I have a WinForms application with some business objects which implement INotifyPropertyChanged and hook the PropertyChanged event via some controls & BindingSource on the form which raises an event back to my business objects layer...
There's just one issue - everything works fine, except only when the control loses focus. E.G., the user changes some text field, but he has to actually click on some other control somewhere BEFORE he hits the 'save' button (e.g. he has to cause focus on another control).
Is there a way to wire this up to OnClick or something so the change is propogated to my business objects layer as the user types the text (or even after he changed a drop down value) so I don't have to force the user to click on a different text box before he can save?
Googling has lead me nowhere but to examples on how to easily do this in WPF =(. But no WinForms examples...
Please Advise,
Drew
If you are using Binding class to connect object to UserControl, you may try to set binding's DataSourceUpdateMode to OnPropertyChanged.
Please, note that in this way you are writing data to your object before validation. This may be unsuitable for some tasks.
Related
I have my form with a menu bar and space underneath to display my controls. One of the buttons in my menu bar is suppose to be a print button that prints a graph that's currently in a User Control I display in the form. If the graph was on the form in the print button's eventhandler I could just simply call
graph.printing.print(true)
which isn't going to work in my case since the graph is in the control and not the form.
How do I communicate with a User Control from the containing form and access or pass its variables when needed? I also have a status bar on the bottom of the form which would also need to get updated from the User Control, but I'll be able to deal with that if I got help with just this one part. Please bear in mind, I also have another User Control I'm going to add to the form which will also contain a graph which will need the same treatment as the other graph on the first control when the print button is pressed. I plan on swapping these two out so I have one form displaying one control at a time.
I got this idea from this answer: https://stackoverflow.com/a/18191630/2567273 but after further research I can't find anyone asking about the actual communication process between a form and the control it contains.
I think this answer is close to what I'm looking for, but I think it's leading me down the path to using panels instead of User Controls.
After typing this I noticed the closest answer to my question may be this, but that question has the child raising events and the parent responding while I have the parent raising the event and the parent has to get information from the child.
One way to think about this is Roles. Presumably you built this UserControl to handle the management of the data related to the graphs. As such you can think of them in the Role of a Graphs Specialist . Once you do that, printing them is actually just one more thing it should perhaps do.
The form on the other hand, is not special just because it happens to get receive the command from the user to print. Its role in this might simply to be to know which usercontrol to contact and which method to invoke:
Sub PrintGraphMenuClick....
Select Case something ' determinant as to which UC to contact
Case operation.Foo
ucFoo.PrintGraph
Case operation.Bar
ucBar.PrintGraph
Other menu options like Clear, NewGraph, Save and whatever else there is somewhat the same way. The Form's Role here may be to receive the command from the user and pass it along to the right control, invoking the correct right method and passing the correct parameters - that is not a trivial task.
Of course, rather than a MainMenu, the usercontols could alternatively implement a ContextMenu and even receive those commands directly.
Very often offloading an operation to something else results in so many properties, filenames, streams etc having to be moved from here to there that it becomes burdensome. In this case it is not like the MainForm has some special ability regarding printers that the UserControl cannot handle.
There is only one right solution:
1) Add an event to your user control.
2) Raise the event when the particular "thing" happens in the user control.
3) Attach a handler to the event in Form code.
4) Add code to update the bottom bar in the event handler.
The idea is that I would have a set of forms, users would click through a "forward" and "back" button, and the current form would change to a different one. My issue is that I can write code that just pops up a new form, but im not sure how to do a "replacement" of my current form. How is this usually done?
What I did recently was to create a form with buttons already in place and a large panel to contain each step. The dialog would accept an initial step in the form of a IWizStep instance, and the things would roll from there.
Each step was a class exposing a UserControl responsible for the visual aspect of the step, while the logic itself was handled by the class (it was a little more complicated that that, but that was the general idea).
The IWizStep interface, implemented by the step and accepted by the dialog, was on the lines of:
Interface IWizStep
Event StateChanged As EventHandler
ReadOnly Property Control As Control
ReadOnly Property Title As String
ReadOnly Property CanMovePrevious As Boolean
ReadOnly Property CanMoveNext As Boolean
Function MovePrevious As IWizStep
Function MoveNext As IWizStep
End Interface
To put everything together, a controller class would know how to compose the steps necessary for each given action. Therefore I had a controller for, say, "Emit Order", which needed some 10 steps, and a controller for "Emit Orders in Batch", which needed only a couple of steps.
Create a set of UserControls, and add and remove them from a Panel in a single form. (and set Dock to Fill)
You could define a user control which acts as a "wizard". It just needs the buttons you have and an array of content panels, just have it switch through the panels when the buttons are pressed assuming a certain condition is met within the controls on the panel. There's no real definitive "wizard" maker, since it's pretty easy to roll your own wizard.
You don't need to do a "replacement" of your current form really, you could just add a new one to the project. If you do need to for whatever reason, just grab the control collection with Me.Controls, copy that somewhere, and put the new controls up. When you don't need the wizard, swap them out again. It's generally best practice to make a new form however!
All,
I have a TabControl in an application that started behaving strangely. Some background...
