I wrote an Async method in C# to write to a file, however I keep on getting the following exception:
The process cannot access the file
'C:\XXX\XXX\XXX\XXX\EventBuffer.txt' because it is being used by
another process.
I've had a look at similar questions already posted on SO such as this one, and this one but it seems like the cause of my issue is different.
I used a process monitor to see which processes are trying to access the directory in which the file is in but the only process trying to access it is the one I'm debugging (Will post a snippet soon of the debug process window).
It isn't that file access was being attempted before it was closed upon last access, because I can get the exception when I attempt to access the file for the first time. I have tried to implement a delay after the StreamWriter is instantiated incase the write method was being attempted, I wasn't using the using block before and was disposing of the object using it's dispose methods but in one of the similar questions a this solved the issue.
public static async void UpdateEventBufferFile(EventDetails EventDtls)
{
string line;
try
{
using (StreamWriter EventBufferFile = new StreamWriter(FilePath, true)) // creates the file
{
//All barcode data space sperated for split detection
line = EventDtls.SiteID + " " + EventDtls.McID + " " + EventDtls.EventID + " "
+ EventDtls.EventDT + " " + EventDtls.AdditionalInfo;
await Task.Run(() => LogFileManager.SystematicLog(" Events " + line + " added to buffer file", " BufferFileWriter.cs"));
await EventBufferFile.WriteLineAsync(line); //no need for new line char WriteLine does that
await EventBufferFile.FlushAsync();
//The using block is suffice to dispose of the object the below is no longer required
//EventBufferFile.Dispose();
//EventBufferFile.Close();
//EventBufferFile = null;
}
}
catch (Exception ex)
{
}
}
I have near identical methods utilised within other classes that don't cause the same issue, which annoys me quite a bit.
The method is not being invoked from within a Loop. Invocation is done in a seprate static class in the method below:
public static void AddCentralEvents(int SiteID, int McID, int EventID, DateTime EventDT, string AdditionalInfo)
{
EventDetails EventDetailsObj = new EventDetails();
EventDetailsObj.SiteID = SiteID;
EventDetailsObj.McID = McID;
EventDetailsObj.EventID = EventID;
EventDetailsObj.EventDT = EventDT;
EventDetailsObj.AdditionalInfo = AdditionalInfo;
Task.Run(() => BufferFileWriter.UpdateEventBufferFile(EventDetailsObj));
}
The error is self explanatory, you are using an ASYNC method (in a loop perhaps) and while your first task hasn't completed it's run (i.e. written to the file) that's why you are ending up with that error.
Have you tried writing with a synchronized method? If you have a requirement to periodically write to a file (i.e. logging) use a logging framework.
I recommend using log4net It is 'one of the' the best out there.
Related
This question already has answers here:
VS2010 does not show unhandled exception message in a WinForms Application on a 64-bit version of Windows
(5 answers)
Closed 9 years ago.
I am trying to save GetDirectories as a txt file, but somewhere my program fails.
private void Form1_Load(object sender, EventArgs e)
{
var directoryInfo = new System.IO.DirectoryInfo(#"g:\FTP\");
int directoryCount = directoryInfo.GetDirectories().Length;
...
var directoryInfo11 = new System.IO.DirectoryInfo(#"q:\FTP\");
int directoryCount11 = directoryInfo11.GetDirectories().Length;
int directoryCountMain = directoryCount + directoryCount2 +
directoryCount3 + directoryCount4 + directoryCount5 +
directoryCount6 + directoryCount7 + directoryCount8 +
directoryCount9 + directoryCount10 + directoryCount11;
string text = "Total Releases: ";
// WriteAllText creates a file, writes the specified string to the
// file, and then closes the file.
System.IO.File.WriteAllText(#"c:\test\ik.txt", text + directoryCountMain);
}
I don't get an error or anything, It looks like my code is skipped as I tried placing a MessageBox.Show below the code but It got ignored.
This won't solve your problem, but at least will shorten your code and make it maintainable. Replace your code with following, it will do the same.
var ftpDirs = new string[] { "g:/FTP/", ... };
int subDirsCount = 0;
foreach(var dir in ftpDirs)
{
subDirsCount += new DirectoryInfo(dir).GetDirectories().Length;
}
string text = "Total Releases: ";
File.WriteAllText(#"c:\test\ik.txt", string.Format("{0}{1}", text, subDirsCount));
Do not forget to add following at the top of the file.
using System.IO;
Place a breakpoint on the first statement in Form1_Load and see if it gets hit. If not, you probably need to subscribe to this event in your code.
