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I'm getting this error message on my laptop (win7 64bit/visual studio 2012 express), but not my desktop (win7 64bit/visual studio 2012 pro), code is unchanged.
This is happening when my code runs through Quote: var versionPtr = GetPropellerVersion();
Which is a dll import call via the code below, so it has something to do with the unmanaged code, but I'm a bit confused as to why? I believe the dll is 32 bit, so I've set the project to force x86, but I'm unsure as to what else could cause this? The project is set to 'copy always' the dll as well. I've also tried it in debug and release mode, same conflicting results.
Does anyone have any ideas? Thanks for reading.
Quote: [DllImport("Propellent.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr GetPropellerVersion();
Quote: Unhandled Exception: System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
at program.GetPropellerVersion()
at program.btnDetectPort_Click(Object sender, EventArgs e) in program\Form1.cs:line 1750
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NatiThe program '[48096] program.exe: Managed (v2.0.50727)' has exited with code -1073741819 (0xc0000005) 'Access violation'.
veWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(Form mainForm)
at program.Program.Main() in program\Program.cs:line 19
private void btnDetectPort_Click(object sender, EventArgs e)
{
cbxSerialPort.Items.Clear();
string[] ports = SerialPort.GetPortNames();
foreach (string port in ports)
{
cbxSerialPort.Items.Add(port);
cbxSerialPort.SelectedIndex = 0;
serialPort1.PortName = port;
serialPort1.BaudRate = 115200;
serialPort1.Encoding = Encoding.ASCII;
try
{
serialPort1.Open();
this.Invoke(new EventHandler(delegate
{
serialPort1.Close();
}));
}
catch (Exception)
{
}
}
var versionPtr = GetPropellerVersion();
string version = Marshal.PtrToStringAnsi(versionPtr);
int delimiter = version.IndexOf(':');
if (delimiter > -1)
{
string comPort = version.Remove(delimiter - 1);
string firmWare = version.Remove(0, delimiter + 2);
tbxPropPortFound.Text = comPort;
int comPortIndex = cbxSerialPort.FindString(comPort);
cbxSerialPort.SelectedIndex = comPortIndex;
}
}
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OK, so what is "GetPropellerVersion"? What does the import look like? What does the function do? Got any docs on this thing?
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Hi,
I had to upload it from my machine, it's a pdf. If you're sketched out about downloading a random pdf, I copied the text below and pasted it in a code block, it's the same thing, just not as pretty as the pdf.
http://temp-host.com/download.php?file=fv01pq[^]
[code]
Parallax Propellent
The Parallax Propellent software is a Windows-based tool for compiling and downloading to the Parallax Propeller chip. Propellent is available as both a library (Propellent.dll) and as an executable (Propellent.exe).
ï‚·ï€ The Propellent Library (DLL) is for software developers to link into applications enabling immediate support of the Propeller using the same functions as the Parallax-made Propeller Tool development software.
ï‚·ï€ The Propellent Executable (EXE) is a program that includes the Propellent Library within it and provides many of the same functions to anyone wishing for command-line support of the Propeller chip.
This document is written for the Propellent Library. For details about the Propellent Executable, see the "Propellent Executable.pdf" document, or run the executable with the '/help' switch. For more information on the
Parallax Propeller chip and tools, please visit http:
Features of the Propellent Library:
ï‚·ï€ Can download Propeller Application images (.binary or .eeprom) to Propeller chips.
ï‚·ï€ Can compile Propeller source (.spin) for downloading, for saving as a binary or eeprom image, for retrieval of source document, or just for syntax checking.
ï‚·ï€ Can run with full, limited, or no visual feedback.
ï‚·ï€ Includes the Propeller Tool's multi-threaded serial port handling and Propeller chip communication functionality.
ï‚·ï€ Includes the Propeller Tool's dialogs for indicating serial port access and download progress as well as the user-customizable serial port search options.
ï‚·ï€ Automatically stores user-modified preferences in the Windows Registry for use in future sessions. This can be disabled if desired.
ï‚·ï€ Allows access to current list of available serial ports.
ï‚·ï€ Allows calling application to view and/or specify preferences such as Library Path, Reset Signal (DTR, RTS, or both) and Serial Search Method (AUTO or specific port).
