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• Problem with waveOutWrite and waveOutGetPosition deadlock

  - by MusiGenesis

  I'm working on an app that plays audio continuously using the waveOut... API from winmm.dll. The app uses "leapfrog" buffers, which are basically a bunch of arrays of samples that you dump into the audio queue. Windows plays them seamlessly in sequence, and as each buffer completes Windows calls a callback function. Inside this function, I load the next set of samples into the buffer, process them however, and then dump the buffer back into the audio queue. In this way, the audio plays indefinitely. For animation purposes, I'm trying to incorporate waveOutGetPosition into the application (since the "buffer done" callbacks are irregular enough to cause jerky animation). waveOutGetPosition returns the current position of playback, so it's hyper-precise. The problem is that in my application, making calls to waveOutGetPosition eventually causes the application to lock up - the sound stops and the call never returns. I've boiled things down to a simple app that demonstrates the problem. You can run the app here: http://www.musigenesis.com/SO/waveOut%20demo.exe If you just hear a tiny bit of piano over and over, it's working. It's just meant to demonstrate the problem. The source code for this project is here: http://www.musigenesis.com/SO/WaveOutDemo.zip The first button runs the app in leapfrog mode without making the calls to waveOutGetPosition. If you click this, the app will play forever without breaking (the X button will close it and shut it off). The second button starts the leapfrogger and also starts a forms timer that calls the waveOutGetPosition and displays the current position. Click this and the app will run for a short while and then lock up. On my laptop, it usually locks up in 15-30 seconds; at most it's taken a minute. I have no idea how to fix this, so any help or suggestions would be most welcome. I've found very few posts on this issue, but it seems that there is a potential deadlock, either from multiple calls to waveOutGetPosition or from calls to that and waveOutWrite that occur at the same time. It's possible that I'm calling this too frequently for the system to handle.

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• Problem with waitable timers in Windows (timeSetEvent and CreateTimerQueueTimer)

  - by MusiGenesis

  I need high-resolution (more accurate than 1 millisecond) timing in my application. The waitable timers in Windows are (or can be made) accurate to the millisecond, but if I need a precise periodicity of, say, 35.7142857141 milliseconds, even a waitable timer with a 36 ms period will drift out of sync quickly. My "solution" to this problem (in ironic quotes because it's not working quite right) is to use a series of one-shot timers where I use the expiration of each timer to call the next timer. Normally a process like this would be subject to cumulative error over time, but in each timer callback I check the current time (with System.Diagnostics.Stopwatch) and use this to calculate what the period of the next timer needs to be (so if a timer happens to expire a little late, the next timer will automagically have a shorter period to compensate). This works as expected, except that after maybe 10-15 seconds the timer system seems to get bogged down, and a few timer callbacks here and there arrive anywhere from 25 to 100 milliseconds late. After a couple of seconds the problem goes away and everything runs smoothly again for 10-15 seconds, and then the stuttering again. Since I'm using Stopwatch to set each timer period, I'm also using it to monitor the arrival times of each timer callback. During the smooth-running periods, most (maybe 95%) of the intervals are either 35 or 36 milliseconds, and no intervals are ever more than 5 milliseconds away from the expected 35.7142857143. During the "glitchy" stretches, the distribution of intervals is very nearly identical, except that a very small number are unusually large (a couple more than 60 ms and one or two longer than 100 ms during maybe a 3-second stretch). This stuttering is very noticeable, and it's what I'm trying to fix, if possible. For the high-resolution timer, I was using the extremely antique timeSetEvent() multimedia timer from winmm.dll. In pursuit of this problem, I switched to using CreateTimerQueueTimer (along with timeBeginPeriod to set the high-resolution), but I'm seeing the same problem with both timer mechanisms. I've tried experimenting with the various flags for CreateTimerQueueTimer which determine which thread the timer runs on, but the stuttering appears no matter what. Is this just a fundamental problem with using timers in this way (i.e. using each one-shot timer to call the next)? If so, do I have any alternatives? One thing I was considering was to determine how many consecutive 1-millisecond-accuracy ticks would keep my within some arbitrary precision limit before I need to reset the timer. So, for example, if I wanted a 35.71428 period, I could let a 36 ms timer elapse 15 times before it was off by 5 milliseconds, then kill it and start a new one.

