SyncLock Required Before If Statement Or For Loop?
Oct 2, 2009
If completedOrders.Count <> 0 Then
For i = 0 To completedOrders.Count - 1
SyncLock completedOrders
'Do some work, for example this:
Dim text As String = completedOrders(0).getCN & " " & completedOrders(0).getDeviceName & " "
End SyncLock
Next
End If
Is a synclock needed before the if statement or for loop? In other words. When you call methods like .length or .count is it necessary to synclock them or can another thread be writing to it at the same time. CompletedOrders is a generic list of a class.
I wonder how to use statement handles exceptions?Do I need to wrap the using statements with a Try/Cath/Finally clause in order to be sure that the SqlConnection object is closed and disposed even if the containing code throws an exception? [code]
My app is a fairly simple and im sure with the right knowledge this would take 2 minutes.. but sadly iv been at it for hours. So my scenario here is a huge network with 20+ file servers all with data spread out across them it can take hours to find the folder required.
Hence this app.. so it consist of a input box, progress bar and a button, using FileSystemObject I plan to interrogate a directory to see if a folder exists (folder specified by user input) however it need to check multiple directories, in my old app I used a list box which wrote to a text file allowing the user to add additional directories then using if statements proceeded through the servers.. however they have added that much that my IF's have ran out really because i know it should have been a loop
Imports System Imports System.IO Public Class Frm_main Private Const FILE_NAME As String = "C:directories.txt" Dim objReader As New System.IO.StreamReader(FILE_NAME) Dim Lines() As String = IO.File.ReadAllLines(FILE_NAME) Dim Dir As String
I am trying to understand how a for each loop works and am having some trouble. I am trying to create a program that will query a sql database, pull back the information and store it. I currently having it writing to a text file, and would like to take the information (such as name) and compare it to another list where the name is equal. However I am not exactly sure how the for each statement really works. I have looked at numerous sources and it doesn't make since to me as you can probably see from what I have put in here.
HTML Public Class Form1 Public Sub newarrest() Dim strsports As New System.Collections.Generic.List(Of String) Dim employeelastname As New System.Collections.Generic.List(Of String) Dim cnPodaci1 As New SqlConnection [Code] .....
I'm practising printing, and doing fairly well - not as hard as I was thinking.
My question is: is it better/preferable to use a "while..." loop instead of an "If..then" statement when printing.
All my printing code is in various If statements (if PgNbr = 2, If PgNbr = 3 etc) but I notice in most of the examples and webpages I read that a lot of printing is done in a "while..." loop
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click Dim s As New Staff
[Code]....
Basically I am trying to update each record with 2 random numbers each time the button was clicked,my problem now is, the system will update the record but the data was wrong. Example, by right all data should be different (randomly string) but for some row it was updated with same data but in randomly, something row1 row2 row3 has exactly same data for column 1 and 2 then row 3 has distinct data, second time, row1 row2 same data row3 ro4 with different data. It is in random sequence. When I add a MsgBox to do testing in the For loop the data was updated correctly with all different data.
i have 10 radio buttons that have yes/no values. These are options to one question, so need to in the database under 1 record. so - question1 yes, question 1 no, question1 yes and so on. i want to use a while loop or some other loop to take all these values and insert them or update them in the database for that particular question. i m new to programming. the db table is ID, question, Answer. so it will be 1 question1 yes, 2 question1 yes, 3 question1 no.
I am having a few issues with a For loop statement, code below:
Dim y1 as integer = "12" Dim y2 as integer = "24" Dim y2a as integer
[Code]....
Problem i have is that it selects all records that have a value equal to or less than 24 rather than the records that have a value greater than 12 and equal or less than 24. This appears to be an error i am making in the use of greater and less than?
I am currently teaching myself the caveman code of Visual Basic (VB.net). Apparently I fail at If-statements or something, because I cannot get this to work...