If it gets hit, step through your code and find the line where it fails.
Note that Form_Load does not catch exceptions by default, so it will appear as though other lines were skipped. There are ways to solve it, just follow the above link.
I think this directories and path you have given doesnt exists or wrong therefore throwing exception when trying to get info
var directoryInfo11 = new System.IO.DirectoryInfo(#"q:\FTP\");
Add try catch block around your code and see if its throwing excpetion.
I am writing to a file, that is created for each date of the year, through code below. This code runs whenever, an unhandled exception occurs in an ASP.Net app. My problem is when many users are using the website, then this code could be hit due to several errors occurring at the same time, which could result in multiple requests to create or write to same file. What is the solution in this case so only one request executes the code related to writing to a file?
private void Application_Error(object sender, EventArgs e)
{
// Code that runs when an unhandled error occurs
string errorGuid = Guid.NewGuid().ToString("D");
if (HttpContext.Current.Server.GetLastError() != null)
{
Exception err = HttpContext.Current.Server.GetLastError();
string header = String.Format("/*****\t\t{0}:{1}\t\t*****/", "Start", errorGuid);
string footer = String.Format("/*****\t\t{0}:{1}\t\t*****/", "End", errorGuid);
string errorText = String.Format("{0}{5}Exception DateTime: {1}{5}Reference #: {2}{5}Exception:{5}=========={5}{3}{5}{4}{5}", header, System.DateTime.Now, errorGuid, err.ToString(), footer, Environment.NewLine);
// '~/ErrorReports/Logs/ErrorLog.log' must exist, else we will get an error
using (System.IO.TextWriter write = new System.IO.StreamWriter(HttpContext.Current.Server.MapPath("~/ErrorReports/Logs/ErrorLog_" + DateTime.Now.ToShortDateString() + ".log"), true, System.Text.Encoding.UTF8))
{
write.WriteLine(errorText);
write.Close();
}
}
}
1 - you can use the singleton pattern and create a class that will handle this file creation/append or
2 - use "lock"
3 - as suggested, use elmah
The problem I am facing has as follows:
I have developed a portable class library to encapsulate a service connection. Inside this class library there is a Resources.resw file containing strings. These strings are called only by methods of the class library (for example to override ToString() methods).
As I said this is a portable class library. If I reference it as a dll, or even as a project inside another solution, it gets built and compiles correctly. Then I make a call using a method of this library within my application, say
ClientFacadeConnector connector = new ClientFacadeConnector();
ICollection<SearchResult> results = null;
string message = string.Empty;
if (maxResults != -1) //Search with max Results
{
try
{
if (!contextQuery.Trim().Equals(string.Empty))
{
results = await connector.GetConnected().SearchAsync(contextQuery, query, maxResults);
message = "Search with ContextQuery " + contextQuery + ", Query " + query + ", max results " + maxResults.ToString();
}
else
{
results = await connector.GetConnected().SearchAsync(query, maxResults, true);
message = "...using normal Query search, Query " + query + ", max results " + maxResults.ToString();
}
}
catch (IQserException ex)
{
message = ex.Message;
}
}
if (results != null)
{
ICollection<LocalSearchResult> contentResults = new List<LocalSearchResult>();
foreach (SearchResult s in results)
{
var q = s.ToString();
var contentItem = await connector.GetConnected().GetContentAsync(s.ContentId);
LocalSearchResult lContent = new LocalSearchResult(contentItem);
lContent.Score = s.Score;
lContent.Relevance = s.Relevance;
lContent.MarkFullText(query);
contentResults.Add(lContent);
}
At the point where I call s.ToString() method, I get an error "Resource Map not found".
