Is it possible to execute some sort of code to determine whether or not it's a good idea to call Invoke? I dunno what you would do once you'd found out you can't but it could be useful for detecting some dead locks (like the one I have a the moment).
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I've got the following code:
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The problem is that, when I call the "SetStatusBarText" sub from another thread, InvokeRequired is True (as it should be), but then my threads stall on the Me.Invoke statement - pausing execution shows them all just sitting there, not actually invoking anything.
I have a filesystewatcher object. On it`s event it runs a procedure which fills a treeview with a data. I had problems with treeview methods, but when I run them using invoke method everything is ok. But I still have one problem. When I load the form for the first time, everything works fine. But, when I then close the form (me.dispose, me.close), and load it once again, when Filesystemwathcer start the procedure i have an exception "invoke or begininvoke cannot be called on a control until the window handle has been created" trying to run a treeview.invoke method?
View 9 RepliesWhat is Platform Invoke Service (P/Invoke)?
View 1 RepliesWe have a UI with a progressbar. I know how to invoke, safely, the control from which it was not created from a thread. there are threads being processed in a threadpool, all of which calls an "agent" (which is a notifier to raise an event back to the UI to then increase the progressbar). an "agent" is set as a property in a State object, which is then passed into a method which will be executed on the ThreadPool. so, I invoke on the UI the method to update the progressbar, but the bar does not seem to update at all (screen frozen) and it takes a very very long time for it to execute. without threading, no problem.
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how do i create dll application in vb.net? how do i call a dll application from an exe application?
using VB.NET, is there sample code where an exe application invokes a dll appliction?
Public Class StateObject
Public workSocket As Socket = Nothing
Public Const BufferSize As Integer = 1024
Public buffer(BufferSize) As Byte
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I have the HTML Help Workshop, and I can create a .chm file. When I add the file's name as a help file in the Project Properties form, pressing F1 invokes I also have a help menu item (which has F1 as a shortcut key), but clicking on the item produces no response. When I created the help menu item, VB generated stub SUBs for mnuHelp_Click() and cmdHelp_Click(); what code do I add to the SUBs to bring up the help file?
View 1 RepliesAlright, all I want to do is submit a form on this website.The program is simple enough - automatically logs me into the site.For reference; the website is ( url.. )I know, the game is lame..
Anyway, I have already figured out how to fill in User/Pass fields.But I am having problems understanding how to access the Login button.It should be simple, but the button itself is not assigned a name at all.Here is the only information given on the button itself [code]...
I have written a class that handles my socket information, which means i need to raise events back to my form class using a delegate. But for some reason the following does not work: -
Public Class Form1
Private WithEvents objEthernet As Ethernet
Dim Eth As New Ethernet
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Both of the Disconnected and connected events fire and are working from my socket thread but when i call "CallPassData" i get the following error "Invoke or BeginInvoke cannot be called on a control until the window handle has been created"
Is there a one-stop shop for determining which .Net types/attributes to use, given a native type?
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Also, as a related aside, what's the most reliable place for looking up marshalling declarations for Win32 functions?
Private Delegate Sub SetControlValueCallBack(ByVal value As Integer)
View 3 RepliesI wish to check the hard drive space used in a folder on a hard drive. This will happen continuously as a service, so it will be calculating the space used for thousands of folders all the time. I know that this code can be done easily in dotnet, but it seems to take a really long time. Are there any APIs to do this more efficiently, or does the entire looping process have to occur to do this check?
View 3 RepliesHow would one invoke a readonly property?
ListView1.SelectedIndices.Count
I use this code to invoke a function from a string, which I build in my application:
Public Class Form1
Dim f As New Foo
Dim methodName As String
Dim result As Object
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1. On the main form a scanner class is instantiated that (in the scanner's constructor) sets the scanner settings (baud rate, parity, etc) and opens the scanner for use
2. A barcode is scanned (via a scanner connected to the device in a seral port) while on the main form
3. In the scanner class, the DataRecieved event gets the needed info from the scanned code.
4. Then that info is passed back to the main form to a method RunCommandCode (which takes the scanned info as an argument)
5. On the main form the RunCommandCode calls another method CommandCodeHandler, passing the scanned info again
6. In the CommandCodeHandler sub a method is called in a Utils class (SetSelectedTab), which interacts with the form itself (determines how many tabs exist on a tab control), which is the reason for the invoke in the first place
So, before I figured out I needed to use the Invoke method (and, more specifically, that the scanner was working in a different thread), I was getting an error in step 6 on the line that got the TabControl.TabPages.Count.
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I dont know how to invoke a cmd prompt from vb.net window. from the vb.net i have tp ping an ip adress of a system in the cmd prompt.
