heres the problem lets assume i have a label1 which its text is "(y+1)"i defined an integer, lets assume its x i made some operations up and lets say there can be diffrent results and i want to replace y with that math ops result and then define x as it writes in label1..
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How to use the signs "+", "-", "*", "/" as label text randomly. I am trying to create a math game for my kids. There I need a random sign to display every time they get new question to solve. I am able to display values [random numbers] but could not able to use this signs randomly as a single label text.
View 8 RepliesI get this error when i request the 'SelectedItem' property of a standard .NET ComboBox control from a BackgroundWorker control.
I know why this exception is raised, however, i thought that read-only operations to controls from different threads were safe?
I know i can turn this off using Form.CheckForIllegalCrossThreadCalls - but i want to make sure that readonly calls from non-ui threads are actually safe or not?
how to perform the database operation such reading data and using them for comparison within the VB programming..
Please guide me with explanation as i have very little knowledge regarding the database operation...
i am using VB.Net 2008 as frontend...and MS SQL Server 2008 (express edition ) as back end...
I'm trying to convert code from Delphi to .Net. I'm stuck on one line:
//Delphi code ss := Copy(ss, Length(ss), 1) + Copy(ss, 1,Length(ss) - 1); 'vb.net code ss = ss.Substring(0, ss.Length - 1) + ss.Substring(1, ss.Length - 1)
Delphi combines the two substrings, while .Net just concatenate them like a copy.
I reproduced the following code to update a database and I get the error" Operation must use a updateable query"
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I have a sub which is run in the threadpool with this command:
ThreadPool.QueueUserWorkItem(AddressOf UpdateStatus)And here's the sub:
Public Sub UpdateStatus(ByVal state As Object)
Dim ini As New INIAccess
If ini.INIRead(GetX_Games, "-1", "Patched", "0") = "1" Then
StatusLabel.Location = New System.Drawing.Point(120, 145)
StatusLabel.ForeColor = Color.Green
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How can I print a mathematical formula in a form? For a example I found in wikipedia a guide to do it in HTML: [url]
[URL]
But how can I do it in VB2008, showing the formula in a form?
Is there a method that allows me to evaluate a mathematical expression in a string? Example (Not actual Code):
Input = "2+2"
Output = SomeMethod(Input)
Output = 4
Update: Nevermind, I found a way around it by using DataTable.Compute.
i need mathematical calculation model code.
View 2 Repliesi got bored earlier so instead of doing my Maths homework i thought what the hell why dont i make a program to do it for me. The problem is im getting an error with my NCR function.For those of you who dont know NCR is used in calculating Statistics generally it goes like this
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What is the syntax for mathematical operations as SIN, COS and TAN in Visual Basic 2005?
View 1 RepliesI am getting some cross thread operations not valid when I am trying to run my code. I am handling a button click event to execute a method that runs a process to do a file converison, when the process is finished I run another method that converts the file to zip format, when that is done I run a method to upload the file to a ftp server, and when that is done I run one final method to update my database and the dataset; however, it is liking the way I am running these and I am getting cross thread errors and an overflow error when calling the fillBy method of my table adapter.
Here is the basic outline of what I have:
Private WithEvents conversionProc As New System.Diagnostics.Process
Inside the click event I call the method:
conversionProc.Start()
Then I handle the exit event of the Process as:
Private Sub conversionProc_Exited(ByVal sender As Object, ByVal e As System.EventArgs) Handles conversionProc.Exited
' Once the Process to convert has finished it will exit - Flag that we created the KML file
kmlCreated = True
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Let's say we have the following
Dim number1 as double = 2.24
Dim number2 as double = 12
Dim symbol as string = "-" (or "+" or "*" or "/")
How is it possible to execute this operation using the operator from the variable?
Im creating a server for a type of application on a mobile platform. When a user sends a message a sub in my server is called through WCF. Anyway from the sub that gets called when a user sends a message I add my ProccesMessage sub to a threadPool with the actual message as argument. In ProccesMessage sub I want to write the message to a log. I have Implemented this by directly writing the message to a log from the respective threads. Now since only me is testing this there is very little chance that 2 messages will arrive at the same time
View 5 RepliesHow to load file and save it as different filename? It saves almost twice the original size for some reason?
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim iFile As System.IO.File[code].....
Question 02:How to load it as numerical values?
Question 03:How to try applying an array of mathematical functions to the numerical values to see if size reduction is possible: I want to try testing all mathematical functions with any and all mathematical values of smaller size to see if the file can be compressed.
Is there a way to create new mathematical equations at runtime? Obviously you can pass new variables to a given equation, but I need to make a new equation altogether (then give it variables).
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I've got a program which starts with welcome screen "Enter the number of the random variables X" and this number refers to the columns. If it is entered 5 => a DataGridView will be created with 5 columns and 2 rows (first one is for random variable entered by the user, and the second is for probability). For example:I have to multiply x1 with probability p1, value x2 with probability p2, and so on. So EX = x1*p1 + x2*p2 +... Here comes the question - how to multiply and then add them?There are only 2 rows, that's how much I need :I've enabled only 2 rows, that's how much I must have for this program:
Const allowedRows As Integer = 2
Private Sub DataGridView1_UserAddedRow(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewRowEventArgs) Handles DataGridView1.UserAddedRow
[code].....
