I have a form with several components, like TextBox and ComboBox, and I need to know when click in the out button if there was any changes in the form. Is there a way to do this?
You could create a generic change event handler which sets a flag on change, and then assign all the controls' Change events to it.
This could probably be done pretty easily by looping through all of your controls onload.
You could loop through all controls but this would have to be recursive because a control can contain controls, e.g. (no null checks for brevity):
private void IterateOverControls( Control parent )
{
ProcessControl( parent );
foreach( Control control in parent.Controls )
IterateOverControls( control );
}
In ProcessControl you could hook up event handlers to handle OnEnter (to store the state) and OnLeave (to check the current state against the stored state). You'd need to unhook all the event handlers when disposing. Also, the code to store check the state would have to change for different control types, e.g. TextBox would be the Text property, but a radio button would be an index, etc. Obviously this becomes simpler if you can compare form state to your underlying data store state, in which case you can just make the comparison on each OnLeave event.
One thing also to consider is do you need to track real changes? For example, I have 2 radio buttons: A and B. I check B (a change), so the out button or whatever has its Enabled property changes. I then click on A (i.e. back to my original state). Do you need to revert the button at that point?
This is why you should look towards a model view controller approach :)
The easiest way to do this would be to simply use a variable on the form named something like "IsChanged." Set it false when the form is initially displayed, and set it true if they make any changes.
Alternately, you could record the values of everything when the form is displayed, and when they finish, check the current values against the old ones to see if anything changed.
If this is already nearly finished, and you need something quick it's probably going to be easier to just always assume that something has changed, then in your update logic afterwards (whatever it's doing) don't update stuff that is still the same.
As someone else mentioned, it's very possible for someone to change something, then change it back. What would you want to do in that case? You won't be able to maintain a proper dirty state of the form without a fair bit of additional work.. this is something that you need to plan for before you start, really.
Related
I am currently developing a C# Windows Form Application.
I have a window with a table where you can edit some data and I would like to check if the user did something before to close the window. If he modified the data, we prompt a messagebox to ask him if he wants to save before closing the window. If he modified nothing or if he clicked on save button before we just close the window without any message.
As I start on C# I do not know if there is something to realize this. Maybe a kind of listener which detect any modifications and return a bool.
My save function returns a list with the data which have been modified, so I thought about call it and check if the list is empty or not. But It's maybe "heavy" to call the save function several times just to check is something changed.
Depends on what controls you have on the UI and how much flexible/dirty solution you need. One way is to capture change events (Text change, Cell Value change etc.) of different controls and keep a boolean flag to say something changed.
You may use Form.Closing event and to check in this event if you have any changes in your table. If so you can inform the user accordingly and proceed as per your application logic.
I'm writing a tabbed WinForms application that contains multiple DataGridView controls which are bound to BindingSources. The BindingSources, in turn, are bound to BindingLists of business objects. My business objects implement INotifyPropertyChanged.
My TabControl has three TabPages (A, B and C). If my user has made changes to the data in the DataGridView control on tab A and then tries to switch to tab B or C without committing the changes (in this case, writing the data to disk), I need to prompt them to save the changes or lose them.
In order to determine if changes have been made on a given tab, I created "pendingChange" variables for each tab. Each DataGridView control has it's own CellValidating event handler where I validate the data as the user makes changes. At the end of that event handler, if the change has passed all of the validation checks, I set the pendingChange variable for that tab to true. When my user clicks the button to write the changes back to disk, I reset the pendingChange variable. So anytime my user attempts to change to a different tab, I check this variable to determine if there are any changes that need to be saved first.
Now I've realized that a big flaw with this design is that the CellValidating event for the DataGridView control is fired every time a cell loses focus. So now I need to find a different way to track when a cell value has been changed. Is there another event that the DataGridView control exposes that would be better suited to this purpose? Or perhaps there's an event for the BindingList that would help me achieve this functionality? If I have to, I can add a boolean "modified" property to my business object and update that as required. If it's possible to avoid that, I would like to because one of the BindingLists contains 150,000 objects at any given time and iterating through that might not be terribly fast.
BindingSource has Events. E.g. CurrentChanged event occurs when the currently bound item changes.