View 3 RepliesI am new to making events and I have read up on them to further my understanding of them, and I have come across a situation that I am stuck at. Currently I have a handful of classes (lets call them a childform) that are all inherited from a class that's a form (lets call it a parentform) with an event called UpdateData(). When these forms are created they are added into a hashtable of ParentForms then added into another form. I call on these forms through a method that returns the form from the hastable. [code]....
View 2 RepliesI've got a messagebox that pops up after so long and gives you a yes no choice, if the user clicks yes, I need it to invoke, or press the button named GetA. How do I do this?I tried Invoke(GetA) but that did not work!
View 4 RepliesI 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 am using VS2010 (VB) and I am trying to dynamically call a function in another assembly. From my research, I seem to be doing it correctly --- but appearenty not since I get a run time error. {apologies if the code does not come out formated -- the code block helper is not loading for me}Here is the proto type of the function I am calling.
Public Class PrintLabel
Public Function ProcessMany(ByVal listRequests As List(Of Request)) As Windows.Forms.DialogResult
End Function
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When I step through in debug mode all seems great until I hit the .Invoke() line. It is then I get a paremeter count error exception.
I'm trying to figure out if it is possible to instantiate and invoke a delegate by name, rather than explicitly. I think the code below explains it fairly well. I want to accept a function name and then instantiate the delegate based on that. In the example I use a select case, but I want to eliminate that and just use the methodName argument itself.
Private Delegate Sub myDelegate()
Private Sub myDelegate_Implementation1()
'Some code
End Sub
Private Sub myDelegate_Implementation2()
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I am implementing a custom iDispatchLLInvoke handler for VB.NET - some of this is working.So Far - I have been able to intercept and provide custom handling of simple functions and property calls - but I am stuck when I try to set a property and get an error "Invalid Pointer (Exception from HRESULT: 0x80004003 (E_Pointer))".
I am using the new .NET 4.0 ICustomQueryInterface to do this. In Summary - I intercept and provide my own implementation of iDispatch - I load the dispIDs on the first call - and return a the dispID for each call within GetIDsOfNames - this ID is than passed to Invoke where reflection is used to get the value and return the result.
When I attempt to set a property - a call is made to GetIDsofNames and I return a valid dispID - the application than crashes with the error above and no call is made to Invoke.As a result - I am assuming that the issue relates to my interface definition been wrong becase the code never get's back to .NET code - see below for this code:
<ComImport(), Guid("00020400-0000-0000-C000-000000000046"), InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)> _
Public Interface IDispatch
Sub GetTypeInfoCount(ByRef pctInfo
As UInt32)
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I have a Tcp Client which I created on an application form but now I would like to create a class for it.
My prob is that when I check for any incoming data, I used to start a new thread. When this new thread finds any incoming data, I call a sub which invokes the form and everything works smooth.
This is what I am talking about,[code...]
How would I be able to do the same from a class? Or I dont have to create a separate thread when using classes?
Alright, all I want to do is submit a form on this website.The program is simple enough - automatically logs me into the site.I know, the game is lame.. I enjoy it though xD
View 5 RepliesI understand that .NET is multi-threaded and that is a good thing, but I continually run into issues when I have a background worker for example that is updating some control on my form and I have to do:[code] My question is why is this not built into the framework - surely if I am trying to update a DataGridView it should be intelligent enough to know when the update is from another thread and it could do all the above itself?
View 3 RepliesI'm working with the DevExpress XtraGrid control.I have a routine that goes thru and adds all the controls on the current form dynamically, and launches on a seperate thread the routine for a given control to initialize it to the value that will be displayed to the end-user. Some of the controls are displaying calculated values, and take some time to return their values, so that's why we are doing it on a seperate thread.
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I'm using a similar snippet of code for any control properties that have to be updated, and all work fine. On the above code when the actual Invoke is called, it APPEARS that the thread just ends and never calls the delegate, and doesn't return to finish either.
What should be the VB signature for the unmanaged function void PopulateBSTR(BSTR outstring)?The function PopulateBSTR does a SysAllocString and populates the string. Note the unmanagaed signature has the argument BSTR and not BSTR*. I can marshal the BSTR string using IntPtr signature when the C++ signature has BSTR* as the argument.
(The unmanaged code is an external dll which I cannot modify but I need to use.)
I've created a MyFunc extension (in Module Extensions) for all the base types as well as generic arrays, ICollection(Of T) and Dictionary(Of String,T):
Function MyFunc(Of T)(a() As T) As String
Function MyFunc(Of T)(collection As ICollection(Of T)) As String
Function MyFunc(Of T)(dict As Dictionary(Of String,T)) As String
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My question involves async operations in VB .NET. Given the following:
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