ï‚·ï€ Supports Win2K (and later) operating systems.
New in Propellent Library v1.3
For users of the previous Propellent Library (v1.2):
1) Fixed bug in SetSerialSearchRules that prevented the rule strings from being properly validated, cleaned, and updated.
For users of the previous Propellent Library (v1.1):
1) GetPropellerVersion has been updated to return a PChar instead of a LongWord. See details below.
2) New routines, GetGUIMode and SetGUIMode, allow manipulation of the amount of GUI-based messages that display during normal operation. See details below.
3) SaveImage routine now automatically creates any non-existing folders listed in the Filename path. See details below.
Propellent Library API
To use the Propellent Library (Propellent.dll):
1) Store the Propellent.dll file in your application's path.
2) Link the Propellent.dll library into your application either statically or dynamically, as desired, using whatever means required by your development tools.
3) Call InitPropellent to initialize internal library settings and specify options.
4) Call other routines as desired to get/set options, compile, find a Propeller chip and download to it.
5) Call FinalizePropellent, before unloading library or terminating application, to clean up settings and free memory used by the Propellent Library.
Important:
To Compile (with the CompileSource call; see below) the library folder path must first be set either by a previous session or by a call to SetLibraryPath.
1
Library API:
Calling Conventions: All library routines should be called using "cdecl" format.
Types: Boolean = True/False.
Byte = 8-bit integer.
LongWord = 32-bit unsigned integer or pointer.
PChar = 32-bit pointer to zero-terminated character string.
Pointer = 32-bit pointer to data.
Routine (parameters) Returns Description
InitPropellent (WinHandle, StorePrefs, RegPath) nothing REQUIRED. This routine initializes critical internal items for proper library function. This MUST be the first call made to the Propellent Library and
should be done only once per library loading (if dynamically linked) or application initialization (if statically linked).
WinHandle (LongWord) : Handle to calling application's main window.
StorePrefs (Boolean) : True = Propellent library automatically stores its preference items in the Windows registry for use by future sessions.
(See RegPath for default path). False = Propellent library does not save its settings; calling application is responsible
for maintaining preference items.
RegPath (PChar) : May be null (default) or a pointer to a string indicating the registry path in which to automatically store preference items.
This value is ignored if StorePrefs = False.
Set RegPath to null to use the default path. Set RegPath to the address of a path string to have the library
automatically store its settings in another path (such as your application's registry path); a new key will automatically be
appended to the path.
The default path is <rootkey>\SOFTWARE\ParallaxInc\Propeller\Propellent\<lib_reg_ver> where <rootkey> is
HKEY_CURRENT_USER, and <lib_reg_ver> is the library's registry version (ex: 1.0).
If not null, path must be a valid path within the HKEY_CURRENT_USER hive; do not include
"HKEY_CURRENT_USER\" in the path. If it doesn't already exist, the path plus the <lib_reg_key> will be created
automatically at the end of a session if a setting had been modified within that session.
GetLibraryVersion LongWord OPTIONAL. Call this to retrieve the Propellent Library's version in Binary Coded Decimal (BCD) #.# format. For example, a returned value of $10
means version 1.0.
GetResetSignal Byte OPTIONAL. Get Propeller chip reset signal preference. Returns 0, 1, or 2; 0 = toggle DTR (default), 1 = toggle RTS, 2 = toggle both DTR and RTS.
This setting is automatically saved and restored between sessions by the Propellent library if InitPropellent was called with StorePrefs = True.
SetResetSignal (Value) nothing OPTIONAL. Set Propeller chip reset signal preference. The default (DTR) will work for all true serial ports and for most USB-to-Serial devices,
however some USB-to-Serial devices only support RTS (not DTR). This option allows the user to set which pin (DTR, RTS, or both) is used to reset
the Propeller chip at the start of the identification or download process. This setting is automatically saved and restored between sessions by the
Propellent library if InitPropellent was called with StorePrefs = True.
Value (Byte) : 0 = toggle DTR (default), 1 = toggle RTS, 2 = toggle both DTR and RTS.