To explain where this comes from:
public static class AppResources
{
private static ResourceLoader resourceLoader;
static AppResources()
{
// Load local file Resources.resw by default
resourceLoader = new ResourceLoader();
}
public static string GetResources(string key)
{
if (string.IsNullOrEmpty(key))
throw new ArgumentNullException("key");
return resourceLoader.GetString(key);
}
}
and inside the overridden ToString() method there is code that looks as follows:
public override string ToString()
{
StringBuilder buf = new StringBuilder(AppResources.GetResources("InstrSearchResultContent"));
if (ContentId != -1)
{
buf.Append(AppResources.GetResources("StringContent") + " ID:" + ContentId.ToString() + " | ");
}
else
{
buf.Append(AppResources.GetResources("StringNo") + AppResources.GetResources("StringContent") + "ID" + " | ");
}
...
The resource file is called resources.resw and is the default resw file that ResourceLoader calls if no other is called.
Strangely enough, if I copy the resource file inside the client application locally, it is referenced correctly by all calls to the class library resource file and everything works.
This class library is supposed to be an SDK when finished. Do I need to distribute the resource file separately?
Such a problem I have never experienced with normal Class libraries and resx files. Resw is giving me the creeps..
It looks like you have to specify the name of the resource map when you create the ResourceLoader, like this:
resourceLoader = new ResourceLoader("Assembly/ResourceFile");
For example, if your class library was called "Company.Lib.dll", and your resource file was "Resources.resw", you would use:
resourceLoader = new ResourceLoader("Company.Lib/Resources");
This doesn't seem to be documented fully on MSDN - it suggests that you can just specify the name of your resource file, but it might be that that only works for resource files that are in the Windows Store application project. It was this page that showed me that, for libraries, you need to specify the assembly name as well.
I also had similar issue even with repeating all steps from How to load string resources.
The problem was that my Resources.resw file was empty. When I added some fake string to it all started working as expected.
I had a similar issue which i resolved by changing the Build Action of the resw file to PRIResource in the properties. I had renamed an existing resx to resw but the documentation doesn't mention that you also have to change the build action.
Accepted answer posted by #Rory MacLeod may no longer be true. I tried and VS warned that ResourceLoader(String) is deprecated. The following worked in my case:
var loader = ResourceLoader.GetForCurrentView();
string localName = loader.GetString("someKey");
I faced a similar issue when developing a UWP app with a class library.
So I have a /Strings/en-Us/Resource.resw file in my library.
ResourceLoader.GetForCurrentView().GetString("someKey");
gives an exception
new ResourceLoader("Company.Lib/Resources").GetString("someKey");
gives me a deprecation warning but works.
My solution which does not give a warning is this:
ResourceLoader.GetForViewIndependentUse("AssemblyNamespace/Resources").GetString("someKey");
i am very new to C#, and this is my first question, please be gentle on me
I am trying to write a application to capture some tick data from the data provider, below is the main part of the program
void zf_TickEvent(object sender, ZenFire.TickEventArgs e)
{
output myoutput = new output();
myoutput.time = e.TimeStamp;
myoutput.product = e.Product.ToString();
myoutput.type = Enum.GetName(typeof(ZenFire.TickType), e.Type);
myoutput.price = e.Price;
myoutput.volume = e.Volume;
using (StreamWriter writer = File.AppendText("c:\\log222.txt"))
{
writer.Write(myoutput.time.ToString(timeFmt) + ",");
writer.Write(myoutput.product + "," );
writer.Write(myoutput.type + "," );
writer.Write(myoutput.price + ",");
writer.Write(myoutput.volume + ",");
}
i have successfully write the data into the text file, however i know that this method will be call like 10000 times a second during peak time, and open a file and append it many times a second is very inefficient, i was pointed to use a buffer or some sort, but i have no idea how to do it, i try reading the document but i still dont understand, thats why i turn in here for help.
Please give me some (working) snippet code so i can pointed to the write direction. thanks
EDIT: i have simplified the code as much as possible
using (StreamWriter streamWriter = File.AppendText("c:\\output.txt"))
{
streamWriter.WriteLine(string.Format("{0},{1},{2},{3},{4}",
e.TimeStamp.ToString(timeFmt),
e.Product.ToString(),
Enum.GetName(typeof(ZenFire.TickType), e.Type),
e.Price,
e.Volume));
}
ED has told me to make my stream to a field, how is the syntax looks like? can anyone post some code to help me? thanks a lot
You need to create a field for the stream instead of a local variable. Initialize it in constructor once and don't forget to close it somewhere. It's better to implement IDisposable interface and close the stream in Dispose() method.
