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In my current C# project, I am using an instance of the SerialPort class. I wanted to examine each character as it came in, so I registered a handler for the DataReceived event and set the ReceivedBytesThreshold property to 1. With these settings, I expected that the event handler would be called for each character received but I find that it only gets called once for every 5-8 characters. This is good for communication efficiency, but for what I want to do, I have to loop through the received characters in my event handler. Does anybody know if this is the expected behavior of this class?
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There is an interesting discussion of this question here[^]
The difficult we do right away...
...the impossible takes slightly longer.
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Thanks for the pointer.
--
Regards, Ken
I AM
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I am not surprised, asynchronous receive is a complex process, there are several actors, and some buffers with their sizes and thresholds, some of which one cannot control at all.
You should not be lazy and refuse to loop over the bytes you get in one go, that is pretty easy to accomplish.
It gets really nasty when you have to implement a message-oriented protocol, where the sender sends two or more messages back-to-back, and your receiver unfortunately receives three or more DataReceived events, each covering an arbitrary part of the messages sent (say first half of first msg, then second half+first half of second msg, finally second half of second message).
The only serial receive that goes smoothly is the one that has a fixed message separator (say a NEWLINE) which is guaranteed to appear in between messages and never inside a message (in that case set the NewLine property and use ReadLine). If that is not the case, get ready to collect what you get, whatever amount comes in, then re-packetize it according to your needs.
And then, you should carefully consider whether you need some recovery mechanism, something that helps you out in case some character gets damaged or lost...
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I am quite familiar with the intricacies of communication code. I have written a number of serial drivers for embedded systems over the past 20 years or so. My use of C# has been limited to writing "quick & dirty" utilities for testing my embedded systems. In this case, my code was working fine - I was just seeking a better understanding of the SerialPort class which did not behave as I expected and the Microsoft documentation for it is shallow at best.
--
Regards, Ken
I AM
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Greetings!
I would like to use Visual Studio's Database Designer to set up the data sets my application is going to need. But I am going to need the name of the database (or its DSN) to be configurable at run time. When I set up the objects, the connection string is stored in my applicaton's config file. But my application will have a separate settings file (an old-style .ini file). I would like to be able to change the connection string to whatever is contained in that file. How can I adjust the connection string before opening the database?
Thank you very much!
RobR
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Interrobang wrote: I would like to use Visual Studio's Database Designer to set up the data sets my application
This is a good idea when you first start out and are still learning but it is not a viable long term solution. Look into using a data access layer DAL, there are many examples here on CP.
Using a DAL will give you a much deeper understanding of where and how your data is manipulated. It will also make this question irrelevant as you will have all the control over your data access you need.
Never underestimate the power of human stupidity
RAH
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None of what you mentioned is professional grade, so you won't get much professional advice on how to do it.
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Hi guys,
how to show or hide caption video using AxWindowsMediaPlayer component?
I try with closeCaption but not work.
Thanks to all.
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what is the concept of it ???
how can i get one ???
I heard about "Unity" & other things but i am new in this field
I really need help ,,, thanks 
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A game engine is normally a black box piece of software that handles the internals of game creation, and provides an API for you to work with to create your own games. In a 3D game engine, for instance, the engine will take care of things such as loading textures and models, provide physics capabilities, lighting, etc.
As for where you can get one - there are several available, and there prices range from free up to several hundred thousand pounds depending on their target audience.
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Pete O'Hanlon wrote: prices range from free up to several hundred thousand pounds
...and from what I can tell, you get what you pay for!
Real men don't use instructions. They are only the manufacturers opinion on how to put the thing together.
Manfred R. Bihy: "Looks as if OP is learning resistant."
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OriginalGriff wrote: ...and from what I can tell, you get what you pay for!
Yes, and no 
Most of the expensive engines also have free versions for home or hobby use, and some only require licensing if you release a product commercially.
There are also some excellent free engines (oh, and some horrible commercial ones  As an ex-game developer I could tell you some horror stories about well-known engines...).
I'm not going to try to recommend a good engine, but DevMaster has a huge list of what's out there in all categories.
[ I've also just noticed there's a game development forum here now as well!  ]
Days spent at sea are not deducted from one's alloted span - Phoenician proverb
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Hi,
I need to get all installed languages on the computer. "Control Panel / Regional and Language / Keyboards and Languages / Display language". How can I get the selected language in .NET?
Our application has language settings for a lot of different languages. If our application don't has support for the selected language in "Display language" then we have to see if we has support for a fallback language.
I tried to use "GetThreadPreferredUILanguages" call and it work fine when I use C++, but I can't get is working on .NET. Is there an .NET call I can use instead to get selected languages and also the fallback languages?