2
GetGUIMode Byte OPTIONAL. Get Propellent Graphical User Interface preference. Returns 0, 1, 2, or 3; 0 = all on (default), 1 = status messages only, 2 = dialogs
only, 3 = all off. This setting is automatically saved and restored between sessions by the Propellent library if InitPropellent was called with StorePrefs
= True.
SetGUIMode(Value) nothing OPTIONAL. Set Propellent Graphical User Interface preference. This option allows the user to specify how many GUI-based messages should be
displayed during normal operation; all messages, status (progress messages) only, dialogs (user prompts) only, or none. Note that this setting is
ignored for: 1) the ShowEditPorts function since that feature requires GUI interaction, and 2) any rare-occurrence user prompts such as a "File already
exists. Overwrite?" dialog. This setting is automatically saved and restored between sessions by the Propellent library if InitPropellent was called with
StorePrefs = True.
Value (Byte) : 0 = all on (default), 1 = show status (i.e.: progress messages) only, 2 = show dialogs (i.e.: user prompts) only, 3 = all off.
GetSerialSearchMethod LongWord OPTIONAL. Get serial search method preference. Returns 0 if set to auto-scan all available ports. Returns 1..n if set to scan only one port
(COM1..COMn). This setting is automatically saved and restored between sessions by the Propellent library if InitPropellent was called with
StorePrefs = True.
SetSerialSearchMethod (Value) nothing OPTIONAL. Set serial search method preference to either auto-scan all available ports (default) or scan a single port only. This option allows a user
to limit the scanning process to a specific serial port. This setting is automatically saved and restored between sessions by the Propellent library if
InitPropellent was called with StorePrefs = True.
Value (LongWord) : 0 = Auto (scan all available ports), 1..n = Scan only one port (COM1..COMn).
GetSerialSearchRules PChar OPTIONAL. Get serial search rules preference as a zero-terminated string. This function need only be called if the application is handing the
Propeller library's preferences manually (ie: InitPropellent was called with StorePrefs = False). The serial search rules may be changed by the user at
any time that the ShowEditPorts routine is called (allowing them to review the rules and modify them as desired). This setting is automatically saved
and restored between sessions by the Propellent library if InitPropellent was called with StorePrefs = True. NOTE: After calling this function, be
sure to copy the returned string to the caller's memory space before executing other Propellent functions which return a PChar.
SetSerialSearchRules (Value) nothing OPTIONAL. Call this to set the serial search rules preference if Propellent library is configured to not store its own preferences (ie: InitPropellent was
called with StorePrefs = False). If Propellent library is configured to store its own preferences (recommended), simply ignore the Set/Get-
SerialSearchRules routines. The format and content of the serial search rules preference is all handled by the Propellent library; do not edit the value,
but rather, call this procedure if you wish to manually set it to a value saved from a previous session. To get the current setting call the
GetSerialSearchRules function. This setting is automatically saved and restored between sessions by the Propellent library if InitPropellent was called
with StorePrefs = True.
Value (PChar) : A pointer to a zero-terminated string containing the serial search rules to use.
GetLibraryPath PChar OPTIONAL. Get the path to the Propeller Library files that will be used for source code compiling operations. This setting is automatically saved and
restored between sessions by the Propellent library if InitPropellent was called with StorePrefs = True. NOTE: After calling this function, be sure to
copy the returned string to the caller's memory space before executing other Propellent functions which return a PChar.
SetLibraryPath (Value) nothing REQUIRED IF USING COMPILE FEATURES. Call this to set the path to the Propeller Library files that will be used for source code compiling
operations. The library path must be set before calling CompileSource. If library path was set in a prior session, and InitPropellent was called with
StorePrefs = True, there is no need to call SetLibraryPath unless the path needs to be changed.
Value (PChar) : A pointer to a zero-terminated string containing the fully-qualified path to the Propeller library; example:
3
C:\Program Files\Parallax Inc\Propeller Tool
ShowEditPorts nothing OPTIONAL. Call this to display the Serial Port Search List dialog. This dialog describes the computer's serial ports and the order in which the library
will search them when scanning for a Propeller chip. The user is able to reorder the list of ports and can create simple or advanced rules indicating
which serial ports to include or exclude for scanning. The library manages the settings created by the user via this dialog and, if InitPropellent was
called with StorePrefs = True, automatically stores those settings in the Windows registry for persistance across sessions.
