I do not know Why I am recieving a TimeOutException in my code:
Dim Uri2 As New Uri("http://localhost:8733/Design_Time_Addresses/ssWcfService/Service1/")
Dim binding2 As New WSDualHttpBinding()
Dim callback = New MyCallBackClient()
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I have a windows form that gets data from a scale via the serial port. Since I need the operator to be able to cancel the process I do the get data process on a second thread. The data collection process gets multiple readings from the scale one at a time. The form has a label that needs to be updated with information specific to each reading.
I call the method to get the data from the scale with this code.
Dim ad As New readALine(AddressOf thisScale.readALine)
Dim ac As New AsyncCallback(AddressOf Me.GetDataCallback)
Dim iar As IAsyncResult = ad.BeginInvoke("", ac, ad)
The delegate for the readALine method is defined in the UI code.
Delegate Function readALine(ByVal toSend As String) As String
The GetDataCallback method:
Private Sub GetDataCallback(ByVal ia As IAsyncResult)
.
.
.
lblInstructions.Text = _thisMeasure.dt.Rows(_currRow - 1).Item("cnt") & ":"
lblInstructions.Refresh()
.
.
.
End Sub
I get the exception on the "lblInstructions.Text =" statement. I thought the GetDataCallback method was part of the UI thread so don't understand why I'm getting the exception. I know this could probably be rewritten using a BackgroundWorker and it's appropriate events but for now would like to understand why this isn't working as expected. The application was written originally in VS2003 and just recently upgraded to VS2008.
I am an absolute beginner on ASP.net (VB.) Please pardon me if the question is too obvious for the experienced members.I tried to make a simple WebRequest in the async mode in case the target URL takes long to provide the data. In my code below, I just want to see if the callback block (RespCallback) is called correctly every time. If all goes well, lblResult should have the string '123' appended to it every time I click the button which calls the 'GetData' sub.
However, the lblResult only shows 123 after the first click. After the subsequent click, the lblResult only gets appended with '12', as if RespCallback is never called. When I tried to debug this in Visual Studio, the execution actually stepped right into the RespCallback part and the lblResult.Text watch actually shows '123123' but the resulting Web page always shows only '12312'
I am sure I am missing something basic here, but I just don't know what. I was even guessing that it has to do with browser cache (hence the result changes for the second time) but I don't know how to fix that either.
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I have the below code. What happens if the Upload method takes more than one minute for completion? Does the timer kick off another call to the Upload method immediately after one minute is over or Does it wait until the method finishes executing? I am implementing this as a windows service.
Protected Overrides Sub OnStart(ByVal args() As String)
Dim tmr As Timer = New Timer(New TimerCallback(AddressOf Upload), Nothing, 1000, 60000)
While Not tmr Is Nothing
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I keep getting the following data entry enty error : Data must be numeric. I can seem to figure out what the problems, for some reason I use CDec to display the output but the integer.parse looks good I believe. This is what I have done so far.
Public Class LibraryForm
'Declare variables.
Private AverageBooksDecimal As Decimal
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I have this SQL Statement:
de.SqlStatement = "SELECT A.Name, A.Catagory , COUNT(Patient_ID) AS PNO FROM PatientApplyToAssociation P INNER JOIN Association A on A.Association_ID = P.Association_ID WHERE A.Catagory='" & "health" & " '" & "' GROUP BY A.Name '"
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I have a form that is used at design-time to configure various properties. I've tried two ways to do a form-level catch all exception:
(1) I add a handler to Application.ThreadException in the constructor.
(2) I wrap the Show method, of the form, in a Try/Catch block
Both of these work at run-time when I test by adding a property grid to a form and set my component as the SelectedObject. However, at design-time the form simply closes with no message whatsoever; neither my message nor any message explaining that there is an unhandled exception. This is not about debugging at design-time. It's about how to present the user with a friendly message when my type editor encounters an unhandled exception.
When the form loadi set the format of datetime picker as "MMM yyyy" (custom Format) for only showing month and year.then i change the month using numeric key (pressing 2) so the month is Feb . again click the drop down of the Datetime Picker unhandled Exception occurs.because date is 31 and in feb only 28 days . For avoiding this i set the date as 01 as the value change .then the event occurs muliple times(recursively calling the value change event).
View 5 RepliesIm Building a auction application and i need to catch the exceptions i.e if two people press the bid button at the same time i need to capture that exception and figure out who was has the highest bidder out of the pair of them then show the relevant message, my question is how can i achieve the above?
View 2 RepliesBackground: I wrote code that will output all the currently logged in User's Active Directory group names. I want the group name (ex: Acomp_user_BIG) via IdentityReference.Translate instead of the current user's SID's (ex: S-1-5-32-544) returned via IdentityReference.Value.
