C# - Delegate Event To Form Without Creating Circular Reference
Jun 19, 2012
I have a class that is in an assembly due to being required for other projects that I'm currently working on. One class lets call it Class Factory, creates a group of controls which require click event handlers to be attached, I have algorithms which determine polymorphic behavior based on certain features but that is relatively irrelevant.
Due to the event handler having to open up a specific form that isn't part of my assembly, and that form requiring this "Factory" class. Without creating circular reference is there any way I can essentially "delegate" the handler event for the form to define? As a simple work around I have had to maintain two separate classes, one in the project with the form and one in the assembly.
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.Width = 1500
Dim panel As New Panel
panel.Location = New Point(0, 0)
panel.Size = New Size(1000, 200)
[Code] .....
View 2 Replies
ADVERTISEMENT
Jun 10, 2009
I have created a TextBox array where certain cells are assigned a number which I do not want the operator to change either intentionally or inadvertantly.The relevant TextBox cells are identified by their BackColor, (in this case LightBlue)If the cell is changed the original content is immediately assigned to the cell and a relevant message is displayed.My problem is that by changing the value back to its original value I create another TextChanged event and the consequence is that the MsgBox is displayed twice, one after the other.I have avoided the problem by not displaying a message box. The outward appearance is that the TextBox is not changed at all, which of course is my aim.However I would prefer to display a message box.An example of the scenario is shown below.
Another bewildering fact, (to me), is that in the example below, if the check is not made of the BackColor but instead the value of the TextBox the problem doesn't occur
Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
If TextBox1.BackColor = Color.LightBlue Then[code]...
In the example above, if in the Text_Changed event handler the 'Remark' is changed from one 'If' statement to the other the differences in the result can be seen.
View 3 Replies
Jan 31, 2010
Is it possible to create a circular visual basic form. I see plenty of tutorials on how to do this for VB6 but none on Visual Basic Express.
View 7 Replies
Sep 19, 2011
Iam maintaining a large code base I have inherited (ported from vb6 to C#.net 1.1, then to .net 2.0/c# and so on). I have this scenario.My main project references two DLLs - DLL-A and DLL-B
DLL-B references DLL-A. Both dll's and my main project are in 3 separate namespaces.
1) Are 2 copies of DLL-A being loaded in memory ? (dll ref count)
2) How do I find out how many copies of a .net dll is loaded in mem ? (which tool is normally used)
View 2 Replies
Sep 1, 2010
I've got a requirement where I need to calculate a value, however also refer to this value when calculating it. So I've got for example[code]...
I can see how this can be achieved in excel using Circular Reference, however I'm not sure how I go about it when using VB.Net. Is there a similar method to create a Circular Reference as in excel or any other way I can possibly work out the TotalValue?
View 5 Replies
Mar 26, 2010
How would you create and use a delegate to update the text of the main form from the DoWork event of a backgoundWorker?
View 4 Replies
Aug 22, 2010
I have multiple TcpClient connections to my program. The connections exist as instances of a UserConnection class, that fires events on logon attempt and when receiving messages. My program also holds a Users object, which is a list of a User class objects, holding saved data (username, password etc) for each user that is allowed to log in.
It seems convenient to put a reference object of the respective user, in the UserConnection class (when successful login is verified). Hence, when an event is raised by the connection, the connection object will hold the user reference. As any event handler logic will need to know which user is responsible for the event.
If I don't make a user reference in the UserConnection class, then I need to loop through the users (less than 20) each time, to find the correct user. Not a big deal maybe, but i'm looking to understand how it would be done by an experienced programmer.
When data needs to be sent to a user, I need to access a UserConnection object. Hence the User class also holds a reference to the UserConnection class.
View 3 Replies
Dec 21, 2009
I have an issue with a third-party COM+ DLL meant to be used from VB6, where it has a function to set a Callback for a hardware event. However, I'm using VB.NET, and AddressOf now returns a reference type instead of an integral type, which means that the setCallback function on the COM+ DLL apparently can't be used.
