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What is the exact error message, and where is it generated?
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Hi Richard
The error is, "Access to com port denied". as it is very hard to debug it but it happens on Open port call. I have done some changes, leave com port assigned and only remove or add SerialDataRceivedEventHandler. I feel it is still not the good way, but is working.
regards John
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You have a "number of forms", and imply that each form is opening and closing the port on activation / deactivation. I maintain the serial port should not be dependent on "forms"; and should be part of the app's start and stop process (and "interval" / wait processing).
The port should be "wrapped" in such a way that it can be shared by the various forms / processes.
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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Hi Garry
thanks for your reply. As I was unable to find some example, this is how I have created. I feel it is not good way, as I done it, as there is a lot of areas which is unpredictable. I will try to see. what I can do. If you have some link to give me some link to example, will be very much appreciated. I fully agree with Napoleon and like the internet and Code Project, to learn.
thanks for great help.
Regards John
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thank you Gerry
regards John
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assume you have a simple working social network (I wrote one as an experiment):
nodes are class Person ... identity properties
edges are class Edge ... FromNode, ToNode, Intensity (nullable double): they are one way following standard graph conventions.
both and Node have CRUD methods in place ... working.
if Intensity value is null: it means FromNode to ToNode has no connection
when Intensity's value changes: it raises a PropertyChanging ... the change can be canceled Iimplemented, working)
problem scenario:
an Edge Joe has a ToNode Mary and Intensity 50.
an Edge Mary has a ToNode Joe and Intensity 50
Joe's Node changes Intensity to 100 and raises PropertyChanging which Joe subscribes Mary to.
You see the possibility of runaway recursion if both Edges subscribe PropertyChanging to each other.
how to limit recursion ?
how to limit recursion when an Edge Intensity wants to raise raises PropertyChanging when a certain magnitude of change occurs ?
keep a count ? enforce a limit ?
appreciate your thoughts !
«The mind is not a vessel to be filled but a fire to be kindled» Plutarch
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BillWoodruff wrote: You see the possibility of runaway recursion if both Edges subscribe PropertyChanging to each other.
If they also change their Intensity in response to that event, sure. (if something else then I don't know what you mean)
BillWoodruff wrote: keep a count ? enforce a limit ?
Sure, I guess? But where do you keep that count and whose responsibility is this etc, idk ultimately it seems like a bit of hack.
Reading between the lines, here's what I think is going on:
- You have some sparse matrix.
- You updated one entry in it.
- You need to run some algorithm to restore some property.
So here's my proposal: run that algorithm on the matrix. That doesn't sound it means anything, but it does. It means, forget imbuing the individual edges with agency (at least in this context). It's the matrix as a whole that has a property that you want to restore, and the algorithm works on the matrix as a whole (hopefully not every entry needs to be changed). There's no difficulty now in running a limited number of iterations of an incremental algorithm or anything of that nature. You can just do that, explicitly, in one place.
Such a zoomed-out view may also help when implementing other matrix-based graph algorithms such as eigenvector centrality or whatever (do social networks use that? I don't know what social networks actually do to be honest).
But I don't really know what you're doing, maybe none of this applies to your situation.
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Thanks, Harold !
I did not explain adequately.
Joe and Mary's Edges are reciprocal.
Joe changes the intensity value for Mary ... raises OnPropertyChanging.
Mary subscribes to Joe's OnPropertyChanging.
Joe's change calls Mary's OnPropertyChanging handler.
Based on Mary's intensity value and Joe's new value ... Mary changes her value and raises her OnPropertyChanging event that Joe subscribes to.
Then, you get runaway recursion, and stack overflow.
Right now, i am thinking of writing a ChangeManager class outside Edge.
cheers, bill
«The mind is not a vessel to be filled but a fire to be kindled» Plutarch
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This sounds exactly like a good case for making the matrix responsible for the reciprocity invariant.
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Or just call "OnPropertyChanged", without a name, once, at the end of the "update" cycle. The binding engine then simply refreshes all bound properties. The issue is that most don't benchmark "PropertyChanged" and "optimize" it when it makes no difference (due to a given scenario's low "frame rate"). Users do not perceive "lag" below 100ms.
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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note: i am using OnPropertyChanging here.
Gerry Schmitz wrote: The binding engine then simply refreshes all bound properties.
Source of this ?
Speed is the issue here: preventing runaway recursion is.