GetPorts (Scannable) PChar OPTIONAL. Call this to receive a pointer to a string containing a comma-delimited list of current serial ports on the computer. Call this at any time to
get an updated list since the available serial ports can change at any time as USB-to-Serial devices are connected/disconnected from the system.
NOTE: After calling this function, be sure to copy the returned string to the caller's memory space before executing other Propellent
functions which return a PChar.
Scannable (Boolean) : True = (recommended) string is filtered per preferences to include only desirable ports. False = string is unfiltered;
shows every serial port currently on the computer in the order given by the system.
CompileSource (Filename, ShowError) Pointer OPTIONAL. Call this to compile a Propeller application from source code. Returns 0 (null) if compile was successful; returns non-zero if an error
occurred. After a successful compile, call DownloadToPropeller with a null Filename parameter to download this compiled Propeller application to the
Propeller chip. NOTE: Propeller source files may be either ANSI-encoded (one byte per character) or Unicode-encoded (UTF-16; two bytes per
character).
RETURN VALUE : 0 (null) = compile was successful.
Non-zero = compile failed. Returned value is a pointer to the following structure:
SrcFile (PChar) : A zero-terminated string containing the fully qualified path and file name of the source
code that caused the error.
SrcStart (LongWord) : The first character of the source causing the error (0-based).
SrcCount (LongWord) : The number of characters causing the error.
Error (PChar) : A zero-terminated string containing the error text message.
Note that Propeller source files may be either ANSI-encoded (one byte per character) or Unicode-encoded (UTF-16;
two bytes per character). Also, before compiling, the source is automatically translated to use single carriage return
(CR) characters for line ends. Keep these details in mind when interpreting the SrcStart and SrcCount fields of the
returned error structure.
Filename (PChar) : This parameter must either be null or must be a pointer to a zero-terminated string containing the fully-qualified path to
a folder or to a file that is the top object (source code) to compile. The Propellent Library will automatically load and
compile any subobjects called for in the Filename object as needed.
Filename <> null: If Filename indicates a path to a folder, an Open dialog will appear (with that folder selected) to allow
the user to choose a source file to be compiled. NOTE: To specify a folder, Filename must end with a trailing path
delimiter '\'; for example: C:\Temp\ indicates the Temp folder on the C drive. If Filename indicates a valid path and file,
that file will be opened automatically (no dialog will appear) and will be compiled.
Filename = null: An open dialog will appear with the last-accessed folder selected to allow the user to choose a source
file to be compiled.
ShowError (Boolean) : True = on error, show an error dialog before returning to caller. False = on error, immediately return to caller.
4
CompileSourceDocs (Filename) PChar OPTIONAL. Call this to compile and retrieve documentation for source file given by Filename. Returns 0 (null) if failed; returns pointer to zero-
terminated document string if successful.
RETURN VALUE : 0 (null) = failed.
Non-zero = success. Returned value is a pointer to a z-string containing the document.
Filename (PChar) : This parameter must either be null or must be a pointer to a zero-terminated string containing the fully-qualified path to
a folder or to a file to retrieve the document for.
Filename <> null: If Filename indicates a path to a folder, an Open dialog will appear (with that folder selected) to allow
the user to choose a source file to retrieve the document for. NOTE: To specify a folder, Filename must end with a
trailing path delimiter '\'; for example: C:\Temp\ indicates the Temp folder on the C drive. If Filename indicates a valid
path and file, that file will be opened automatically (no dialog will appear).
Filename = null: An open dialog will appear with the last-accessed folder selected to allow the user to choose a source
file to retrieve documentation from.
GetSourceHierarchy PChar OPTIONAL. Call this after a successful call to CompileSource to retrieve the structure of the Propeller Application just compiled. The returned value
is a pointer to a contiguous array of elements representing the objects of the application from the first object (the top object) to the last object (the last
one referenced). Each element of the array returned consists of the following:
1 byte = Indicates the attributes (type, location, horizontal level) of the object in the hierarchy.