View 1 Replies
Aug 24, 2010
I have a small form that notifies the user on the completion of events (such as SMO restore). I want this form to appear from various sources (such as the below SMO Restore complete event) so I guess I need to create a new thread before creating the form? As it could be called from outside the UI thread. (I also need to pass a string to this form)
[Code]...
View 1 Replies
Jul 16, 2010
I am Creating a Lambda Expression, but it' not getting me the write Out put :
Public Class Form1
Delegate Function GetLastChar(ByVal S As String) As String
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[code]....
I want Send a Name like "Arindam" and its return me "m", the last character.but in messagbox return value shows "fasle" I can't under stand why it's showing "False" instead of "m", the last character.
View 3 Replies
Sep 16, 2009
may i know how to implement a delegate method into my project> currently i am using the serial port polling method by using a timer to read from the serial port, but now i am changing the method to delegate part.i have the code for the delegate part updating to the text box control but how do i modify it to update the mainform with my program codes.
The part for the delegate code is here
'---Event handler for the DataReceived event---
Private Sub DataReceived( _
ByVal sender As Object, _
ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) _
[code]....
View 5 Replies
Oct 9, 2010
So I'm using a Open Source DLL file.The DLL-file got a "Public Custom Event" named: Hashed and I don't really know how to use it.The example is as follow: (C# Language)
c.Hashed += delegate (object o, TorrentCreatorEventArgs e) {
Console.WriteLine("Current File is {0}% hashed", e.FileCompletion);
Console.WriteLine("Overall {0}% hashed", e.OverallCompletion);
Console.WriteLine("Total data to hash: {0}", e.OverallSize);
};
I've tried to convert it to VB.NET but it doesn't work.How can I get that code above working?
View 2 Replies
Jan 30, 2010
from the documentation we have this: Multicast Delegate: Represents a multicast delegate; that is, a delegate that can have more than one element in its invocation list.
so am i right to say that Multicast delegate is no different from a normal delegate other than the fact that it has arguments. so System.Action is a 'normal' delegate whereas System.Action(T)(Byval obj as T) is a multicast delegate?
View 5 Replies
Nov 5, 2010
In C#, I could do something like this:
EventHandler handler = this.SomeEvent;
...which would allow me to, for example, do:
Delegate[] attachedHandlers = handler.GetInvocationList();
In VB.NET, I can't seem to figure out how to do a similar thing.
This doesn't work:
Dim handler As EventHandler = Me.SomeEvent
...due to the following error:
Public Event SomeEvent(sender As
Object, e As EventArgs)' is an event,
and cannot be called directly. Use a
'RaiseEvent' statement to raise an
event.
But this doesn't work either: [Code] So how can I actually get an EventHandler from an event in VB.NET? The only idea that's immediately coming to mind is to use reflection, but that seems pretty ridiculous.
View 2 Replies
Jun 17, 2012
All the code i found for multi-threading is complex and not clear.What i want to do is creating a thread for reading and analyzing a big text file on Form_Load event, so that the form UI building continue without waiting for reading and analyzing the file finish.
View 2 Replies
Apr 12, 2012
I got this error when running my program. I wasn't like this before when I'm creating this program.
An error occurred creating the form.See Exception.InnerException for details. The error is: Object reference not set to an instance of an object.
[code]...
View 1 Replies
Apr 13, 2012
I'm having this problem with my code and cannot seem to get past it although it was working fine before. The error is "An error occurred creating the form. See Exception.InnerException for details. The error is: Object reference not set to an instance of an object." The code is:
CODE:
I am trying to get information to be pulled out of a database and show in text boxes on another form (frmviewsdets). The error occurs when it gets to the line frmviewsdets.txtsnumber.Text = rdr("StudentNumber") and even when a breakpoint is applied there it just moves on to the next and so on.
I have tried to show frmviewsdets before I pull the data out of the database beut I get the same message.
View 14 Replies
Sep 2, 2009
In C# adding event handler methods is very easy. You just type "object.event +=" and then press tab twice. Is there anything like this for VB projects? Note: This is for dynamically created controls or controls that are not declared WithEvents.
View 1 Replies
Feb 9, 2010
I've created a Delegate that I intend to call Async.
[Code]...
