnk=hpsg&hl=en&q=FileSystemWatcher+twice >>> >>> "ljh" <Reply@groups.please> wrote in message >>> news:cMEkg.9108$y%3.8407@bignews1.bellsouth.net... >>>> Has anyone else noticed that the FileSystemWatcher raises the changed >>>> event twice when a file is changed? >>>> >>>> Do you have any idea why this is the case? >>>> >>>> >>>> >>> >>> >> >> > > The GOTCHA here seems to be that you MUST set the PATH property before you
can set/change the InternalBuffer property. Don't ask me why...... Show quoteHide quote "ljh" <Reply@groups.please> wrote in message news:wTFkg.9130$y%3.5666@bignews1.bellsouth.net... > Well, it seems that using an integer-sized value (directly or via a > declared integer variable) will NOT let you (or at least me) increase the > size of the InternalBufferSize value in a FileSystemWatcher object. > > Whenever I use a statement like "FileSystemWatcher1.InternalBufferSize = > 12288" I get an error message that says "The path is not of a legal > form." with a link > (http://msdn2.microsoft.com/en-us/library/ms242197(VS.80,d=ide).aspx) to a > page that describes the error as "The exception that is thrown when one of > the arguments provided to a method is not valid." > > This seems to be in direct contradiction to the sample code posted at > (http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher.internalbuffersize(d=ide).aspx) > that states that you can use an integer to set the property to a multiple > of 4096. > > Am I just doing something stupid here? > > > > "ljh" <Reply@groups.please> wrote in message > news:gxFkg.9128$y%3.4976@bignews1.bellsouth.net... >> For more info on the InternalBufferSize property go to >> http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher.internalbuffersize(d=ide).aspx. >> >> >> >> "ljh" <Reply@groups.please> wrote in message >> news:qvFkg.9126$y%3.1516@bignews1.bellsouth.net... >>>I saw those.....but there is no real solution listed there. >>> >>> This seems to be another of .Nets gotcha's. Something that sounds >>> great, but doesn't really work out in real world programming. >>> >>> The scary part for me is not the redundant changed messages so much as >>> the possibility of missing events. Microsoft's documentation says "The >>> Windows operating system notifies your component of file changes in a >>> buffer created by the FileSystemWatcher. If there are many changes in a >>> short time, the buffer can overflow. This causes the component to lose >>> track of changes in the directory, and it will only provide blanket >>> notification. Increasing the size of the buffer with the >>> InternalBufferSize property is expensive, as it comes from non-paged >>> memory that cannot be swapped out to disk, so keep the buffer as small >>> yet large enough to not miss any file change events. To avoid a buffer >>> overflow, use the NotifyFilter and IncludeSubdirectories properties so >>> you can filter out unwanted change notifications. " >>> (http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher(d=ide).aspx) >>> >>> So changes can happen, as with the moving of a directory with many files >>> and/or subdirectories, that you may miss if your InternalBufferSize is >>> not set high enough. I say set it higher than you may need. After all, >>> what is more "expensive" than an app that does not perform as >>> advertised? >>> >>> >>> "Lebesgue" <lebes***@gmail.com> wrote in message >>> news:uYsIkbYkGHA.324@TK2MSFTNGP02.phx.gbl... >>>> This has been asked several times before: >>>> http://groups.google.com/groups?lnk=hpsg&hl=en&q=FileSystemWatcher+twice >>>> >>>> "ljh" <Reply@groups.please> wrote in message >>>> news:cMEkg.9108$y%3.8407@bignews1.bellsouth.net... >>>>> Has anyone else noticed that the FileSystemWatcher raises the changed >>>>> event twice when a file is changed? >>>>> >>>>> Do you have any idea why this is the case? >>>>> >>>>> >>>>> >>>> >>>> >>> >>> >> >> > > If you use "*.doc" for the filter in your FileSystemWatcher control, you