Is it possible to define my list of strings like in 'good old' VB60, to use only on ebyte of memory for each character? .NET always seems to store any string as unicode, which doubles the required memory. The case is that I have a huge list of strings, all of the same size. It is about 50.000.000 items, 12 characters each. You can imagine I am running out of memory in no time. I tried converting them to arrays-of-bytes but in that case I loose the possibility to perform a "LIKE" statement in a FOR-EACH loop to check for a specific item.
[code] The problem in my case, this is not working with this code. All I need are random numbers outside the above boundaries.Please note when I remove 'Not' in 'Loop While' statement, the programme runs indefinitely!!
I am trying to create a program in vbfor this problem: "A TV set is purchased with a loan of $563 to be paid off with 5 monthly payments of $116. The interest rate is 1 percent month. Display a table giving the balance on the loan at the end of each month". It must have 1 button and a list box that displays successive balances, contains loops to balances, loop code includes output to the list box, List box displays 2 columns (one for month and one for amount owed) and 5 months are displayed and the amount owed for each. The Amount Owed should go down each month from month 1 to month 5 where month 5 will equal to $0.00
Here is my code so far but somehow the 1 percent interest i cannot get to add on each month so I am not getting the write answer.
Code: Dim rate As Decimal Dim loan As Double Dim pay As Double
[CODE]...
I have attached a jpeg of what the end result should look like when code is being run.
I am having problem with the coding of this (endless loop) and formatting of summary boxes before tests are complete that should not happen. (the overall goals is to have a separate validation procedure that does not calculate or dat displays are not performed until after call function is complete and valid. The validation that takes place are that two boxes are filled in - one is text and the other is a numeric value. (using vb 2008)
I was just wondering if mixing SyncLock blocks and Monitor.Enter/Exit statements is dangerous. I know SyncLock uses Monitor and a Try block in the background, but are there any problems with using the two together for thread synchronization?
I am pretty new to multi-threading in general and I would like to know how can I lock a shared integer variable to not be accessed by other threads while it is read/updated by an other thread.When I try do do SyncLock myInteger, I get that error : Error 6 'SyncLock' operand cannot be of type 'Integer' because 'Integer' is not a reference type.
Here a simplified example of what I mean
Private Shared myInteger As Integer Private Sub MySub() SyncLock myInteger ' This does not work ' read/write a new value to myInteger End SyncLock End Sub
MySub is called by multiple instances of the class, and running in multiple threads?
Is there simple way to SyncLock an object that can be null? And before you ask for it, yes, I know that it isn't logical to perform a SyncLock on a null variable. However, that would simplify my code because right now, I have no choice but to perform a null check all over the place before calling a SyncLock.
I was wondering if this is known / expected behavior. By design?Is it documented somewhere?
My 'real' code does need something to keep one thread from accessing a listview while another is busy clearing and refreshing the Items collection, so it's not as easy as omitting the synclock section in the example below (The SyncLock in my case is on the ListView).
This code, which can be pasted over a new empty form's user code class, deadlocks during the Invoke call. It doesn't reach the entry point of SetText (setting a brakpoint there, the deadlock occurs before the breakpoint is hit).[cod]e...
I have an application that requires several threads, otherwise the main UI thread would end up frozen.i am after a little advice as i have not really don alot of threaded applications.
First Question;
I have a thread which handles data coming in from the serial port( this wil become much more complicated), is it safe to use a synclock on the serialport object : -
Suppose I have a byte array, Private Data as Byte(). This array is private within a class. The class provides public functions for reading and writing to Data. This class can be accessed by multiple threads, so I want to avoid a situation where reading from it and writing from it don't happen at the same time.
For now, I am using SyncLock to avoid issues. Can I put SyncLock Data in just the write functions, or does it need to be in the read functions? Or, both? I don't have a specific code example in mind. I am just curious if there is any benefit to locking for both read and write functions if the writing functions' SyncLock will make writing have exclusive access to it in the first place.
I'm trying to SyncLock my DataTable, to avoid problems with multithreading and stuff. But it doesn't seems to work. I'm trying to lock a DataTable wich is acceseed inside a nested for-loop:
vb.net SyncLock radiolopere For Each row As DataRowView In tableview
