Real Time Form Updating - Keep Single Threaded - Ongoing Maintenance
Dec 14, 2009
I have an app that I'm trying to keep single threaded, mostly for reasons to do with simplicity of ongoing maintenance. I've structured it so that I can eventually multi-thread it if need be but I'd rather not at this point. It's semi-real time and does perpetual looping to display a number of different graphs and do various work with both the graph display and the work being hosted in their own respective objects. If you're familiar with the Windows dispatch manager it's that general paradigm run synchronously. And yee haw, it pretty much works at this point and runs fast enough to meet requirements by a happy margin. I have a cosmetic problem that I'd like to solve if I could. When I left-click and move any form around, my graphs stop updating until I release the left click button. I was thinking about a doevents somewhere in the click event catalog.
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Jun 22, 2010
I have an Excel based algo-trading app that needs to take in lots of real-time data, and make trading decisions based on the calculations driven by the data. It is not one of those "read-only" stock ticker kinda spreadsheets.I created a COM object with VB.NET that runs in its own thread space which collects data from a socket, and when the data is read it raises an Event with data attached. In Excel VBA, the event handler parses the data, puts them to the right places on the spreadsheet to feed calculations (so far it sounds like a stock ticker app), and then, based on the results of the various calculations it does something.The problem is that when the user starts to click around the spreadsheet while there is large amount of data coming, the event handler's cell updating breaks apart. If the app is left alone without user action, it stands well. My frustration comes from not understanding what happens to the main thread when a user clicks around. Either the event handler blocks the user action, or the user action blocks the event handler (under which case I will put in some queuing facility). But I just don't see how user action can break the code (like causing VBA to stop executing)
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Nov 3, 2009
I've been a mangler of various types of code for a while now, I love doing PHP stuff but have found the need for some stand alone .exe stuff just recently and am using Microsoft Visual Basic 2008 express edition.Things have been going well so far with all my problems solved by Googling and since so many of the best solutions have come from here, I thought this would be a good place to come with this particular
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Apr 19, 2009
I started programming in VB2008 couple of weeks ago (I'm using the express version) and I'm getting stumped by this ridiculously simple problem. I am trying to retrieve varying parameters from an external application and display their values in real time on a windows form control e.g. a label or text box. I already know what class and methods to reference for that, however I can only display instantaneous values (unless I use a .click event handler, but thats foolish I want them displayed without my intervention) I tried writing a loop in form load event handler but that prevents the form from loading. I also tried a loop in another module but that doesn't work either.
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Apr 7, 2010
How can I display a running stopwatch on my form? I am creating a timer but I do not want to use the timer class.
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Oct 22, 2009
I'm using VB.NET. I want to build a large List (Of MyClassOrStructure) that becomes static after its initial population.I'm going to have multiple threads that need to iterate through this list to read data (no writing, inserting, or deleting)
Are there any very bad things that I need to keep an eye out for?
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Jan 28, 2009
After making the changes or adding a record I use invoke childmethod from my toolbar to call these subs. The first table updates and adds, but the second does not. I have set all of my textboxes databindings and double checked them. I get no error, but it does not update the second table. What am I doing wrong?
Public Sub AddRecord()
'Clear out the input data fields on a new Add.
ClearInputFields()
[code].....
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Jun 5, 2011
I'm having a small issue; I start a process and when that process exits, I raise an event which removes a control from my form.It all works perfectly until the part where I want to remove a control from my form. Visual Studio gives me a cross-thread exception even though I'm programming single threaded.
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Jan 28, 2011
how you display a live or current date and time on a Windows for application.
I am working with Visual Basic 2008(VS Studio 2008).
Example: January 28, 2011 8:00AM.
I have several books, strangely this subject is not properly covered.
This is my
Private Sub lblDisplayDateTime_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblDisplayDateTime.Click
Dim currentDateTime As Date = #8/2/2007 1:02:00 PM#
[Code]....
Finally, how do I make the time load when the form runs? I can't seem to find an event, that allows the time to display when I run the form. Currently, I have to click the area containing the label to get the time to display.
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Jul 24, 2009
I am trying to create a new thread that will import from an excel spreadsheet, because it was doing all the import before the form actually displayed to the screen. So the user never saw the form while it was importing..In the form's load event I create the thread and start it, but I get this large error:An error occurred creating the form. See Exception.InnerException for details. The error is: ActiveX control '8856f961-340a-11d0-a96b-00c04fd705a2' cannot be instantiated because the current thread is not in a single-threaded apartment.