IDisposable
class MyClass : IDisposable {
private StreamWriter _writer;
MyClass() {
_writer = File.App.....;
}
void zf_TickEvent(object sender, ZenFire.TickEventArgs e)
{
output myoutput = new output();
myoutput.time = e.TimeStamp;
myoutput.product = e.Product.ToString();
myoutput.type = Enum.GetName(typeof(ZenFire.TickType), e.Type);
myoutput.price = e.Price;
myoutput.volume = e.Volume;
_writer.Write(myoutput.time.ToString(timeFmt) + ",");
_writer.Write(myoutput.product + "," );
_writer.Write(myoutput.type + "," );
_writer.Write(myoutput.price + ",");
_writer.Write(myoutput.volume + ",");
}
public void Dispose() { /*see the documentation*/ }
}
There are many things you can do
Step 1. Make sure you don't make many io calls and string concatenations.
Output myOutput = new Outoput(e); // Maybe consruct from event args?
// Single write call, single string.format
writer.Write(string.Format("{0},{1},{2},{3},{4},{5}",
myOutput.Time.ToString(),
myOutput.Product,
...);
This I recommend regardless of what your current performance is. I also made some cosmetic changes (variable/property/class name casing. You should look up the difference between variables and properties and their recommended case etc.)
Step 2. Analyse your performance to see if it does what you want. If it does, no need to do anything further. If performance is still too bad, you can
Keep the file open and close it when your handler shuts down.
Write to a buffer and flush it at regular intervals.
Use a logger framework like log4net that internally handles the above for you, and takes care of hairy issues like access to the log file from multiple threads.
I would use String.Format:
using (StreamWriter writer = new StreamWriter(#"c:\log222.txt", true))
{
writer.AutoFlush = true;
writer.Write(String.Format("{0},{1},{2},{3},{4},", myoutput.time.ToString(timeFmt),
myoutput.product, myoutput.type, myoutput.price, myoutput.volume);
}
If you use # before string you don't have to use double \.
This is much faster - you write only once to the file instead of 5 times. Additionally you don't use + operator with strings which is not the fastest operation ;)
Also - if this is multithreading application - you should consider using some lock. It would prevent application from trying to write to the file from eg. 2 threads at one time.
I've done my reading and understand what a Try/Catch block does and why it's important to use one. But I'm stuck on knowing when/where to use them. Any advice? I'll post a sample of my code below in hopes that someone has some time to make some recommendations for my example.
public AMPFileEntity(string filename)
{
transferFileList tfl = new transferFileList();
_AMPFlag = tfl.isAMPFile(filename);
_requiresPGP = tfl.pgpRequired(filename);
_filename = filename.ToUpper();
_fullSourcePathAndFilename = ConfigurationSettings.AppSettings.Get("sourcePath") + _filename;
_fullDestinationPathAndFilename = ConfigurationSettings.AppSettings.Get("FTPStagePath") + _filename;
_hasBeenPGPdPathAndFilename = ConfigurationSettings.AppSettings.Get("originalsWhichHaveBeenPGPdPath");
}
public int processFile()
{
StringBuilder sb = new StringBuilder();
sb.AppendLine(" ");
sb.AppendLine(" --------------------------------");
sb.AppendLine(" Filename: " + _filename);
sb.AppendLine(" AMPFlag: " + _AMPFlag);
sb.AppendLine(" Requires PGP: " + _requiresPGP);
sb.AppendLine(" --------------------------------");
sb.AppendLine(" ");
string str = sb.ToString();
UtilityLogger.LogToFile(str);
if (_AMPFlag)
{
if (_requiresPGP == true)
{
encryptFile();
}
else
{
UtilityLogger.LogToFile("This file does not require encryption. Moving file to FTPStage directory.");
if (File.Exists(_fullDestinationPathAndFilename))
{
UtilityLogger.LogToFile(_fullDestinationPathAndFilename + " alreadyexists. Archiving that file.");
if (File.Exists(_fullDestinationPathAndFilename + "_archive"))
{
UtilityLogger.LogToFile(_fullDestinationPathAndFilename + "_archive already exists. Overwriting it.");
File.Delete(_fullDestinationPathAndFilename + "_archive");
}
File.Move(_fullDestinationPathAndFilename, _fullDestinationPathAndFilename + "_archive");
}
File.Move(_fullSourcePathAndFilename, _fullDestinationPathAndFilename);
}
}
else
{
UtilityLogger.LogToFile("This file is not an AMP transfer file. Skipping this file.");
}
return (0);
}
private int encryptFile()
{
UtilityLogger.LogToFile("This file requires encryption. Starting encryption process.");
// first check for an existing PGPd file in the destination dir. if exists, archive it - otherwise this one won't save. it doesn't overwrite.