«The mind is not a vessel to be filled but a fire to be kindled» Plutarch
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Thanks, Harold,
What does "matrix" mean here ? How can you have "reciprocity" and "invariant."
i'm dense, and, light-headed, these daze 
«The mind is not a vessel to be filled but a fire to be kindled» Plutarch
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Your data structure is really a sparse matrix, right? It's a bit hidden behind the domain-specific terminology, but in the end it's a weighted graph represented as a sparse matrix. There's nothing wrong with that, it's a standard way to manipulate weighted (and even unweighted) graphs in both programming and mathematics.
BillWoodruff wrote: How can you have "reciprocity" and "invariant."
Well I mean, there is some invariant on this matrix that you are maintaining, right? And it has something to do with the reciprocal edge (you called it that, I'm just going with it). If a weight somewhere is changed, then its "mirror image" (the reverse edge) needs to change in some way to restore that invariant. I didn't really get how it needs to be changed specifically (or what the invariant is that is being maintained by that change), but I suppose that's largely an implementation detail that doesn't need to affect the overall architecture.
So essentially my suggestion is: make the overall matrix responsible for maintaining that invariant, not the edges. And so, the edges would not try to "fix themselves" in response to an event, you would tell the matrix to change an edge weight and it would directly do so in a way that maintains the invariant (by changing the weight of an edge and the corresponding reverse edge), with no events involved (of course you can still raise them, but that wouldn't be the mechanism for maintaining the invariant).
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Thanks, Harold, okay ... for you sparse matrix; for me, node/edge Object graph.harold aptroot wrote: make the overall matrix responsible for maintaining that invariant, not the edges.
I'm going to implement that and see how it might work.
i hate the idea of removing and readding event handlers.
more ? in a while 
«The mind is not a vessel to be filled but a fire to be kindled» Plutarch
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This is the error I get when I try to run the sample app:
The reference assemblies for .NETFramework,Version=v4.0 were not found. To resolve this, install the Developer Pack (SDK/Targeting Pack) for this framework version or retarget your application. You can download .NET Framework Developer Packs at https://aka.ms/msbuild/developerpacks
I have downloaded and run "ndp481-devpack-enu.exe" from "dotnet.microsoft.com/en-us/download/visual-studio-sdks?cid=msbuild-developerpacks".
But I am new to C# so I may have done something wrong.
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If you got the code from an article, then there is a "Add a Comment or Question" button at the bottom of that article, which causes an email to be sent to the author. They are then alerted that you wish to speak to them.
Posting this here relies on them "dropping by" and realising it is for them - we have no idea what "sample app" you are referring to!
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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Member 16073627 wrote: The reference assemblies for .NETFramework,Version=v4.0 ...
ndp481-devpack-enu.exe
You have downloaded the developer pack for .NET Framework 4.8.1, whereas your error message says your project targets .NET Framework 4.0.0.
The page you've linked to doesn't provide a download for 4.0.0; this page[^] explains why:
Starting with Visual Studio 2022, Visual Studio no longer includes .NET Framework components for .NET Framework 4.0 - 4.5.1 because these versions are no longer supported. Visual Studio 2022 and later versions can't build apps that target .NET Framework 4.0 through .NET Framework 4.5.1. To continue building these apps, you can use Visual Studio 2019 or an earlier version.
According to this page[^], if you install VS2019 and select the ".NET 4 multi targeting pack" option, then you may be able to build .NET Framework 4.0 applications in VS2022. Otherwise, you'll need to stick with VS2019.
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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I am searching for a similar solution to the Zkteco project however it's for HikVision Biometrics devices.
Let me know if you are able to do this project we can set up a call to explain more.
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You're in the wrong place. This is not a "for hire" site.
If you want to hire someone for a project, try Freelancer.com, but keep in mind, you get what you pay for.
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I'm trying to save my list of numbers with a Zero to the left of the numbers <=9 and it's not having any effect,
I'm using the following code in Insert:
cmd.Parameters.AddWithValue("@_01", número._01.ToString("D2"));
I have the same code on Sql server and it works perfect,
would there be another way to do this in SqLite?
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Displaying leading zeros on a number is usually a UI presentation thing, not a database thing.
Is the SqlLite column a numeric one or is it a text column? If you're not actually verifying this right now, after you read this, you're guessing and that's bad for troubleshooting.
Leading zeros on a value will only work if the column type is NOT numeric. Like I said, this is usually something that should be handled by the UI, not in the database.
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@Dave Kreskowiak, Thank you very much for answering, it helped me a lot, a hug.
Where do I mark as resolved?
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You don't have to - forums here don't have a facility for that as they are discussion based rather than "Question / Answer". We have an area for those that has a "solved" indicator: Quick Answers[^]
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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