This is my way the dynamically generate a mathematical equation everytime the button is click. However, I want the combobox or the numericupdown turn disabled when the next question show out. For example, if the question N is generated, the combobox and numericupdown of question generated before N must be disable means that the user only can input to the current question but cant change the answer of the previous question?
Private Sub btnnext_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnnext.Click
If counter < 10 Then
Dim pnl As New Panel
pnl.Height = 40
pnl.BorderStyle = BorderStyle.FixedSingle
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I am using vb.net, and in my program I get this 'crossthread operation not valid' error when I run my backgroundworker that will make this textbox enabled true. My main sub will first turn the enabled to false, and when the backgroundworker runs it will turn it back true then exit. Why does it give me an error? FYI: There is more code to this but I don't want to make it any more confusing... Here is the stack trace:
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I've written my own program to assist other engineers with their work at my company. Some people have been able to install the program with no problems, others can't seem to get it installed and I'm having trouble figuring out why. They install .Net Framework 4 as this is the Target framework that was setup in the file, although I don't think I fully utilize all the features yet and not sure when I will. I will post the portion of the log that contains the error. If anyone decode some of this so I can track down the problem. I'm not sure if downgrading the necessary version of .Net would work or not, but didn't want to be changing that unless there was a good reason too.
PLATFORM VERSION INFO
ERROR SUMMARY
Below is a summary of the errors, details of these errors are listed later in the log.
* Activation of V:EAUsersRCFPE Files SetupPE Files.application resulted in exception. Following failure messages were detected:
+ Exception occurred loading manifest from file PE Files.exe: the manifest may not be valid or the file could not be opened.
+ Cannot load internal manifest from component file.
ERROR DETAILS
Following errors were detected during this operation.
CODE:
I'm getting a Cross-thread operation not valid error when my label text changes - this is very strange because it was working up until yesterday.The only way I can get this to work is by applying the invoke..[code]Is there a more simpler solution or will I have to invoke all my label coding?
View 9 RepliesThe error occurs at: For i As Integer = 0 To txt_load.Lines.Count - 1..The project exists of 2 rtb's. One with a list of lines. The other will be filled with the converted lines. The main reason that I use it is that I want to use the app during the conversion. The second is that I want to learn how this works.[code]
View 9 RepliesDuring Loading of form I call connectpaybox to show the list in the combobox, but after that it will result in the error "Operation is not valid due the current state of the object" but the combobox items that was taken from the database shows. I tried "select CAGECOST from CAGETYPE where CAGENAME like 'Normal'" where Normal is one of the items in cagename and it works.
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I am making a simple calculator that will evaluate functions I have a entry box and the user types in simple equations i.e. 1+4*3/5=? how would i make this evaluate the string?
View 7 Repliesi want to make a program in which the user can input a mathematical function so the program can then work with it. So the user would input something like x^4+x+2 and then an x and the program would calculate f(x). What i don't know is how to let the user input the function.
View 6 RepliesI am trying to get a better understanding of the uses of arrays in programing, and have been wondering why do programmers use an array when working with mathematical concept such as Fibonacci sequences? why are arrays so prevalent in coding now a days.
View 3 RepliesI know I'm not the only developer experiencing this issue but only within the last month I started receiving Visual Studio 2010 hangs while running running a simple ASPX web project within the IDE. On stopping the execution or closing the web page VS2010 hangs and becomes completely unusable - stating that VS is busy. It never returns and I have to stop the DEVENV process, resulting in a complete shutdown of VS.
Until now (1 1/2 years) I've been developing a Winforms application with no issues, other than VS2010 IDE errors that have been documented and I've been able to work around. Now, like my Web project, I am also experiencing the same hang but not as frequently. Other documented cases is this forum don't apply in this case since I'm not working with an IIS web site.
Additionally, in reading the forum messages I notice this issue has been around for years and has caused a great deal of grief and delay to many development projects. I'm running Win7 Pro, VS2010 pro on a Pentium Dual-Core CPU 2.20 Ghz with 4 GB memory laptop running in 32 bit mode. I'm very concerned at this stage of the process to upgrade to VS2010 SP1 since I've read too many horror stories online and can't take the risk of affecting the only support environment i have for Winforms application that is currently in production
I am trying my best to figure out how to go about this error i am reciving:Cross-thread operation not valid: Control 'ListView1' accessed from a thread other than the thread it was created on.
I have a backgroundworker thats extracting cells from an excel worksheet and placing them into the listview.
Upon form load i do this:Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Call createListView()
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Cross-thread operation not valid: Control 'ListView1' accessed from a thread other than the thread it was created on.I have a backgroundworker thats extracting cells from an excel worksheet and placing them into the listview.Upon form load i do this:
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Call createListView()
End Sub
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The error is on this line:
ListView1.Items.Add(lvi)