Here is code that I used:
Public ReadOnly Property Groups As IdentityReferenceCollection
Get
Dim irc As IdentityReferenceCollection
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It is possible to catch an exception and throw a new exception which wraps the first exception as an inner exception: [URL] Also, if I call a function and it throws a certain error, but I catch it, will the calling code's catch handler execute? If so, and it is of a higher exception type, is this not wrapping the exception? eg I can throw exception ex of type IndexOutOfRange, log it but rethrow, catch a higher up exception and do something, or I can throw a new exception and wrap an inner exception like:
View 1 RepliesIn the following code I open several Excel workbooks from within the VS 2010 .IDE. I want to Try the open workbook code, then Catch exceptions using a dialogbox as a form created programmatically at run-time. The exception handler works, but the dialog box does not display in front of the workbook. So, the user can't respond to the modal form. If at that point the Excel workbook is shrunk manually to expose the dialogBox which is then dismissed, Excel pops up a "Save Changes?" alert and the VB code does not resume the Sub at the Me.Focus() line
When the workbook Is open Excel is the active application. I think this is why the dialog box is not in front, and I don't know how to solve the problem programmatically.[code]...
I'm having a problem with my DataGridView. When I double-click on any column, with exception to Date & Time, the grid advances by 1. As you can see the 2nd row is highlighted in blue, I actually double-clicked on the first one, under "Sent By." (See attached image)
Here is my code
VB.NET
Public Class frmPickAssignment
Dim dteStart As Date
Dim dteEnd As Date
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I'm trying to use a .DLL which Callbacks a Function of my project, but I can't get it to work.
Declaration from .h file of .DLL
void DLL_EXPORT SetEntity_CallBack(bool Active, _
void (*Entity_Callback)(int Site, int Application, int ID, _
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I have this code obtaining data from a sensor that is sending a string that contains 4 numbers separated by a tab and terminated by an end of line/ I am trying to use an asynchronous callback to get the data over TCP. That problem is that the callback function is not grabbing the complete string. Sometimes it will, other times it gets half in one retrieve and half in another. I need the callback to hold off until it gets a newline character.
Code:
Public Sub readVaisala()
Dim ip As String = "192.168.1.30"
Dim portNumber As Integer = 23
Dim time As Int32 = Now.Second * 1000 + Now.Millisecond
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I have a C++ dll that contains a callback. The callback has one parameter that is passed in and one parameter that is passed out. The parameter that is passed from C++ is a variant. So, we are going from a variant in C++ to an object in VB.NET. The function works. However, It seems that there is a memory leak on the VB.Net side. This must be a Marshaling issue. I have tried to use the MarshalAs Functions, but to no avail.
VB.NET
Declare
Function EnableWriteNotification
Lib
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there is error when i use callback function A callback was made on a garbage collected delegate of type 'skynet1!skynet1.Form1+myCallBack::Invoke'. This may cause application crashes, corruption and data loss. When passing delegates to unmanaged code, they must be kept alive by the managed application until it is guaranteed that they will never be called.
View 6 RepliesI am working on a Twitter application and with the authentication process, Twitter returns Two Tokens with a Callback URL, For example: [URL]. How do I extract each token and put them into separate strings?
View 5 RepliesI am writing classes in VB.Net (both managed). The main class "A" creates an instance of "B". Class "B" must call a method of Class "A". I need to know two things (syntax, etc...):
1. How does class "A" tell class "B" what method to call?
2. How does class "B" call the method?
The method must pass back an array of Shorts (in this particular example), either as a return value, or as a ByRef argument.I don't want to use an event if I don't have to. The execution is timing critical. (I assume event handling involves a lot of overhead by the operating system, but I may be wrong.)
I am a relative newcomer to Windows programming and VB.net. What we are trying to do is call a function in an existing, 3rd party COM dll. This function requires a callback parameter, whose type is an interface also defined in the dll.In our VB.net application, we have added the dll as a COM reference, and created a class that implements the interface in the DLL. We then send an object of that type as the callback parameter. This compiles fine. However, when we run the application, we receive an error stating that the program is unable to cast the object from our existing type to the interface type.
I suspect that there is a simple fix, but so far, my efforts to find a solution have come up short. If anyone could point me in the right direction,
I have a bunch of operations that need to be executed simultaneously. For this I'm using the thread pool to execute the tasks. I'd like to know if it's possible to consume some sort of Async Callback (similar to BackgroundWorker.DoWorkComplete) when each thread is finished. The reasoning behind this is that I have a windows service running that uses IPC to update a GUI and I need to know the time at which each specific thread finishes I've used background workers to do a set of tasks and they work perfectly, however, they take longer than I would like. I've timed the execution on my BGW method for a designated number of said tasks and it took 27 seconds, and the same set of tasks takes 4 seconds using the threadpool method. I've also tried using managed threads, to the same effect as the background workers.