Bit 6 : 0 = source file, 1 = data file
Bits 5:4 : 00 = unused, 01 = work folder, 10 = library folder, 11 = dual (exists in both work and library
folders)
Bits 3:0 : Horizontal level of object (0 through 15), where 0 is the left-most level (the top object) and 1
through 15 are deeper levels (nestings) of child objects.
n bytes = full path and file name as a zero-terminated string
1 byte = zero-terminator for the above string
The end of the array is denoted by one last element that consists of just 2 bytes, both equal to zero.
SaveImage (AsBinary, Filename, ShowSaveAs) Boolean OPTIONAL. Call this after a successful call to CompileSource to save the compiled Propeller Application as a binary or EEPROM image.
AsBinary (Boolean) : True = save image as a .binary file. False = save image as a .eeprom file.
Filename (PChar) : A pointer to a zero-terminated string indicating the fully qualified path and filename for the image file to create. This
path and filename will appear in the Save As dialog, if ShowSaveAs is True. Path and filename may be the source's file
name, in which case the extension will be replaced with either .binary or .eeprom accordingly. If Filename ends with a
path delimiter, \, the image will be saved in that path with the original source filename and the appropriate extension. If
Filename ends with a non-path delimiter, the image will be saved using that path and filename; any given extension will
be replaced with .binary or .eeprom. Any folders in the path string that do not exist will be created automatically.
ShowSaveAs (Boolean) : True = show Save As dialog (containing Filename's path and file) for user to make adjustments as desired. False = do
not show Save As dialog; Filename must be a valid path and filename in this case.
GetPropellerVersion PChar OPTIONAL. Scan serial ports for a Propeller chip and display and return the port and version of the Propeller chip (if found) or an error message (if
5
not found). NOTE: After calling this function, be sure to copy the returned string to the caller's memory space before executing other
Propellent functions which return a PChar.
RETURN VALUE : Returned value is a pointer to a z-string containing one of the following:
if success: COM# : VERSION #
if failure: <error message>
DownloadToPropeller (Filename, DownloadCmd) nothing OPTIONAL. Scan serial ports for a Propeller chip and download a compiled Propeller Application to it. The "application" may be either an existing
image file or the last successfully compiled application.
Filename (PChar) : This parameter must either be null or must be a pointer to a zero-terminated string containing the fully-qualified path to
a folder or file.
Filename <> null: If Filename indicates a path to a folder, an Open dialog will appear (with that folder selected) to allow
the user to choose an image file to be downloaded. NOTE: To specify a folder, Filename must end with a trailing path
delimiter '\'; for example: C:\Temp\ indicates the Temp folder on the C drive. If Filename indicates a valid path and file,
that file will be opened automatically (no dialog will appear) and will be downloaded to the Propeller.
Filename = null: The image of the last successfully compiled application (via a call to CompileSource) will be
downloaded to the Propeller.
DownloadCmd (Byte) : 1 = write to RAM and run, 2 = write to EEPROM and stop, 3 = write to EEPROM and run. NOTE: command 2 is not
currently used by the Propeller Tool software.
FinalizePropellent nothing REQUIRED. This routine cleans up internal items, like memory, used by the library. This must be called just before unloading the Propellent Library
(if dynamically linked), or just before application termination (if statically linked).
6
[/code]
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Does the error occur on the GetPropellerVersion line or the line after it? Using that return value as a pointer is going to be a bad thing 'cause it's not a memory address to a string.
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It's returning the numeric values on the left and the code converts it to the text value on the right hand side of the = sign.
112905168 = "COM6 : VERSION 1"
81416960 = "COM6 : VERSION 1"
How do those values equal the text? Are they memory addresses?
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No, it's not a memory address. It tells you in the documentation exactly what that value is.
Quote: RETURN VALUE : Format is Bits 31 [to] 16 = port id, bits 15 [to] 0 = version
It's single 32-bit value that returns 2 values. The 32-bits is divided into two fields. You've to do a bit of math to get the values separated.
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It fails on the var version = call propeller function line, but only on that one machine (so far). I read the documentation with the 2 words in the long, can you explain how they are converting the numeric value to text? I had it print out as binary and I still couldn't figure out how it was being converted?
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Where are you getting the text from??