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• Help with string manipulation function

  - by MusiGenesis

  I have a set of strings that contain within them one or more question marks delimited by a comma, a comma plus one or more spaces, or potentially both. So these strings are all possible: BOB AND ? BOB AND ?,?,?,?,? BOB AND ?, ?, ? ,? BOB AND ?,? , ?,? ?, ? ,? AND BOB I need to replace the question marks with @P#, so that the above samples would become: BOB AND @P1 BOB AND @P1,@P2,@P3,@P4,@P5 BOB AND @P1,@P2,@P3,@P4 BOB AND @P1,@P2,@P3,@P4 @P1,@P2,@P3 AND BOB What's the best way to do this without regex or Linq?

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• Help with SqlCeChangeTracking

  - by MusiGenesis

  I'm trying to use a new class in SqlCe 3.5 SP2 called SqlCeChangeTracking. This class (allegedly) lets you turn on change tracking on a table, without using RDA replication or Sync Services. Assuming you have an open SqlCeConnection, you enable change tracking on a table like this: SqlCeChangeTracking tracker = new SqlCeChangeTracking(conn); tracker.EnableTracking(TableName, TrackingKeyType.PrimaryKey, TrackingOptions.All); This appears to work, sort of. When I open the SDF file and view it in SQL Server Management Studio, the table has three additional fields: __sysChangeTxBsn, __sysInsertTxBsn and __sysTrackingContext. According to the sparse documentation, these columns (along with the __sysOCSDeletedRows system table) are used to track changes. The problem is that these three columns always contain NULL values for all rows, no matter what I do. I can add, delete, edit etc. and those columns remain NULL no matter what (and no deleted records ever show up in __sysOCSDeletedRows). I have found virtually no documentation on this class at all, and the promised MSDN API appears non-existent. Anybody know how to use this class?

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• Problem using FtpWebRequest to append to file on a mainframe

  - by MusiGenesis

  I am using FtpWebRequest to append data to a mainframe file. Each record appended is 50 characters long, and I am adding them one record at a time. In our development environment, we do not have a mainframe, so my code was written and tested FTPing to a Windows-based FTP site instead of a mainframe. Initially, I was writing each record using a StreamWriter (using the stream from the FtpWebRequest) and writing each record using WriteLine (which automatically adds a CR/LF to the end). When we ran this for the first time in the test environment (in which we're writing to an actual MVS mainframe), our mainframe contact said the CR/LFs were not able to be read by his program (a green-screen mainframe program of some sort - he's sent me screen captures, which is all I know of it). I changed our code to use Write instead of WriteLine, but now my code executes successfully (i.e no thrown exceptions) when writing multiple records, but no matter how many records we append, he is only able to "see" the first record - according to his mainframe program, there is only one 50-character record in the file. I'm guessing that to fix this, I need to write some other line-delimiting character into the end of the stream (instead of CR/LF) that the mainframe will recognize as a record delimiter. Anybody know what this is, or how else I can fix this problem?