This program was converted from VB6 to VB .NET 2008, and used to refer to forms using their class names. In other words, I might have a form class called frmFoo. In the code for the program you might see:
frmFoo.Show()
or
frmFoo.UserDefinedProperty = True
During some recent changes, I created variables to represent instances of my forms much like these:
Public MyForm as frmFoo
MyForm = New frmFoo
MyForm.Show()
In doing so, I also removed code from the form's Load event handler and put it in the form's constructor.
When the form loads, or when a document is loaded and should influence the TabControl's selected index, something like the following will not necessarily fire the SelectedIndexChanged event.
MyForm.tbsForm.SelectedIndex = ValueReadFromFile
...or...
MyForm.tbsForm.Tabs(ValueReadFromFile).Select
Sorry to be so wordy, but there's more. If I open the form and look at the TabControl to verify that it's been set properly, everything works like it's supposed to. The misbehaving TabControl is contained within another TabControl, so I have to click the parent TabControl to see it. If I can see it, and run a test, the test always works. If I can't see it, and run a test, the first test I run will not fire the event. ...paging Dr. Heisenberg...
It's almost as if the control has to be initialized first by changing the value or making it visible onscreen...I'm totally lost on this one. It's the most unusual behavior I've ever seen. And everything worked perfectly before I began using variables to represent forms and placed the Load event code into the form constructors.
Can anyone help, or at least put me out of my misery?
SH
-------------------------------------------------------------- Edit #2
I just performed a test after having attempted to eliminate some of the variability in the behavior. But I wanted to confirm the previously-stated behavior.
I opened the program and read a file. This file contained a value that should have triggered the event handler. Without making the control visible, I can change the SelectedIndex property of the tab control without the event firing.
I closed the program down again, and reopened it. This time, selected the parent tab that allowed the child tab (the one whose event I'm concerned with) to become visible. I then selected a different tab in the parent control, meaning that the child control was no longer visible. When I opened the same file as before, it fired the event.
I'm tempted to implement a flag that confirms that the control has been repainted or whether the parent tab has been displayed. I may have to fire the event in code if the flag isn't set.
I want to reiterate that everything worked when the program referred to the forms by their class names and much of the arrangement of controls on the forms was done in the load event. Now the program creates variables and the arrangement of the controls is done in the form's constructor. I'm sure this has something to do with the problem I'm having, but I can't understand how. Any wisdom to share?
MyForm.tbsForm.SelectedIndexChanged = ValueReadFromFile
doesn't make a lot of sense. Is tha trying to assign a handler to the SelectedIndexChanged event? or is ValueReadFromFile the name of the tab?
What you're saying is that you have two tab controls, say, A and B. Tab control B is contained within a tab of A, and unless A has the tab page selected that contains the tab control B, the SelectedIndexChanged event of B will not fire if you change its tab programatically?
In which different ways have you tried to select a tab within the child tab control, and when is this code being executed?
I have a combobox that is populated by a database table I have. In my Load event for my form I have it populated by...
Me.BusinessTableAdapter.Fill(Me.BillingdbDataSet.Business)
My problem is whenever I "add", "edit", or "delete" a business I have stored I can't find a way to update the combobox I have. Whenever I exit and reopen my program and I can see the changes but was hoping someone could inform me on how to have it updated after a change has happened.
The problem is you need something that implements INotifyCollectionChanged.
MSDN
You can enumerate over any collection
that implements the IEnumerable
interface. However, to set up dynamic
bindings so that insertions or
deletions in the collection update the
UI automatically, the collection must
implement the INotifyCollectionChanged
interface. This interface exposes the
CollectionChanged event, an event that
should be raised whenever the
underlying collection changes.
You can refresh it manually, but the ideal situation is the bind to an observable collection class - http://msdn.microsoft.com/en-us/library/ms668604.aspx HTH
Wade
If you're using datasets you can use the dataview class which raises events when the underlying dataset is changed. Then you could either look into data binding them to the combo-box or write your own update code and put that in an event handler for the event raised when the list changes.
I have a tabcontrol that creates tab pages from a "User Control" I created (a separate form in vb.net) using this code: (MainTab is the separate user control I created which has text boxes etc in it)
Dim tmpTab As New MainTab
myTabControl.TabPages.Add()
Dim tmpTabCount As Integer = myTabControl.TabPages.Count
myTabControl.TabPages.Item(tmpTabCount - 1).Controls.Add(tmpTab)
myTabControl.TabPages.Item(tmpTabCount - 1).Text = "Untitled"
I'm using the devexpress xtratab control so the code might look a bit different than the default vb.net tab control.
Now in my MainTab user control file file, I can't for the life of me figure out how to call a control in the form1 where the xtra tab control is placed on. "Me.Parent.Dispose" works for closing the tab when executed via the MainTab control, but that's as far as I can get for communicating with the parent from.
Does anyone know the solution? I'm not sure if I have to reference something in the MainTab user control or what in order to communicate with any objects on the default form1.
Generally speaking, I avoid making my child controls cognizant of the parent. It leads to unpleasant coupling more often than I care for.
Consider adding a custom event to your MainTab class that your form can subscribe to. When you want to pass a message to the form, your user control can invoke the method, and your form's event handler can process it accordingly. This pattern helps keep your user control pluggable into other forms by reducing its dependency on its parent.
Creating a user control event in a windows form is discussed in this MSDN article:
http://msdn.microsoft.com/en-us/library/aa302342.aspx