string pgpdFilename = _fullDestinationPathAndFilename + ".PGP";
if(File.Exists(pgpdFilename))
{
UtilityLogger.LogToFile(pgpdFilename + " already exists in the FTPStage directory. Archiving that file." );
if(File.Exists(pgpdFilename + "_archive"))
{
UtilityLogger.LogToFile(pgpdFilename + "_archive already exists. Overwriting it.");
File.Delete(pgpdFilename + "_archive");
}
File.Move(pgpdFilename, pgpdFilename + "_archive");
}
Process pProc = new Process();
pProc.StartInfo.FileName = "pgp.exe";
string strParams = #"--encrypt " + _fullSourcePathAndFilename + " --recipient infinata --output " + _fullDestinationPathAndFilename + ".PGP";
UtilityLogger.LogToFile("Encrypting file. Params: " + strParams);
pProc.StartInfo.Arguments = strParams;
pProc.StartInfo.UseShellExecute = false;
pProc.StartInfo.RedirectStandardOutput = true;
pProc.Start();
pProc.WaitForExit();
//now that it's been PGPd, save the orig in 'hasBeenPGPd' dir
UtilityLogger.LogToFile("PGP encryption complete. Moving original unencrypted file to " + _hasBeenPGPdPathAndFilename);
if(File.Exists(_hasBeenPGPdPathAndFilename + _filename + "original_which_has_been_pgpd"))
{
UtilityLogger.LogToFile(_hasBeenPGPdPathAndFilename + _filename + "original_which_has_been_pgpd already exists. Overwriting it.");
File.Delete(_hasBeenPGPdPathAndFilename + _filename + "original_which_has_been_pgpd");
}
File.Move(_fullSourcePathAndFilename, _hasBeenPGPdPathAndFilename + _filename + "original_which_has_been_pgpd");
return (0);
}
}
}
The basic rule of thumb for catching exceptions is to catch exceptions if and only if you have a meaningful way of handling them.
Don't catch an exception if you're only going to log the exception and throw it up the stack. It serves no meaning and clutters code.
Do catch an exception when you are expecting a failure in a specific part of your code, and if you have a fallback for it.
Of course you always have the case of checked exceptions which require you to use try/catch blocks, in which case you have no other choice. Even with a checked exception, make sure you log properly and handle as cleanly as possible.
Like some others have said, you want to use try-catch blocks around code that can throw an Exception AND code that you are prepared to deal with.
Regarding your particular examples, File.Delete can throw a number of exceptions, for example, IOException, UnauthorizedAccessException. What would you want your application to do in those situations? If you try to delete the file but someone somewhere else is using it, you will get an IOException.
try
{
File.Delete(pgpdFilename + "_archive")
}
catch(IOException)
{
UtilityLogger.LogToFile("File is in use, could not overwrite.");
//do something else meaningful to your application
//perhaps save it under a different name or something
}
Also, keep in mind that if this does fail, then the File.Move you do outside of your if block next will also fail (again to an IOException - since the file was not deleted it is still there which will cause the move to fail).
I was taught to use try/catch/finally for any methods/classes where multiple errors could occur and that you can actually handle. Database transactions, FileSystem I/O, streaming, etc. Core logic usually doesn't require try/catch/finally.
The great part about try/catch/finally is that you can have multiple catches so that you can create a series of exception handlers to deal with very specific error or use a general exception to catch whatever errors you don't see coming.
In your case, you're using File.Exists which is good, but their maybe another problem with the disk that may throw another error that File.Exists cannot handle. Yes, it's a boolean method, but say the File is locked and what happens if you try to write to it? With the catch, you can plan for a rare scenario, but without try/catch/finally, you may be exposing the code to completely unforeseen conditions.
The other guys have given quite a number of good pointers and references.
My input is a short one:
When to use it is one thing, equally or more importanly is how to use it properly.
PS: "it" is refeings to "trying-catching exceptions".