NM. I just found in it in the code you originally posted. If it is an address, which your code seems to indicate it is, then the library is just storing a string and passing the address to you.
But, if this really is the case, the documentation doesn't match what the library is doing and you should direct all further queries about this library to the people who wrote it.
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Ok that confirms my confusion. There is another way to get the same value by using an int instead of a ptr (if I remember correctly), I will check my code and post that as well when I get home to see if heads or tails can be made of that.
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I'm not sure why this would behave differently on different win7 machines ... but calling the InitPropellent function in form1_load fixed this issue? Strange eh?
InitPropellent((long)this.Handle, false, "");
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No, not strange. You just converted the Handle value to a 64-bit integer. This tells me that your other machine where it works is a 32-bit machine and your Win7 machine is 64-bit.
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Both machines are actually 64 bit, although I have the project set to compile to 32 bit output since the dll is 32 bit.
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I would like to define a property that holds 3 chars, so Im thinking of an array. Is this the way to do it? Can it be done with an automatic property somehow?
public abstract class Package
{
private char[] request;
public Package()
{
request = new char[3];
}
public char[] Request
{
get { return request; }
set { request = value; }
}
}
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There are some ways you can do. What to choose, depends on your application, but most likely, way 1 and 2 will be most helpful to you.
- Use an array, as you did. If you do this, check for the length when the array is changed:
set
{
if (value.Length == 3)
{
request = value;
}
else
{
throw new Exception("Length of Request must be 3.");
}
}
- Use a
Tuple: http://msdn.microsoft.com/en-us/library/system.tuple%28v=vs.110%29.aspx[^]
private Tuple<char, char, char> request;
public Package()
{
request = new Tuple<char, char, char>('\0', '\0', '\0');
}
public Tuple<char, char, char> Request
{
get { return request; }
set { request = value; }
}
Items in the Tuple can be accessed like Request.Item1, Request.Item2, Request.Item3.
- As properties in your class. Personally, I wouldn't use this unless it is really necessary for some reason.
private char _char1;
private char _char2;
private char _char3;
public Package()
{
_char1 = _char2 = _char3 = '\0';
}
public char Char1
{
get { return _char1; }
set { _char1 = value; }
}
The quick red ProgramFOX jumps right over the Lazy<Dog>.
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Arrays are so last century. Better options would be a string, a Tuple, a custom class or struct.
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As Piebald suggests, a struct would be a lot better than an array: an array is a reference type, so it both takes more space and is slower to use than a struct - which is a value type, so it is "inline data" rather than a separate heap allocation and a reference field. And you can name the struct fields, which should make your code more readable as well.
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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That code has the interesting issue that the returned array can easily, even accidentally, be used to mess up the state of the Package. That's not necessarily the Worst Thing Ever (it is always possible to mess up objects with reflection anyway), but it's something to at least be aware of.
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I think the "best practice" ... the implementation details ... will be an "organic" function of the way you intend to use this data-structure; including what you want your code to communicate to yourself, and, possibly, others, in the future.
One suggestion: before you draw any simple one-size-fits-all conclusions about how .NET allocates memory for Structs, and other "Value Types" compared to "Reference Types," please read Eric Lippert's two articles on this topic: [^], [^]. Eric is a gurus'-guru who was a key player in creating .NET for many years, and I think these articles provide a very valuable insight into what actually goes on in memory in .NET ... perhaps not it's not as clear-cut as many people think.
There are many ways you could implement this, from simple to fancy, from one-shot single-purpose to general-use multi-purpose; a few years ago I wrote a multi-purpose class for maintaining a set of selected Char that was, perhaps, too fancy: I just looked at the code tonight and wondered why I made it so elaborate ... but I have a "thang" for writing multi-purpose 
If you care to say more about your goals here, I'll respond, and I am sure others will.
«A man will be imprisoned in a room with a door that's unlocked and opens inwards ... as long as it does not occur to him to pull rather than push» Wittgenstein
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TMattC wrote: Can it be done with an automatic property
One further comment: an automatic property is one where the private backing-field is created for you by using the declarative syntax:
private char[] CharProp { set; get; }
The moment you specify a "body" for either the 'set or the 'get, it's no longer an automatic property, and, since it's clear your use-case would involved accessing characters within the Array here, you'd have to do that in the 'get, and, for that to be done, you'd have to have an value to use as an Index into the Array, and there's no way to "pass in" a value to be used internally in a 'get, or 'set.