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• Help with dynamic range compression function (audio)

  - by MusiGenesis

  I am writing a C# function for doing dynamic range compression (an audio effect that basically squashes transient peaks and amplifies everything else to produce an overall louder sound). I have written a function that does this (I think): public static void Compress(ref short[] input, double thresholdDb, double ratio) { double maxDb = thresholdDb - (thresholdDb / ratio); double maxGain = Math.Pow(10, -maxDb / 20.0); for (int i = 0; i < input.Length; i += 2) { // convert sample values to ABS gain and store original signs int signL = input[i] < 0 ? -1 : 1; double valL = (double)input[i] / 32768.0; if (valL < 0.0) { valL = -valL; } int signR = input[i + 1] < 0 ? -1 : 1; double valR = (double)input[i + 1] / 32768.0; if (valR < 0.0) { valR = -valR; } // calculate mono value and compress double val = (valL + valR) * 0.5; double posDb = -Math.Log10(val) * 20.0; if (posDb < thresholdDb) { posDb = thresholdDb - ((thresholdDb - posDb) / ratio); } // measure L and R sample values relative to mono value double multL = valL / val; double multR = valR / val; // convert compressed db value to gain and amplify val = Math.Pow(10, -posDb / 20.0); val = val / maxGain; // re-calculate L and R gain values relative to compressed/amplified // mono value valL = val * multL; valR = val * multR; double lim = 1.5; // determined by experimentation, with the goal // being that the lines below should never (or rarely) be hit if (valL > lim) { valL = lim; } if (valR > lim) { valR = lim; } double maxval = 32000.0 / lim; // convert gain values back to sample values input[i] = (short)(valL * maxval); input[i] *= (short)signL; input[i + 1] = (short)(valR * maxval); input[i + 1] *= (short)signR; } } and I am calling it with threshold values between 10.0 db and 30.0 db and ratios between 1.5 and 4.0. This function definitely produces a louder overall sound, but with an unacceptable level of distortion, even at low threshold values and low ratios. Can anybody see anything wrong with this function? Am I handling the stereo aspect correctly (the function assumes stereo input)? As I (dimly) understand things, I don't want to compress the two channels separately, so my code is attempting to compress a "virtual" mono sample value and then apply the same degree of compression to the L and R sample value separately. Not sure I'm doing it right, however. I think part of the problem may the "hard knee" of my function, which kicks in the compression abruptly when the threshold is crossed. I think I may need to use a "soft knee" like this: Can anybody suggest a modification to my function to produce the soft knee curve?

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• How to get IMediaControl.Run() to start a file playing with no delay

  - by MusiGenesis

  I am attempting to use DirectShow to play two AVI files consecutively (one after the other) so that there is no interruption in the audio or video when the player transitions from one file to the next. I have two custom controls on my form. Each one is pre-loaded with an AVI file, and before playback begins I set up all the DirectShow interfaces, set the video windows and resize them, call IMediaControl.Run(), then IMediaControl.Pause(), then IMediaSeeking.SetPositions to reset to frame 0, on both controls. On the form, you can see that both files are paused at their initial frames. I then call IMediaControl.Run() on the first control, and wait for it to complete before calling Run() on the second control. Initially, I hooked into the first video's EC_COMPLETE notification message, and used this to start the second. Thinking that this event might be slow to arrive (turns out it is, but for a weird reason), I tried two other approaches: Check the first video's current position inside a timer that goes off every second or so (using IMediaPosition.get_CurrentPosition). When the current position is within a second of the video's stop time (known in advance from IMediaPosition.get_StopTime), I go into a tight while loop and wait for the current position to equal the stop time, and then call Run() on the second video. Same as the first, except I replace the while loop with a call to timeSetEvent from winmm.dll, with a delay set so that it fires right when the first file is supposed to end. I use the callback to Run() the second file. Either of these two methods substantially cuts down the delay between the end of the first file and the beginning of the second, indicating that the EC_COMPLETE message doesn't arrive immediately after the file is complete (I also tried hooking the EC_SEGMENT_COMPLETE message, which is supposed to be used for looping within a file, but apparently nobody supports this - it never occurs on my machine, at least). Doing all of the above has cut the transition delay from as much as a second, down to a barely perceptible glitch; about a third of the time the files transition with no interruption at all, which suggests there's no fundamental reason I can't get this to work all the time. The slight delay is still unacceptable, unfortunately. I assume (and I could easily be wrong) that the remaining delay is due to a slight variable delay between the call to IMediaControl.Run() and when the video actually starts playing. Does anybody know anything I can do to eliminate this little lag? It would also help to be told this is fundamentally impossible for whatever reason, which wouldn't surprise me. I've never encountered a video player in Windows that doesn't have this problem, so it may not be doable. More info: the AVI files I'm playing are completely uncompressed (video and audio are uncompressed), so I don't think the lag is due to DirectShow's having to uncompress the video ahead of play start, although it may still buffer ahead as matter of course (and this may be the source of the problem). I would have though that starting play, pausing and then rewinding to the beginning would fix this. Also, the way I'm handling the transition is to actually have the second control underneath the first; when the first completes playing, I start the second and then call BringToFront on it, creating the appearance of a single video transitioning between the two originals. I don't think the glitch is due to this, because it works perfectly some of the time, and even if this were problematic, it wouldn't explain the matching audio glitch. Even more: I just tried starting the second video 30-50 milliseconds "early" and that seemed to eliminate even more of the gap, so I'm guessing that the lag in Run() is about that long. It appears to be variable, though, so this is still not where I need it to be.