I am using visual studio 2005 pro on Vista Business?
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May 24, 2010
Is there any open-source component for VB.NET that offers real-time spelling (i.e., as you type) much like word? I found some free and open source components but without that ability.
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Jun 15, 2011
I making a simple online chat using an ftp server by downloading and uploading text. I use a thread to update the chat log continuously. But it doesn't update in real time. Is there a way to create a server that clients can upload to and download from extremely quickly? How do programs like MSN messenger or better online multiplayer games do it?
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Nov 17, 2009
What would be the proper way to get the cursor position while the mousebutton is held down? I've tried using a do while loop with a background worker, but it freezes up the application.
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Jan 14, 2009
I'm working on a windows forms application (.NET 4.0).My form contains a 'Fast Line' chart using the Microsoft chart control included in VS2010.The chart gets filled with about 20,000 datapoints.My application then starts receiving market data from a server via DDE (Dynamic Data Exchange) in real-time and adds it the chart.
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Sep 19, 2010
I have to send a sequence of video frames over UDP as fast and real-time as possible and while I got the basics working, I am running into all sorts of difficulties. Some of my goals:Data will normally be sent over dial-up (hence UDP instead of TCP), but also needs to support fast Ethernet.It's OK to occasionally drop frames (hence UDP instead of TCP).Need low latency. The frame the remote receives should be one that was recently sent (no more than a few frames waiting in buffers).I need to be able to detect the effective bandwidth so that I can compress the frames more or less to keep frame rate up.I break up frame data into one or more datagrams of about 500 bytes and each has a sequence number and other info. The receiver reassembles the entire frame and detects if any datagrams are missing.If the receiver detects more than a certain percentage of dropped frames (e.g. 50% over the last 10 frames), I send a TCP message to the sender to slow down by 50%. Sender than slowly increases speed by 5% each subsequent frame.Using System.Net.Sockets.UdpClient to send and receive the data.I have a separate TCP channel used for control messages back to sender.My main difficulty right now is detecting the effective bandwidth and dealing with latency, especially over dial-up (max ~4,000 bytes/sec). For example, if I try to send 100,000 bytes/second using TcpClient.Send() they ALL seem to arrive (no dropped datagrams) but with large latency by the time last datagram arrives. I think the TcpClient.Send() function is blocking until the buffer is able to send which messes up my current algorithm.
Can anybody point me to any sources of information for how to:Detect actual bandwidth over UDP.A better algorithm for dynamically adjusting bandwidth to suit the available pipe.Send data smoothly at the desired bandwidth.A way to detect and keep latency down to a minimum.I have been spinning my wheels over the last week and every time I solve one problem it seems another rears up is head.
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Feb 22, 2011
Make real time chart?
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Apr 6, 2012
I created a form with MS Access with some dropdown menus and some check boxes. The main reason is for when the user select a check box or an option from the dropdown menu a specific phrase will appear on a Note box I created on the bottom of the form. Where I am having the problem is because I added a Text Box in Access where the user can type something in it. What I need is when something is typed inside of the text box the content should be mirrored inside of the Note Box on the bottom of the form. I was able to create the functions using VB for the dropdown menus and the check boxes but for the Free Form Text Box I dont know how to mirror the real time texting.
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Jan 11, 2012
are there any ways that i can extract my data from database and display it into my listbox in real-time? which means that whatever is updated in my database must immediately be inserted into the listbox without the need of refreshing or pressing any buttons. Immediate display.
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Jun 24, 2012
methods/procedures for sending real time data from a VB.net app to a web server (asp.net) for real time display. My question relates to the best method to send the data from the desktop app and the best way to receive and handle the data on the server. I'm not asking for sample code, just some idea of what methods to research. I am currently using a text file upload method but I'm sure there is a more efficient way of achieving this.
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Feb 12, 2009
I am converting an application to work with SQL.I need the application to monitor a specific table, so it can instantly pick up on changes.The sql server database is on the same machine.The table it needs to monitor is called MaintenanceRecords and it is inserted into via web service.I need to display a message in my VB project when an insert occurs in MaintenanceRecords table.
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Jul 30, 2010
It is possible to create a real-time application where 2 or more pc will operate on it, for e.g, a cinema ticketing system, when a seat is occupied, all the other machine will be updated in realtime accordingly.
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Oct 14, 2009
I work for a company that produces accident reconstruction software. We have a vehicle dynamics program that realistically simulates the motion of a vehicle (position and rotation of car and steer angle of individual wheels, etc).