will also recieve events for *.tmp files created and destroyed by Word. Not really sure why.... Show quoteHide quote "ljh" <Reply@groups.please> wrote in message news:HYFkg.9131$y%3.8962@bignews1.bellsouth.net... > The GOTCHA here seems to be that you MUST set the PATH property before you > can set/change the InternalBuffer property. > > Don't ask me why...... > > "ljh" <Reply@groups.please> wrote in message > news:wTFkg.9130$y%3.5666@bignews1.bellsouth.net... >> Well, it seems that using an integer-sized value (directly or via a >> declared integer variable) will NOT let you (or at least me) increase the >> size of the InternalBufferSize value in a FileSystemWatcher object. >> >> Whenever I use a statement like "FileSystemWatcher1.InternalBufferSize = >> 12288" I get an error message that says "The path is not of a legal >> form." with a link >> (http://msdn2.microsoft.com/en-us/library/ms242197(VS.80,d=ide).aspx) to >> a page that describes the error as "The exception that is thrown when one >> of the arguments provided to a method is not valid." >> >> This seems to be in direct contradiction to the sample code posted at >> (http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher.internalbuffersize(d=ide).aspx) >> that states that you can use an integer to set the property to a multiple >> of 4096. >> >> Am I just doing something stupid here? >> >> >> >> "ljh" <Reply@groups.please> wrote in message >> news:gxFkg.9128$y%3.4976@bignews1.bellsouth.net... >>> For more info on the InternalBufferSize property go to >>> http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher.internalbuffersize(d=ide).aspx. >>> >>> >>> >>> "ljh" <Reply@groups.please> wrote in message >>> news:qvFkg.9126$y%3.1516@bignews1.bellsouth.net... >>>>I saw those.....but there is no real solution listed there. >>>> >>>> This seems to be another of .Nets gotcha's. Something that sounds >>>> great, but doesn't really work out in real world programming. >>>> >>>> The scary part for me is not the redundant changed messages so much as >>>> the possibility of missing events. Microsoft's documentation says "The >>>> Windows operating system notifies your component of file changes in a >>>> buffer created by the FileSystemWatcher. If there are many changes in a >>>> short time, the buffer can overflow. This causes the component to lose >>>> track of changes in the directory, and it will only provide blanket >>>> notification. Increasing the size of the buffer with the >>>> InternalBufferSize property is expensive, as it comes from non-paged >>>> memory that cannot be swapped out to disk, so keep the buffer as small >>>> yet large enough to not miss any file change events. To avoid a buffer >>>> overflow, use the NotifyFilter and IncludeSubdirectories properties so >>>> you can filter out unwanted change notifications. " >>>> (http://msdn2.microsoft.com/en-us/library/system.io.filesystemwatcher(d=ide).aspx) >>>> >>>> So changes can happen, as with the moving of a directory with many >>>> files and/or subdirectories, that you may miss if your >>>> InternalBufferSize is not set high enough. I say set it higher than >>>> you may need. After all, what is more "expensive" than an app that >>>> does not perform as advertised? >>>> >>>> >>>> "Lebesgue" <lebes***@gmail.com> wrote in message >>>> news:uYsIkbYkGHA.324@TK2MSFTNGP02.phx.gbl... >>>>> This has been asked several times before: >>>>> http://groups.google.com/groups?lnk=hpsg&hl=en&q=FileSystemWatcher+twice >>>>> >>>>> "ljh" <Reply@groups.please> wrote in message >>>>> news:cMEkg.9108$y%3.8407@bignews1.bellsouth.net... >>>>>> Has anyone else noticed that the FileSystemWatcher raises the changed >>>>>> event twice when a file is changed? >>>>>> >>>>>> Do you have any idea why this is the case? >>>>>> >>>>>> >>>>>> >>>>> >>>>> >>>> >>>> >>> >>> >> >> > > "ljh" <Reply@groups.please> wrote in message This has nothing to do with .NET, it's the way the FS signals events to the news:qvFkg.9126$y%3.1516@bignews1.bellsouth.net... |I saw those.....but there is no real solution listed there. | | This seems to be another of .Nets gotcha's. Something that sounds great, | but doesn't really work out in real world programming. | OS and the way the FileSystemWatcher's underlying Win32 API (ReadDirectoryChangesW) presents FS event info to the caller. If you really want to know how FSW works check ReadDirectoryChangesW in MSDN. Willy.