The next version of C#, C#6, is going to add some features to Property declaration: [^].
Of course, with a Property whose Type is Array you can always use the 'SetValue and 'GetValue methods of the Array object; however, as you'll see in this example, 'GetValue returns a Type Object which will need to be cast to 'Char to be used in the way you probably want to use it.
private char[] CharProp { set; get; }
private void TestCharProp()
{
CharProp = new char[3] {'a', 'b', 'c'};
char value2 = (char) CharProp.GetValue(2);
CharProp.SetValue('x',2);
}That's not the type of code I'd write: no error check for null; no check for bounds; unnecessary cast required. But, you can write your own methods to 'set and 'get, of course that do validate and do avoid the cast.
«A man will be imprisoned in a room with a door that's unlocked and opens inwards ... as long as it does not occur to him to pull rather than push» Wittgenstein
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I am working with a FileSystemWatcher and intercepting 'FileCreated and 'FileChanged events: no problem there.
The file is kept open in a simple text editor application.
I read the file using this code:
private string[] theFileContents;
private void ReadTheFile(string thePath)
{
theFileContents = File.ReadAllLines(thePath);
}If I start with the file inside the watched folder, the first time I change the text in the text editor and save, I get the notification, and can verify I am reading the changed text.
The second time I edit and save in the text editor I get the "in use" error System.IO.IOException:
"The process cannot access the file because it is being used by another process.
If I start with the file outside the watched folder and then drag-drop it in: I get the 'created notification, and can read the file.
If I then edit the file in the text editor and save, I get the "in use" error again.
Is there a way to keep the file open for reading during multiple FileSystemWatcher events ?
If there isn't, I am thinking that maybe copying the file, and then reading the copy, and then discarding the copy is one possible strategy.
Appreciate your thoughts !
«A man will be imprisoned in a room with a door that's unlocked and opens inwards ... as long as it does not occur to him to pull rather than push» Wittgenstein
modified 2-Jan-15 8:25am.
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Whenever you open the file for writing, you establish an exclusive lock on it - and no other process can get access to the file for read or write. So you need to look at your "simple text editor" and find out exactly what it does with files - some (primitive) ones open the file for read and write and hold it until they are finished (which is a pain if you have automated backups running)
And that sample code opens the same file twice...first to create a FileStream, and then again to actually read the data. You don't need the stream at all:
theFileContents = File.ReadAllLines(thePath); creates it's own stream and reads the file through that. Try without the stream, and see if the problem goes away.
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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Thanks, Griff,
Using only File.ReadAllText this happens:
Test 1
1. text file is open in NotePad++ and has been saved to the Desktop
2. drag-drop file into watched folder: created event fires, no error, file read as expected
3. change text in the file in NotePad++ and save without changing save-directory location: changed event fires; no error, file read as expected
4. change text in NotePad++ again: "in use" error
Test 2
1. text file is open in NotePad++ and has been saved to watched folder before the .NET is run
2. change text in the file in NotePad++:
first, and second edits/and/saves to same location:
changed event fires; no error, file read as expected
third edit and save to same location: "in use" error
Happy New Year !
«A man will be imprisoned in a room with a door that's unlocked and opens inwards ... as long as it does not occur to him to pull rather than push» Wittgenstein
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I wonder if it's Notepad also monitoring the file it "has open" even though it's closed it so that it can track changes outside the editor - I use PSPad which does that - and the two processes are getting the notification at the same time and one is finding the file in use as a result?
Might be worth a sleep-retry-sleep-retry to give it another chance?
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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Thanks again, Griff,
I am able to work around the problem by simply copying the dragged-dropped/changed file, then reading/processing the copied file, then deleting the copy. So, obviously, I do not alter the original in this scenario.
cheers, Bill
«A man will be imprisoned in a room with a door that's unlocked and opens inwards ... as long as it does not occur to him to pull rather than push» Wittgenstein
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If I helped, then you are welcome! 
Somehow, I don't think I did...
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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