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• How to access the Desktop Composition Engine from a WinForms app?

  - by MusiGenesis

  Is it possible to access Desktop Composition Engine in Windows Vista from a winforms application? The DCE apparently involves applications rendering to DCE buffers instead of directly to the screen. Since a winforms app has no way of getting information about the monitor's refresh rate and scanline status (other than via DirectX), animation in a winforms app is subject to tearing effects. With DCE enabled, the tearing effects are lessened but still there (apparently the DCE can still grab a buffer that your app is halfway through writing to and render it to the screen, thereby producing the half-one-frame-half-of-the-next tearing effects). Is there any way for my winforms app to communicate with the DCE and possible avoid rendering during buffer switchover times?

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• What is the worst C#/.NET gotcha?

  - by MusiGenesis

  This question is similar to this one, but focused on C# and .NET. I was recently working with a DateTime object, and wrote something like this: DateTime dt = DateTime.Now; dt.AddDays(1); return dt; // still today's date! WTF? The intellisense documentation for AddDays says it adds a day to the date, which it doesn't - it actually returns a date with a day added to it, so you have to write it like: DateTime dt = DateTime.Now; dt = dt.AddDays(1); return dt; // tomorrow's date This one has bitten me a number of times before, so I thought it would be useful to catalog the worst C# gotchas.

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• How can I overwrite a System.Drawing.Bitmap onto an existing GDI bitmap?

  - by MusiGenesis

  If I have a .Net Bitmap, I can create from it a GDI bitmap by calling the Bitmap's GetHbitmap() method. Bitmap bmp = new Bitmap(100, 100); IntPtr gdiBmp = bmp.GetHbitmap(); This works fine, but every time you call GetHbitmap, Windows has to allocate new memory for the object that gdiBmp references. What I'd like to do - if possible - is write a function (I know PInvoke will be necessary here) that also generates a GDI bitmap copy of a Bitmap, but that uses an existing object instead of allocating a new one. So it would look something like this (if it were an extension method of Bitmap): //void OverwriteHbitmap(IntPtr gdi) Bitmap bmp1 = new Bitmap(100, 100); IntPtr gdi1 = bmp1.GetHbitmap(); Bitmap bmp2 = new Bitmap(100, 100); bmp2.OverwriteHbitmap(gdi1); How can I do this? I assume I'll need to know the structure of a GDI bitmap, and probably I can use LockBits and BitmapData for this, but I'm not sure exactly how.