I have a TabControl with two tabs. One tab has a list of stores and the other has a list of employees. On the store tab I have a button that displays all employees of the store; to do that, I want to switch to the other tab and invoke a showEmployeesFromStore(store_id store) method from that tab's User Control. How would I do that?
You've got the wrong mental model. Just because the user control isn't visible on the TabControl doesn't mean that the code is invisible as well. Just call the control's method in your code, it needs to be public of course. Then change the tab control's SelectedIndex property to switch the active tab page.
The button should not be part of the 1st user control. Actually it is better not to use a button but to just trigger an event when the user selects another store.
I would expose an event on the store user control for SelectedStoreChanged or something to that effect. Pass back the newly selected store_id in the event delegate.
Subscribe to that event with your form. When the event fires, it is the form's job to decide with to do with that information. In this case, have it pull out the store_id from the store UserControl's SelectedStoreChanged event and pass it in to EmployeeUserControl.showEmployeesFromStore(store_id store)
Keep your controls ignorant of each other. Let the owner of the controls decide how to react to whatever events are raised by the controls. You'll sleep better with dreams of increased usability, better separation of subject areas, and more fewer working weekends due to untangling odd control flow... ;o)
Just realized I missed a detail. The button you're talking about should be on the form itself and not any of the user controls, assuming you don't want it to just update in real time using eventing described above. On button click, the form should go check StoreUserControl.SelectedStoreID() and pass the result to EmployeeUserControl.showEmployeesFromStore()
I have a Windows form (.NET 3.5) that contains a propertygrid control. The propertygrid control gets refreshed periodically do display any changes that may have occurred in the class which it represents. I want the refresh to only occur if the user is not currently editing a property in the grid. Is there a way to detect if the user is currently editing a control?
Yes - it's a little hacky but you can find out which subcontrol of the property grid is active, and make an educated guess based on what it is. The following seems to work:
bool isEditing = (propertyGrid.ActiveControl.GetType().Name != "PropertyGridView");
There probably is, but might I recommend having your type implement INotifyPropertyChanged instead of refreshing the grid on a timer? This way you would never have to call Refresh yourself; the display would automatically update the value displayed for each property whenever that property changed.
Of course, if your type has tons of properties, or if you're using your grid to dynamically display objects of many different types, this suggestion may not be practical. It's just a thought.
This is a fairly complex problem. I'd suggest a two fold approach:
Keep track of the last time the changed events fire.
Keep track of whether or not the control has focus.
If the control hasn't been modified within a certain threshold and has focus, or if the control doesn't have focus, I'd consider that to be sufficient to determine that it is not currently being edited.
You could hook up the OnLostFocus event. This way, the control would only get updated once it no longer had focus.
protected virtual void OnLostFocus( EventArgs e)
In my project I have a settings form. Where if any changes happen I have to notify user about it if he wants to leave that page without saving his changes. At this time I am doing this by catching every control change event. I am sure there is a better way - like catching the change event from its container. Is it possible?
Rather than worrying about the controls directly, how about creating a Settings class that implements interfaces from System.ComponentModel like INotifyPropertyChanged and IDataErrorInfo and use data binding to get the values in and out of the controls.
Your Settings class can then not only record whether anything has changed but also make validation of the user input easier.
A good place to start is MSDN.
You have the right solution, but you may want to be very generic about catching the change events. For example, you could try something like this right after the InitializeComponent(); line in the constructor:
foreach(Control c in Controls) {
c.TextChanged += new EventHandler(genericTextBox_TextChanged);
}
genericTextBox_TextChanged would set a form-wide hasChanged flag to true, or something really basic like that. You may need to make this into a recursive function that loops through all of the children of c if it has child controls.
Let me offer you some kind of a workaround. My offer is to create a custom DataSet. Then add tables corresponding to the form controls. After this you can bind each form control to this dataset.Pros: You keep all the controls data-bound. So you don't need to care about the changing of particular control. You have just to control dataset changes. Cons (maybe): after this you should rewrite settings preview mechanism. Instead of changing controls you have to change data. IMO, it's not so hard, but I have no idea about this approach in your applicationI think this approach will be, at least, easy to debug.
If it's web, look at the unload event for javascript