All the positions of the car are stored into an array called AMTN. The vehicle dynamics program can calculate positions at time steps finer than .005 secs (200 FPS).
I need to represent this data in real time, and so far I have not been able to accomplish this. I have tried doing this in Excel/VBA, VB6, and am currently trying to do it in VB.NET.
I have used a whole plethora of timers and counters as well as different methods of drawing lines on graphics linked to images linked to picture boxes, etc. My animation program writes/clears the screen correctly, but there is clearly some sort of lag in either the timer or writing method. I have scaled it down to 25 FPS and there is still a lag.
Here is an example of what I am trying to do with each tick of the timer:
Code:
Sub Timer1_Tick1(ByVal sender As Object, ByVal e As System.EventArgs) Handles Timer1.Tick
MyGraphic.Clear(Color.White)
[Code].....
With each tick of the timer, the graphic is cleared, lines representing each side of the car are drawn onto the graphic, and the picturebox is then assigned to the image, which is linked to the graphic. This is just like how your asteroids program works.
Do I need to change my method? Should I use sprites? Or would it be better for me to create images/bitmaps of the animation beforehand and simply flip through them with a timer?
I'm thinking that creating the images beforehand might work because I do not have to calculate the vehicle's position as it is predetermined by my AMTN matrix.
if there is a more efficient way of displaying my vehicle on the screen that would allow for greater FPS, etc.
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Nov 2, 2009
I am having a problem trying to get a real time back from this code.
Code:
Public Sub Time()
Dim StartTime As TimeSpan = TimeSpan.Parse(txtStart.Text)
Dim EndTime As TimeSpan = TimeSpan.Parse(txtEnd.Text)
[Code]....
I am using a start time of 09:25 and an end time of 10:15 to test this with. I would like it to return 50, as 50 real world minutes went by. I am getting -1331385.
This is mostly someone else's code from a different forum. I have never used a TimeSpan method before and they keep telling me it works "like what I asked for".
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Dec 1, 2011
I'm wanting to do a real time graph, as a test i'm going to set up a timer to increment x and y values and then plot them every second on the graph.
I've got hold of Zedgraph, which is quite a nice add-in that i came across, does anyone have experience of doing this?
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Apr 11, 2011
i created a threaded form class that i call when i know an update is going to take a while....it is a simple form with a label and an animated marquee progress control. the code is listed at the bottom....whenever i try to set the message, it says i cant do it with error "{System.InvalidOperationException: Cross-thread operation not valid: Control 'MessageLabel' accessed from a thread other than the thread it was created on." from my form (in my SAVE function, i put the following line:[code]....
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Mar 13, 2009
I have made an application where I connect a VB.NET program to a PLC. I read and write to/from PLC variables.I would like any read value to be updated real time in my VB.NET program. Is there a good way of doing that? For now I update a variable by a button click.
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Apr 6, 2011
I recieved a gift recently visual studio 2010 ultimate a nice suprise I have been repairing and building PC's and networks for years working in local shops and buisnesses, but always wanted to learn programming so my GF purchased this for me nice suprise. So here is my beginner question. I am making a program that will take check info ( check number, amount, date and person or buisness wrote to). I have no plans on using it just trying to learn variable structures and arrays and thought this type of program was a good start. Now I would like to take the text of a text box in runtime and use that to input a new check number into the variable structure. Just so I am not confusing anyone I will write the basic code
[Code]....
So what I would like to do is use a textox labeled check number to add check numbers into the checkrecord structure instead of having to add them into the code manually is this possible?
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Apr 26, 2010
I've already wrote a simple program for connecting to a serial port that can send data to the microcontroller, do some basic arithmatic and transmit it back to my Form. This was just to see if I could set up the conection.I have a PIC Microcontroller giving an 8-bit number thats is taken from an external sensor device.What I want to do now is to present this data from the microcontroller in a textbox as a number either in real time (as the sensor output changes) or if not possible, on request (using a button).
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Mar 9, 2012
I'm using EF version 4.1, and would like to have the data from the database in realtime, i.e. if you open the application it detects if there is new data in the database, and update the above it! is It possible to do this? I am using EF 4.1 code first time
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Jun 5, 2012
i have a program that function as a DAQ System.i have input channel to gather information from sensors. The reading of each sensor such as voltage, current and temperature are displayed in the textbook. As we all know, DAQ system is involve taking data real-time measurement.My problem is:
1. how to update each row automatically as time goes on. the value in the textbook is updated by each second.Below figure shows how the excel can be written automatically row by row, as time ticking for a sec. this update will stop as the timer stop.
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