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• BitBlt code not working

  - by MusiGenesis

  I'm trying to use this code to draw a Bitmap directly onto a PictureBox: Bitmap bmp = (Bitmap)Bitmap.FromFile(@"C:\Users\Ken\Desktop\Load2.bmp"); Graphics grDest = Graphics.FromHwnd(pictureBox1.Handle); Graphics grSrc = Graphics.FromImage(bmp); IntPtr hdcDest = grDest.GetHdc(); IntPtr hdcSrc = grSrc.GetHdc(); BitBlt(hdcDest, 0, 0, pictureBox1.Width, pictureBox1.Height, hdcSrc, 0, 0, (uint)TernaryRasterOperations.SRCCOPY); // 0x00CC0020 grDest.ReleaseHdc(hdcDest); grSrc.ReleaseHdc(hdcSrc); but instead of rendering the Bitmap's contents it just draws a solid block of nearly-black. I'm pretty sure the problem is with the source hDC, because if I change SRCCOPY to WHITENESS in the above code, it draws a solid white block, as expected. Note: this next snippet works fine, so there's nothing wrong with the bitmap itself: Bitmap bmp = (Bitmap)Bitmap.FromFile(@"C:\Users\Ken\Desktop\Load2.bmp"); pictureBox1.Image = bmp;

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• Multi-part question about multi-threading, locks and multi-core processors (multi ^ 3)

  - by MusiGenesis

  I have a program with two methods. The first method takes two arrays as parameters, and performs an operation in which values from one array are conditionally written into the other, like so: void Blend(int[] dest, int[] src, int offset) { for (int i = 0; i < src.Length; i++) { int rdr = dest[i + offset]; dest[i + offset] = src[i] > rdr? src[i] : rdr; } } The second method creates two separate sets of int arrays and iterates through them such that each array of one set is Blended with each array from the other set, like so: void CrossBlend() { int[][] set1 = new int[150][75000]; // we'll pretend this actually compiles int[][] set2 = new int[25][10000]; // we'll pretend this actually compiles for (int i1 = 0; i1 < set1.Length; i1++) { for (int i2 = 0; i2 < set2.Length; i2++) { Blend(set1[i1], set2[i2], 0); // or any offset, doesn't matter } } } First question: Since this apporoach is an obvious candidate for parallelization, is it intrinsically thread-safe? It seems like no, since I can conceive a scenario (unlikely, I think) where one thread's changes are lost because a different threads ~simultaneous operation. If no, would this: void Blend(int[] dest, int[] src, int offset) { lock (dest) { for (int i = 0; i < src.Length; i++) { int rdr = dest[i + offset]; dest[i + offset] = src[i] > rdr? src[i] : rdr; } } } be an effective fix? Second question: If so, what would be the likely performance cost of using locks like this? I assume that with something like this, if a thread attempts to lock a destination array that is currently locked by another thread, the first thread would block until the lock was released instead of continuing to process something. Also, how much time does it actually take to acquire a lock? Nanosecond scale, or worse than that? Would this be a major issue in something like this? Third question: How would I best approach this problem in a multi-threaded way that would take advantage of multi-core processors (and this is based on the potentially wrong assumption that a multi-threaded solution would not speed up this operation on a single core processor)? I'm guessing that I would want to have one thread running per core, but I don't know if that's true.

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• Can SOTI's MobiControl software interfere with an ASP.Net web service?

  - by MusiGenesis

  We have a set of WinMo (5.0) devices running a .NET CF application that talks to an ASP.Net web service running on a server. The devices connect to the network either via ActiveSync through a networked PC or directly to the network via an Ethernet dongle. In our development environment, the communication between devices and web service is 100% reliable. In our production environment, the communications are failing erratically and unpredictably. Sometimes calls to the web service (even to a simple test call that just returns a boolean) begin failing every time on a particular device, with the error message "Could not establish connection to network." This is usually fixed by flip-flopping the selected combo box values on the SETTINGS | NETWORKS screen. Sometimes calls on a particular device begin failing with a generic "WebException" message. The fix for this problem (so far) is either to reset the device (i.e. reinstall the OS) or else it just can't be fixed on some devices. To the best of our knowledge, everything about the DEV and PROD systems are the same (same server and device specs). The most obvious difference to us is that the PROD devices are all controlled by SOTI's MobiControl (which is server-side software that communicates with a SOTI client application installed on each device), whereas our DEV environment does not have SOTI installed anywhere (obviously we should have it there as well - long story). Does anybody have any experience with SOTI MobiControl and/or know of any documented problems where SOTI interferes with other communication mechanisms on a device?