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"Willy Denoyette [MVP]" <willy.denoye***@telenet.be> wrote in message That's why I'd much rather be able to detect running instances of Word and news:%23nsx4mZkGHA.4104@TK2MSFTNGP04.phx.gbl... > > "ljh" <Reply@groups.please> wrote in message > news:qvFkg.9126$y%3.1516@bignews1.bellsouth.net... > |I saw those.....but there is no real solution listed there. > | > | This seems to be another of .Nets gotcha's. Something that sounds > great, > | but doesn't really work out in real world programming. > | > > This has nothing to do with .NET, it's the way the FS signals events to > the > OS and the way the FileSystemWatcher's underlying Win32 API > (ReadDirectoryChangesW) presents FS event info to the caller. trap events like the saving of a file. Alas, that does not seem to be possible with .Net. I have seen tons of code that show how to create an instance of Word (or Excel or Access or Outlook) and manipulate it programatically, but not one that can show how to detect a running instance of Word and basically watch what the user is doing with the files. I am almost certain that this is not possible with managed code at all. Another capability wiped out in the name of "safe" code. Although, I suppose it has to be that way. If Microsoft really seeks to save people (programmers) from themselves (which is a fool's game in any industry), they have to take away the tools that they mis-use to do so. You can't have "safe" and all-powerful in the same toolset. IMHO, it looks like we're sacrificing power for "safety" with .Net. Not a decision I would have made......but..........
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"ljh" <Reply@groups.please> wrote in message I said that FileSystemWatcher uses the underlying Win32 API news:dSIkg.9158$y%3.3090@bignews1.bellsouth.net... | | "Willy Denoyette [MVP]" <willy.denoye***@telenet.be> wrote in message | news:%23nsx4mZkGHA.4104@TK2MSFTNGP04.phx.gbl... | > | > "ljh" <Reply@groups.please> wrote in message | > news:qvFkg.9126$y%3.1516@bignews1.bellsouth.net... | > |I saw those.....but there is no real solution listed there. | > | | > | This seems to be another of .Nets gotcha's. Something that sounds | > great, | > | but doesn't really work out in real world programming. | > | | > | > This has nothing to do with .NET, it's the way the FS signals events to | > the | > OS and the way the FileSystemWatcher's underlying Win32 API | > (ReadDirectoryChangesW) presents FS event info to the caller. | | That's why I'd much rather be able to detect running instances of Word and | trap events like the saving of a file. Alas, that does not seem to be | possible with .Net. | | I have seen tons of code that show how to create an instance of Word (or | Excel or Access or Outlook) and manipulate it programatically, but not one | that can show how to detect a running instance of Word and basically watch | what the user is doing with the files. | | I am almost certain that this is not possible with managed code at all. | Another capability wiped out in the name of "safe" code. | "ReadDirectoryChangesW", even if you use native code in you scenario you will see two change events, Also ReadDirectoryChangesW is an API designed to watch "Directory" changes not File changes, so is FSW. The reason why see two events is because when Word saves a document, it first save the old contents of the doc .file into a .tmp file (a rename), after which he copies the new document contents into a .tmp file and renames this .tmp back into your .doc file (a rename again). Another thing to keep in mind is that Word maintains a lock file in the same directory as the .doc file, this lock file has the same name as the .doc file with ~$ prepended. This file is created and changed when words opens a doc file, it 'deletes'this lock file when the .doc file gets closed. So it's just a matter of carefully selecting your NotifyFilters, and have an idea about what exactly is done by the applicatins accesing the files in the watched directory. | Although, I suppose it has to be that way. If Microsoft really seeks to Again, .NET has nothing to do with this, but if you don't believe it, no one | save people (programmers) from themselves (which is a fool's game in any | industry), they have to take away the tools that they mis-use to do so. | | You can't have "safe" and all-powerful in the same toolset. IMHO, it looks | like we're sacrificing power for "safety" with .Net. | stops you do it in native code. Willy.