C++ code
wchar_t buf[2323];
wchar_t *pBuf;
ULONG numLangs;
ULONG size= 2323;
GetThreadPreferredUILanguages(MUI_MERGE_USER_FALLBACK, &numLangs, buf, &
C# code
[DllImport("Kernel32.dll", CharSet = CharSet.Auto)]
static extern System.Boolean GetThreadPreferredUILanguages(
System.UInt32 dwFlags,
ref System.UInt32 pulNumLanguages,
out System.IntPtr pwszLanguagesBuffer,
ref System.UInt32 pcchLanguagesBuffer
);
uint MUI_MERGE_USER_FALLBACK = 0x20;
uint numLang = 0;
IntPtr pwszLangBuf = new IntPtr();
uint langBuf = 2323;
bool b = GetThreadPreferredUILanguages(MUI_MERGE_USER_FALLBACK, ref numLang, out pwszLangBuf, ref langBuf);
string tmp = Marshal.PtrToStringAuto(pwszLangBuf
tmp string variable contains only a lot of chinese characters after Marshal.PtrToStringAuto(pwszLangBuf);.
pulNumLanguages and pcchLanguagesBuffer returns the same in both C++ and C#.
See more information about GetThreadPreferredUILanguages on
http://msdn.microsoft.com/en-us/library/dd318128(v=vs.85).aspx[^]
What is wrong?
Regards
Olof
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Hi,
1. I'm not familiar with GetThreadPreferredUILanguages however I do know a thing or two about P/Invoke, and wrote a little article[^] on the subject. What you need here goes beyond the scope of my article though.
2. Your C# code is not doing what your C code does; in particular you should preallocate the result buffer, as you did with wchar_t buf[2323];. The native function you're calling expects a third parameter pwszLanguagesBuffer that is either a NULL, or a valid pointer to a buffer you provide for it to fill.
3. This seems like a reasonable approach: create a byte buffer, have it pinned (with GCHandle), call the native function, then use some kind of Marshal.PtrToString() for each string you need to extract from the buffer. Free the handle once all strings got extracted.
4. I would recommend you call GetThreadPreferredUILanguages twice, once without an output buffer (IntPtr.Zero), just to get the required buffer length; then the regular call with a sufficient buffer size.
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Have a look at the documentation for CultureInfo[^] and related classes.
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Hi
First of all please forgive me, I seem to be having a bit of a mental block! I've been trying to improve my exception handling and error logging.
I have a function ProcessPerson(). Within that function I call a ValidateUser() function. And within that function I call the GetAdmin() function. Would the following be acceptable or if not, how should it be done?
I have omitted unimportant code, so:
public void ProcessPerson(Request arg)
{
try
{
if(Class2.ValidateUser(arg.Username, arg.Role)
{
}
else
{
}
}
catch(ArgumentNullException ex)
{
}
catch(Exception ex)
{
}
}
public static bool ValidateUser(string Username, string Role)
{
try
{
using(MyClass myClass = new MyClass())
{
if(myClass.GetAdmin(Username, Role)
return true;
else
return false;
}
}
catch
{
throw;
}
}
public bool GetAdmin(string Username, string Role)
{
if(String.IsNullOrWhitespace(Username) || String.IsNullOrWhitespace(Role))
{
throw new ArgumentNullException("e.g. Username or Role cannot be null");
}
try
{
using(MyClassAdapter myClassAdapter = new MyClassAdapter ())
{
myClassAdapter.GetAdmin(Username, Role);
}
}
catch(ArgumentNullException ex)
{
throw;
}
catch(Exception ex)
{
throw;
}
}
Appreciate any help or advice.
Thanks
modified on Wednesday, September 14, 2011 5:01 AM
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try { ... } catch { throw; }
... is by definition pointless. Are you logging within that catch block? I don't think you should do that, though, because it will result in exceptions getting double-logged.
I would say you should trap exceptions at the point where it makes sense to handle them. You can make an argument for that being in ValidateUser (any exception should be 'invalid' i.e. return false), or at the top level call which might produce one (at which time you log the error). But don't catch it in both places.
You should only throw an ArgumentNullException if the argument is actually null – if you want to fail on empty too, it should be an ArgumentException. But 'guards' at the top of a method like that are fine.
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Thanks BobJanova.
The only reason I was using "try { ... } catch { throw; }" was to make sure the original exception was passed on to the top calling method that would handle the exception and log where the exception occurred.
Regarding ValidateUser, you're right, any exception should be invalied (return false) but I know you're not mean to return anything within the catch block correct?
What would you say is best, preempting an error by having a guard at the top or letting the error happen and catching it? I know it's swings and roundabouts really but it feels that if I know the arguments might be null or empty, I should test for it first?
Is this better?:
public void ProcessPerson(Request arg)
{
try
{
if(Class2.ValidateUser(arg.Username, arg.Role)
{
}
else
{
}
}
catch(Exception ex)
{
}
}
public static bool ValidateUser(string Username, string Role)
{
using(MyClass myClass = new MyClass())
{
if(myClass.GetAdmin(Username, Role)
return true;
else
return false;
}
}
public bool GetAdmin(string Username, string Role)
{
try
{
if (String.IsNullOrWhiteSpace(UserName) || String.IsNullOrWhiteSpace(Role))
throw new ArgumentException("Username/Role cannot be empty or null");
using(MyClassAdapter myClassAdapter = new MyClassAdapter())
{
myClassAdapter.GetAdmin(Username, Role);
}
return true;
}
catch(ArgumentException ex)
{
}
catch(Exception ex)
{
}
return false;
}
If not, are you able to show me what would be best please?