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• Problem using UnhandledException in Windows Mobile app

  - by MusiGenesis

  I have a Windows Mobile program that accesses an attached device through a third-party DLL. Each call to the device can take an unknown length of time, so each call includes a timeout property. If the call takes longer than the specified timeout to return, the DLL instead throws an exception which my app catches with no problem. The problem that I have is with closing the application. If my application has made a call to the DLL and is waiting for the timeout to occur, and I then close the application before the timeout occurs, my application locks up and requires the PDA to be rebooted. I can ensure that the application waits for the timeout before closing, under normal conditions. However, I am trying to use AppDomain.CurrentDomain.UnhandledException to catch any unhandled exceptions in the program and use the event to wait for this pending timeout to occur so the program can be closed finally. My problem is that this event doesn't seem to stick around long enough. If I put a MessageBox.Show("unhandled exception"); line in the event, and then throw a new unhandled exception from my application's main form, I see the message box for a split second but then it disappears without my having clicked the OK button. The documentation I've found on this event suggests that by the time it's called the application is fully committed to closing and the closing can't be stopped, but I didn't think it meant that the event method itself won't finish. What gives (I guess that's the question)? Update: In full windows (Vista) this works as expected, but only if I use the Application.ThreadException event, which doesn't exist in .Net CF 2.0.

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• What's a good way to copy files from a PC to a Windows Mobile device?

  - by MusiGenesis

  I have a C# application running on a server, and it needs to copy files out to multiple Windows Mobile 5.0 devices. These devices are connected to the network directly via Ethernet-enabled cradles (so they are not connected to a PC via ActiveSync). What different options do I have for doing this? I know RAPI can do this, but I'm not sure if it can copy something directly over the network like this. Also, I know RAPI uses ActiveSync DLLs and thus requires ActiveSync to be installed, and we would prefer to avoid doing this if possible. Is WMI a possibility? Can we use ordinary File.IO if we can somehow get the IP address of each device? Code samples or general knowledge would be most welcome.

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• Can the Windows Media Player COM control play AVI files from memory (instead of from a file)?

  - by MusiGenesis

  I have a C# app, and I'm looking at using the Windows Media Player COM control to play animation and audio. So far, the only way I see of programatically controlling what the control is playing is to set its URL property to point to some file (I assume there's some way to pass in a playlist). Is there any way the WMP can render an AVI that is entirely in-memory, like a MemoryStream or something? If so, can WMP skip from one AVI to the next seamlessly (i.e. no glitch in either the audio or the video as it transitions from one to the next)? If WMP only plays files, is there some way to cue up a list of the files in advance of play start? If so, can WMP be made to skip from one file to the next without a brief interruption? Any knowledge or links to knowledge would be much appreciated.

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• How can I limit access to a particular class to one caller at a time in a web service?

  - by MusiGenesis

  I have a web service method in which I create a particular type of object, use it for a few seconds, and then dispose it. Because of problems arising from multiple threads creating and using instances of this class at the same time, I need to restrict the method so that only one caller at a time ever has one of these objects. To do this, I am creating a private static object: private static object _lock = new object(); ... and then inside the web service method I do this around the critical code: lock (_lock) { using (DangerousObject do = new DangerousObject()) { do.MakeABigMess(); do.CleanItUp(); } } I'm not sure this is working, though. Do I have this right? Will this code ensure that only one instance of DangerousObject is instantiated and in use at a time?

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• How to keep an old VB6 application running in Windows Vista and Windows 7?