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"Willy Denoyette [MVP]" <willy.denoye***@telenet.be> wrote in message I understand what you are saying. The problem is that different systems may news:eQk%23PGikGHA.4884@TK2MSFTNGP03.phx.gbl... > > > > > "ljh" <Reply@groups.please> wrote in message > news:dSIkg.9158$y%3.3090@bignews1.bellsouth.net... > | > | "Willy Denoyette [MVP]" <willy.denoye***@telenet.be> wrote in message > | news:%23nsx4mZkGHA.4104@TK2MSFTNGP04.phx.gbl... > | > > | > "ljh" <Reply@groups.please> wrote in message > | > news:qvFkg.9126$y%3.1516@bignews1.bellsouth.net... > | > |I saw those.....but there is no real solution listed there. > | > | > | > | This seems to be another of .Nets gotcha's. Something that sounds > | > great, > | > | but doesn't really work out in real world programming. > | > | > | > > | > This has nothing to do with .NET, it's the way the FS signals events > to > | > the > | > OS and the way the FileSystemWatcher's underlying Win32 API > | > (ReadDirectoryChangesW) presents FS event info to the caller. > | > | That's why I'd much rather be able to detect running instances of Word > and > | trap events like the saving of a file. Alas, that does not seem to be > | possible with .Net. > | > | I have seen tons of code that show how to create an instance of Word (or > | Excel or Access or Outlook) and manipulate it programatically, but not > one > | that can show how to detect a running instance of Word and basically > watch > | what the user is doing with the files. > | > | I am almost certain that this is not possible with managed code at all. > | Another capability wiped out in the name of "safe" code. > | > > I said that FileSystemWatcher uses the underlying Win32 API > "ReadDirectoryChangesW", even if you use native code in you scenario you > will see two change events, Also ReadDirectoryChangesW is an API designed > to > watch "Directory" changes not File changes, so is FSW. > > The reason why see two events is because when Word saves a document, it > first save the old contents of the doc .file into a .tmp file (a rename), > after which he copies the new document contents into a .tmp file and > renames > this .tmp back into your .doc file (a rename again). Another thing to keep > in mind is that Word maintains a lock file in the same directory as the > .doc > file, this lock file has the same name as the .doc file with ~$ prepended. > This file is created and changed when words opens a doc file, it > 'deletes'this lock file when the .doc file gets closed. So it's just a > matter of carefully selecting your NotifyFilters, and have an idea about > what exactly is done by the applicatins accesing the files in the watched > directory. > raise different events in different orders depending upon what applications on the systems (i.e. real time antivirus, antispyware, defraggers, etc.) are accessing the files. It is quite impossible (at least for me) to be able to take every scenario and combination of software into consideration to determine exactly what has transpired when a FS event is fired on any system. What is needed in FileSystemWatcher (IMHO) is the ability to know which process or exe is executing the FS function. This way, we could not only filter on specific files, but also on specific programs that deal with those files. For example, you could filter with "*.doc" and "winword.exe". Then, if Word did anything to a DOC file, you'd know - without all of the potentially confusing FS events that may be fired by God-only-knows-what programs. > | Although, I suppose it has to be that way. If Microsoft really seeks to I will need to do COM interop to bring in old code to accomplish part of the > | save people (programmers) from themselves (which is a fool's game in any > | industry), they have to take away the tools that they mis-use to do so. > | > | You can't have "safe" and all-powerful in the same toolset. IMHO, it > looks > | like we're sacrificing power for "safety" with .Net. > | > > Again, .NET has nothing to do with this, but if you don't believe it, no > one > stops you do it in native code. functionality that is not (as far as I can see) possible with .Net. I may be missing something, but I do not see the ability in .Net to monitor system-wide keystrokes or mouse events. Did I miss it somewhere? Thanks for your response! > I will need to do COM interop to bring in old code to accomplish part of You can do a limited set of system hooks including keyboard and mouse events > the > functionality that is not (as far as I can see) possible with .Net. I may > be missing something, but I do not see the ability in .Net to monitor > system-wide keystrokes or mouse events. Did I miss it somewhere? > > Thanks for your response! > > in .NET see: http://www.codeproject.com/csharp/GlobalSystemHook.asp?msg=840940 Thanks for the link Lebesgue!
Show quoteHide quote "Lebesgue" <lebes***@gmail.com> wrote in message news:Oa%23XEqlkGHA.896@TK2MSFTNGP04.phx.gbl... > >> I will need to do COM interop to bring in old code to accomplish part of >> the >> functionality that is not (as far as I can see) possible with .Net. I >> may be missing something, but I do not see the ability in .Net to monitor >> system-wide keystrokes or mouse events. Did I miss it somewhere? >> >> Thanks for your response! >> >> > > You can do a limited set of system hooks including keyboard and mouse > events in .NET see: > http://www.codeproject.com/csharp/GlobalSystemHook.asp?msg=840940 > 
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