Thanks a lot for your help.
modified on Wednesday, September 14, 2011 5:14 AM
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I don't think there's anything particularly wrong with returning from a catch. The rule of thumb is that (as Pete says below) you should catch an exception where you intend to deal with it, and if you consider it dealt with you can return from the function. In this case, the calling code will not know that there was an exception in some lower layer. If you think the calling code should be informed, don't catch the exception and let the calling code deal with it.
What you've done in GetAdmin makes no sense. You're catching the exception you're throwing and doing nothing with it! Don't use exceptions to control the flow of code. If an empty or null user name/role is an error (i.e. in normal operation it should never happen), then throw the exception; if you want it to be valid input, but not an admin, then return false.
The only reason I was using "try { ... } catch { throw; }" was to make sure the original exception was passed on to the top calling method that would handle the exception and log where the exception occurred.
If you don't catch an exception, it automatically propagates up the stack. Handle it where it makes sense to do so, and once only. (Not always true, but generally you should not rethrow an exception.)
Since you included it originally I'm inclined to believe that the null or empty username is an error and GetAdmin, at least, should throw in that case. That means that, logically, it's invalid input to ValidateUser as well, I think, so I'd catch the error at the request level:
public void ProcessPerson(Request arg)
{
try
{
if(Class2.ValidateUser(arg.Username, arg.Role)
{
}
else
{
}
}
catch(Exception ex)
{
}
}
public static bool ValidateUser(string Username, string Role)
{
using(MyClass myClass = new MyClass())
{
return myClass.GetAdmin(Username, Role);
}
}
public bool GetAdmin(string Username, string Role)
{
if (String.IsNullOrWhiteSpace(UserName) || String.IsNullOrWhiteSpace(Role))
throw new ArgumentException("Username/Role cannot be empty or null");
using(MyClassAdapter myClassAdapter = new MyClassAdapter())
{
return myClassAdapter.GetAdmin(Username, Role);
}
}
It also seems like there are far too many layers involved in the authentication process. You have Class1 (which receives the request), Class2, MyClass and MyClassAdapter all involved in finding out this simple piece of information (whether a user/role combination is admin). What I typically do is at login time I populate a single UserInfo object which contains the role and user-specific access overrides, and then I can just authenticate like:
if(user != null && user.HasAccess(AccessTypes.Admin)) { ... }
(setting user to null if no user is logged in). HasAccess would look a bit like:
public bool HasAccess(AccessTypes access){
return access == access & (Access | role.Access & ~RemovedAccess);
}
I'm not sure if you can do that with enums but logically that is what AccessTypes would be, and UserInfo.Access, UserInfo.RemovedAccess and Role.Access would all be of that type. You might have to cast to int or uint to get the bit matching to work.
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To be honest, the catch statements in your ValidateUser and GetAdmin methods are completely redundant. In general, if you find yourself using catch/throw without doing anything in there, you have poor code. You should only catch exceptions if you plan to do something with them, e.g. reattempt to acquire a transient resource that you couldn't get and which triggered the exception.
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Thanks Pete.
Would my above post be any better? Or closer to better coding?
I'm just confused really, I think I've read too many articles on exceptions (or maybe not enough infact!). Some have said to deal with exceptions in the method that was called, others have said to let exceptions propagate to the top calling method.
(Or an alternative to the GetUser() function?)
public bool GetAdmin(string Username, string Role)
{
try
{
if (String.IsNullOrWhiteSpace(UserName) || String.IsNullOrWhiteSpace(Role))
{
LogEntry.New("Username/Role cannot be empty or null");
return false;
}
using(MyClassAdapter myClassAdapter = new MyClassAdapter())
{
myClassAdapter.GetAdmin(Username, Role);
}
return true;
}
catch(Exception ex)
{
}
return false;
}
modified on Wednesday, September 14, 2011 5:27 AM
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OK, the simple way to think of this is to only catch an exception at the point at which you intend to do something with it. In the case you have here, you are logging the fact that something went wrong, but does it make sense to allow processing to continue? That's the question you have to ask whenever you are attempting to place exception handling in your code.
For instance, suppose you have some code to write something over TCP, and there's a failure at one point which throws an exception, do you want to attempt to reacquire a connection or abort the processing of that message at that point? The answer to that question indicates whereabouts you want to place your exception handling - if you want to reacquire, you'd handle the exception at a lower level than you would if you just wanted to abort the whole thing and tell the user that there was a problem.
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Thanks Pete, your advice is really helpful.
Ideally when an error occurs I want to log what happened and exit. I guess I could just have one single Try/Catch block in the top calling function and catch either a custom exception and then the general Exception or maybe just the general exception? Would this be acceptable? It just doesn't seem like a clean exit, as opposed to returning false after catching an error, but that may be a misconception?
Thanks.
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