  - by MusiGenesis

  I have an old VB6 app which I'm still trying to support. A few users have reported weird crashes when running the app in Vista or Windows 7. The log files don't show anything after one of these crashes, but the customers report that the error message said "OLE something ...", if they saw anything at all. I've never been able to reproduce these crashes while running the program on my own Vista or Windows 7 boxes, so I have essentially no information on what the problem is. My suspicion is that it's a problem with their versions of one or more of the umpteen billion DLLs that a VB6 application is dependent on. The app also uses lame_enc.dll, which introduces a few more dependencies. I'm guessing this is a common problem with VB6 apps (although it's possible that I just sucked as a programmer 10 years ago). Is there some magical installer/updater out there that makes sure all the VB6 dependencies are what they need to be for a VB6 app to function properly?

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• Alternative to BitConverter.ToInt32

  - by MusiGenesis

  I'm using BitConverter.ToInt32 to pack 3 byte values into an int, like so: byte R = 0; byte G = 0; byte B = 0; int i = BitConverter.ToInt32(new byte[] { R, G, B, 0 }, 0); Is there a faster way to do this that doesn't involve the creation of a new int each time? Getting the bytes out of an int is easy: int i = 34234; byte B = (byte)(i >> 0); byte G = (byte)(i >> 8); byte R = (byte)(i >> 16); Is there a simple way to reverse this process and use bit-shifting to write the RGB bytes back over an existing int?

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• How to clean up after myself when drawing directly to the screen

  - by MusiGenesis

  I'm drawing directly to the screen using BitBlt and GetDC(IntPtr.Zero). Is there some way to call Refresh or Invalidate on the whole screen when I'm done, so that I don't leave bug chunks of paint everywhere (digitally speaking)?

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• Looking for a component (.NET or COM/ActiveX) that can play AVI files in a WinForms app

  - by MusiGenesis

  I'm looking for something like the Windows Media Player control that can be hosted on a form. The WMP doesn't work for me because I need a control that can play a continuously-appended playlist of AVI files in sequence, so that the transition from one file to the next happens seamlessly (i.e. without any glitches or pauses in the video and audio). With WMP, there's always a delay between files of half a second or so. Does anyone know of a control (it can be either commercial or open-source) that can do this? I assume anything like this wraps DirectX, and that's OK too.

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• Is there any way that an export-to-Excel function can be scalable?