View 2 Replies
Jun 1, 2010
Code:
Public Class SendPings
Shared Sub New()
AddHandler Post.Saved, AddressOf Post_Saved[code].....
I get a error" Method 'Private Shared Sub Ping(item As BlogEngine.Core.IPublishable, itemUrl As System.Uri)' does not have a signature compatible with delegate 'Delegate Sub WaitCallback(state As Object)'.
View 4 Replies
Jan 28, 2012
I'm having problems with a program where I've got some multi threaded activities addressing the states of check boxes, which in turn are created by a user definable interface To achieve this I'm using the code below, which works on some occasions and crashes on other occasions when it stops with the following error NullReferenceException was unhandled Object reference not set to an instance of an object.Delegate Sub CBSetCallback(ByVal cb As CheckBox, ByVal value As Boolean)
Private Sub SetCheckBox(ByVal cb As CheckBox, ByVal state As Boolean)
If cb.InvokeRequired Then
Dim d As New CBSetCallback(AddressOf CBset)
Invoke(d, New Object() {cb, state})
[code].....
View 1 Replies
Apr 30, 2009
WTF, here's my code...
Public Class Form1
Dim BIT01 As Integer = BIT_01.Text
Dim Value As Integer = TB_OutPut.Text
[code].....
View 1 Replies
Sep 25, 2009
I have used delegates multiple times over the years but for some reason this very simple code isn't working:Form has one button and on textbox. Simply trying to update the textbox from another thread and although it looks fine it's not working.[code] the parameter is being passed to the DoSomething, the UpdateTextboxText is being run and gets the correct string. But the textbox itself remains blank and I'm stumped.
View 1 Replies
Mar 30, 2009
I am using VB.NET for Windows applications. What is the difference between Load event,Activate event and Enter event in the Form and in which order the above event is executed.
View 2 Replies
Dec 6, 2010
I have an app that basically monitors states, then when a state has changed, a notify form is triggered to show for the user.Timers are used on the form to showing a fading in/out of the form (somewhat like MS Outlook new email notification windows).I'm using a delegate from the main form to show the form, but when the first timer in the form is set to start, the timer's tick event is never ran. Everything up to that point in code works perfectly though.Is there something I need to do in order for the tick event to fire, like it would without the use of a delegate to show the form?[code]
View 2 Replies
Jul 23, 2010
I have the full path to a dll, but not a reference, where I need to instantiate an object that implements an interface that I've defined. I do have control over the other dll, so I am able to do things like stick a static function in the dll that returns the object I need. I'm just not sure how to call that function, or even if I'm approaching this right.
View 3 Replies
Aug 5, 2011
I am looking to create an order reference which is something like this
PLC0000001
Where the 1 would be my order id
but lets say it gets to 100 would like
PLC0000100
In VB.NET how could I build up a string like where i know i.e.
the starting part = PLC
Ending part = Order ID
middle = fill in 0's
View 2 Replies
Jun 18, 2009
Is there any particular reason why creating a reference to an object in an IEnumerable Linq query would be really slow? I have a Linq query list consisting of my own objects (count is about 200).I was doing a time-critical task, and this line (which was used a lot in a loop) took nearly a millisecond to execute:
Dim CurObject as MyClass = QueryResult(CurIndex)
View 2 Replies
Apr 13, 2011
I am working on creating an application (game) for a PocketPC with Visual Studio2005 in VB/.NET. I try to dynamically create a (new)button upon clicking a label and assigning certain properties to this button. For this I used below displayed code, but this button does not appear on 'Form1' - which is big enough to display it- but creates an error: A NullReferenceException. Such occurs when you try to reference an object in your code that does not exist, but I think I just did by using'..New..' Who can tell me what is wrong and how to fix this? [Code]
View 16 Replies
Feb 4, 2012
I have some different controls (PictureBox, Label,Button...) that are created by code. The set number of these controls isnot fixed. So let me set this number ton. And I have the following lines of code to create some of these controls.
For i5 As Integer = 0 To n
dBoxArray(i5) = New PictureBox 'PictureBox
Panel1.Controls.Add(dBoxArray(i5))
[code].....
View 7 Replies