View 5 RepliesI have a class with a mthod which does a a time consuming task. I know how to start the method in a separate thread using the Threading.Thread class. What I want to do is use callback so as to have the method report its result to another method when completed. I chose to use the asynchronous Begin/End call pattern.
Private Function BeginConnect(ByVal URl As String, ByVal callback As AsyncCallback, ByVal state As Object) As IAsyncResult
'Some Code
End Function
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Situation: i've created several forms with a datagrid:formwithdatagrid1formwithdatagrid2formwithdatagrid3.... These datagrid can be filled manually or with a selection list. I've written this selection list a a new form (frmSelectionList), witch is called with a SQL instruction, now this selectionlist calls a funtion in formwithdatagrid1 to return the selected value. Question:How can the same selectionform being used for all datagridforms?
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I'm trying to convert C++ API to VB.Net, but this function is too hard and i don't know how make it work.
Here is the API doc for this function:
void RemoteDllSetReceiver(void *inst, on_received_buffer_t received_buf_cb);
Sets a callback function to receive notifications from the DLL. The prototype of the callback is:
typedef bool (*on_received_buffer_t)(void* inst, const unsigned char *buffer, unsigned int size);
Where inst is the pointer originally passed to RemoteDllSetReceiver buffer & size contain the notification text as defined in the Remote Protocol. Note: notifications may arrive in different threads (e.g. network, timer, audio).
I can't imagine what i mus do with on_received_buffer_t, must it be a delegate? Like you can read, this functions returns notifications from the DLL like connection status, user id...
I've used the async classes in the .NET framework several times but I've never tried to do something like that myself - I mean I've used background threads and made them invoke other methods on the UI thread loads of times but they have always been hard coded method names, not something where you can specify what method is invoked when the background thread is finished.
I'm writing the data access layer for my current project and I want to have all of the methods be asynchronous, so these methods in the DAL need to be able to 'call back' any method that is specified, rather than a specific method in the same project as I would normally do. This is how I have done it, and it seems to work, but I'm not sure that this is the best way or even close... Here is the signature of public method in my DAL that my programs call:
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why my mciSendString callback isn't working?the app is a console app, with a nativeWindow msgHandler class.
here's the code:
Imports System.Windows.Forms
Public Class msgHandler
Inherits NativeWindow
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i'm using socket programming in vb.net 2005 and make a Server/Client windows application and it used in the network to multi user chat server and havent error and it work , but one BUG in server app : the Server app. work currently until the number of clients more than 30 and then it crashed . and error is "socket.exception" . now tell me what to do ??? it's very very important to me because the number of server's CRASH in on day more than 10 time and i end it and then run again and it's not good for my job .
View 5 RepliesI have a vb6 app, the error from event view is Faulting application vb6.exe, version 6.0.81.76, stamp 3592011f, faulting module vba6.dll, version 6.0.0.8169, stamp 358b0c74, debug? 0, fault address 0x0001982e. For more information, see Help and Support Center at [URL] And a message box pop out. Exception has been thrown by the target of an invocation. The code is
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I have been reading the async design patterns on MSDN and the general idea makes sense to me but in practice it is proving to be more difficult. I am working on a project utilizing VMWARE VIX.
HTML Code: [url]. Each function such as connecting to a host server, retrieving properties, etc. can be executed in two different ways.
Connecting to a host using a blocking Wait:
Code:
Dim m_lib As New VixLib
Dim m_hostJob As VixCOM.IJob
[CODE]...
Code:
Dim m_lib As New VixLib
Dim m_hostJob As VixCOM.IJob
dim m_callback as VixCOM.ICallback
[CODE]...
The problem with the VIX SDK is that sometimes the functions never return, hanging the application. dblock.
HTML Code:[URL] came up with a library that specifies a timeout value. When the timeout runs out the method aborts and returns regardless whether it finished or not.
The callback method is an active wait where the code continues to execute. What I want to implement is a blocking wait with a timeout. The ICallback interface has one sub OnVixEvent(IJob,Integer,IVixHandle). This method is fired at least twice, first when some progress is posted and second when it is complete. The first call to this method can be one second after registering the callback or 30 seconds, so I can not rely on this method to block the main thread. how to create some kind of async result class that would block the main thread from executing until either a timer runs out or the OnVixEvent method returns an Operation Complete signal that also implements ICallback.
I am creating a class ("Class B") which is used by another class ("Class A") which instantiates it in VB.NET 3.5.I would like Class B to read a value assigned to one of its properties by Class A every time an event happens in Class B.However, I would like this property value to be dynamically assigned to the property by Class A when the event is fired in Class B.I was thinking about somehow creating a delegate function in Class A that is linked to the property in Class B so that when the event is fired in Class B it would eventually invoke the delegate in Class A so that it returns a value to Class B.I've been reading around delegates (that's how I arrived at the idea), but I am stuck on how to code this up - could someone please help with some skeleton code?
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