  - by MusiGenesis

  Summary: ASP.Net website with a couple hundred users. Data is exported to Excel files which can be relatively large (~5 MB). In the pilot phase (just a few users), we are already seeing occasional errors on the server in the exporting method. Here's the stack trace: System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. --- System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown. at System.IO.MemoryStream.set_Capacity(Int32 value) at System.IO.MemoryStream.EnsureCapacity(Int32 value) at System.IO.MemoryStream.Write(Byte[] buffer, Int32 offset, Int32 count) at MS.Internal.IO.Packaging.TrackingMemoryStream.Write(Byte[] buffer, Int32 offset, Int32 count) at MS.Internal.IO.Packaging.SparseMemoryStream.WriteAndCollapseBlocks(Byte[ ] buffer, Int32 offset, Int32 count) at MS.Internal.IO.Packaging.SparseMemoryStream.Write(Byte[] buffer, Int32 offset, Int32 count) at MS.Internal.IO.Packaging.CompressEmulationStream.Write(Byte[] buffer, Int32 offset, Int32 count) at MS.Internal.IO.Packaging.CompressStream.Write(Byte[] buffer, Int32 offset, Int32 count) at MS.Internal.IO.Zip.ProgressiveCrcCalculatingStream.Write(Byte[] buffer, Int32 offset, Int32 count) at MS.Internal.IO.Zip.ZipIOModeEnforcingStream.Write(Byte[] buffer, Int32 offset, Int32 count) at System.IO.StreamWriter.Flush(Boolean flushStream, Boolean flushEncoder) at System.IO.StreamWriter.Write(String value) at System.Xml.XmlTextEncoder.Write(String text) at System.Xml.XmlTextWriter.WriteString(String text) at System.Xml.XmlText.WriteTo(XmlWriter w) at System.Xml.XmlAttribute.WriteContentTo(XmlWriter w) at System.Xml.XmlAttribute.WriteTo(XmlWriter w) at System.Xml.XmlElement.WriteTo(XmlWriter w) at System.Xml.XmlElement.WriteContentTo(XmlWriter w) at System.Xml.XmlElement.WriteTo(XmlWriter w) at System.Xml.XmlElement.WriteContentTo(XmlWriter w) at System.Xml.XmlElement.WriteTo(XmlWriter w) at System.Xml.XmlElement.WriteContentTo(XmlWriter w) at System.Xml.XmlElement.WriteTo(XmlWriter w) at System.Xml.XmlDocument.WriteContentTo(XmlWriter xw) at System.Xml.XmlDocument.WriteTo(XmlWriter w) at System.Xml.XmlDocument.Save(Stream outStream) at OfficeOpenXml.ExcelWorksheet.Save() in C:\temp\XXXXXXXXXX\ExcelPackage\ExcelWorksheet.cs:line 605 at OfficeOpenXml.ExcelWorkbook.Save() in C:\temp\XXXXXXXXXX\ExcelPackage\ExcelWorkbook.cs:line 439 at OfficeOpenXml.ExcelPackage.Save() in C:\temp\XXXXXXXXXX\ExcelPackage\ExcelPackage.cs:line 348 at Framework.Exporting.Business.ExcelExport.BuildReport(HttpContext context) at WebUserControl.BtnXLS_Click(Object sender, EventArgs e) in C:\TEMP\XXXXXXXXXX\XXXXXXXXXX\OneList\UserControls\TicketReportExporter. ascx.cs:line 108 at System.Web.UI.WebControls.Button.OnClick(EventArgs e) at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.Rai sePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace --- at System.Web.UI.Page.HandleError(Exception e) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) at System.Web.UI.Page.ProcessRequest(HttpContext context) at ASP.XXXXXXXXXXX_aspx.ProcessRequest(HttpContext context) in c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\XXXX\cdf32a52\d1a5eabd\App_Web_enxdwlks.1.cs:line 0 at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpAppli cation.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Even aside from this particular problem, in general exporting to Excel requires the instantiation of huge Excel objects on the server for each request, which I've always assumed to mean disqualifies Excel for "serious" work on a highly-loaded server. Is there any general way to export to Excel in a "light-weight" manner? Would simply streaming the data into a CSV file work for this?

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• How can I limit access to a particular class to one caller at a time in an ASMX web service?

  - by MusiGenesis

  I have a web service method in which I create a particular type of object, use it for a few seconds, and then dispose it. Because of problems arising from multiple threads creating and using instances of this class at the same time, I need to restrict the method so that only one caller at a time ever has one of these objects. To do this, I am creating a private static object: private static object _lock = new object(); ... and then inside the web service method I do this around the critical code: lock (_lock) { using (DangerousObject do = new DangerousObject()) { do.MakeABigMess(); do.CleanItUp(); } } I'm not sure this is working, though. Do I have this right? Will this code ensure that only one instance of DangerousObject is instantiated and in use at a time? Or does each caller get their own copy of _lock, rendering my code here laughable?

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• What is up with the unicorns?

  - by MusiGenesis

  It's only programming-related because they're here.

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• C# threading question

  - by MusiGenesis

  Is there any essential difference between this code: ThreadStart starter = new ThreadStart(SomeMethod); starter.Invoke(); and this? ThreadStart starter = new ThreadStart(SomeMethod); Thread th = new Thread(starter); th.Start(); Or does the first invoke the method on the current thread while the second invokes it on a new thread?

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