Develop Reference

WPF monitoring property changes

I frequently have the following task:
I have a collection of objects (f.e. Customers) and want to provide the user with an editor for these objects. Typically I have some list control on the left side of the editor and a form on the right side. The form displays the properties of the object that is currently selected on the left side.
Regarding the confirmation of any changes, there are at least two strategies:
make the editor a modal dialog window and give it OK/Cancel buttons. On OK save all changes for all objects
give the editor a Save button above or below the form on the right side that would allow the user to confirm changes to the currently selected object.
My question is about the second strategy, implemented as an MVVM application with WPF:
I would like to give my user a feedback that there are unsaved changes. Applications like text editors often solve this by enabling the Save button when any changes occurred and disabling it again once the user pressed it to confirm her/his changes.
If I understand correctly I would have to monitor changes to any bound properties in my form (backed by a model class). Usually my model classes use auto properties (no explicit getters and setters). Do I have to write explicit getters for all my properties to enable the Save button when anything changed, or is there a smarter way to achieve this?

Following the MVVM pattern, your ViewModels should implement INotifyPropertyChanged interface, than you can easily subscribe to PropertyChanged event and monitor properties changes

If you don't want to write INPC aware getters and setters in your model classes, then another way is to write a equality compare method instead, and then have your save command availability callback call into that to compare the "live" object with the edited one. I'm assuming you have a cloned object that is being edited in order to rollback if the user chooses not to save.
WPF will call it automatically as the user clicks around and types, or you can give it a hint with CommandManager.InvalidateRequerySuggested()

Need to extend DataGridNumericalColumn for Telerik UWP

I have a need to create a custom version of the UWP DataGridNumericalColumn that allows customization of the RadNumericBox properties (ValueFormat, ButtonsVisibility, SmallChange, LargeChange, Value) as well as the ability to edit the value as cents (199) without decimal place while editing, but display as normal dollars with decimal cents (1.99) while not editing. I've tried two different approaches to extend existing controls, neither of which I can seem to get to work fully for me.
1) Tried deriving from DataGridNumericalColumn - impossible due to inaccessible internal members down the line, even with full source code from GitHub available.
2) Tried deriving from DataGridTemplateColumn - somewhat workable for initial display, but everything relating to inline edit mode vs display mode and validation message display on the cell seems beyond reach (not override-able) and I can't seem to use CellContentTemplateSelector to choose between the inline Edit mode RadNumericBox display and the normal TextBlock display because I can't seem to detect when Edit mode is applied to the cell.
It is starting to seem like the only way I can achieve what I need is to fork the GitHub code-base so I can derive from DataGridNumericalColumn with access to internal code.
What approach could I take to achieve my desired customizations?
(I am using Telerik UI For Universal Windows Platform, version 2017.1.301.45, at the time of this writing.)

I eventually worked out workarounds that let me get past the main difficulties in extending this functionality using the derive from DataGridTemplateColumn approach. Here are the updates and customizations I made - they are described mostly at the conceptual level, but it should be enough for others to duplicate this sort of customization for themselves.
UPDATE1:
An update as I've been working on this:
Continuing along with the approach of deriving from DataGridTemplateColumn, I found that I can successfully change my displayed markup for edit mode vs display mode by creating custom commands for editing operations in the grid (CustomBeginEditCommand, CustomCancelEditCommand, and CustomCommitEditCommand very similar to the ones in http://docs.telerik.com/devtools/universal-windows-platform/controls/raddatagrid/features/commands/editing-commands/datagrid-editingcommands-begineditcommand ) along with an interface IItemAwareOfEditMode, applied to the ViewModel items for the Grid's data, that has a single bool property IsInEditMode that I set to true or false appropriately in the custom commands, which is then used in a custom DataTemplateSelector to decide when to apply my edit markup vs my display markup. This uses (DataTemplate)XamlReader.LoadWithInitialTemplateValidation(editControlMarkup) for translating dynamically created markup strings to DataTemplates. For my implementation, I create the markup in a PropertyChangedCallback for my custom column's PropertyNameProperty dependency property.
However, I still am having issues with validation and displaying the validation messages, and reverting values when the user cancels edit. I have the ViewModel for the grid row items implemented such that they derive from ValidateViewModelBase, and so they add/remove errors appropriately according to the documentation on validation at http://docs.telerik.com/devtools/universal-windows-platform/controls/raddatagrid/features/validation . If I use the DataGridNumericalColumn (not customized) with the same data, the validation messages do appear pointing to the cell when the data is invalid, but with my custom column, HasErrors is true on the items, but the validation messages don't appear. Looking at the validation code in https://github.com/telerik/UI-For-UWP/blob/master/Controls/Grid/Grid.UWP/View/Columns/TypedColumns/DataGridTypedColumn.cs in the CreateEditorContainer function, it seems there is an EditRowHostPanel and ValidationControl involved along with the editor content, but I don't have access to pieces needed to implement the container exactly as is done there.
What can I do to get the validation messages to appear as they do in the DataGridNumericalColumn?
Also, what can I do to make cancelling an edit (clicking the blue X for the row when in edit mode) actually revert my custom column's value to what it was prior to entering edit mode?
UPDATE2:
Another update as I've been working on this:
Continuing along with the approach of deriving from DataGridTemplateColumn, I've managed to successfully display validation messages for the edit mode by including a ValidationControl in the edit mode template markup, which references the RadNumericBox from the template (by Name) using the ControlPeer property, and giving its DataItem property a value of "{Binding}", and appropriately populating its PropertyName.
This is getting close to what I need, but it seems that my CustomCancelEditCommand, which uses
Owner.CommandService.ExecuteDefaultCommand(CommandId.CancelEdit, context);
, does not appropriately update the display of the cell to its previous value. It correctly doesn't call the CustomCommitEditCommand when the inline row edit is cancelled; however, it displays as the modified value (not reverted to the value prior to edit). Even if you edit again, the value remains as the modified value when displayed in the grid.
I see that in https://github.com/telerik/UI-For-UWP/blob/master/Controls/Grid/Grid.UWP/View/Services/Commands/Editing/CancelEditCommand.cs in the Execute method, that it executes its base implementation, followed by
Owner.editService.CancelEdit(context.TriggerAction)
, which I don't understand (RadDataGrid does not contain a definition for editService and I can't derive from that CancelEditCommand class because it is internal).
What can I do to make cancelling an edit (clicking the blue X for the row when in edit mode) actually revert my custom column's value to what it was prior to entering edit mode?
UPDATE3:
I have finally managed an EXTENSIVE workaround that does revert my custom columns' value on cancel.
My workaround for the cancel functionality involved:
1) Created a CustomRadDataGrid, which derives from RadDataGrid.
2) Gave my CustomRadDataGrid class a CustomEditingService property, which is a CustomEditingService, which is copied and modified code from EditingService (mostly commenting out unneeded parts, but also changing InitializeEditOperation's implementation and changing CancelEdit to have an out parameter of the operation's OriginalValues dictionary), and which derives from CustomServiceBase<RadDataGrid>, which is copied and modified code from ServiceBase (changed IsOperational to return Owner.DataContext != null), which derives from CustomAttachableObject<T> where T : RadControl, which is copied code from AttachableObject.
3) Added GetActualValueForInstance function and SetActualValueForInstance method to my custom column, which uses reflection to get/set the data row instance's value for this column (based on using my PropertyName Dependency Property's value), and made the InitializeEditOperation of my CustomEditingService just save original values of my custom columns, and made the CancelEdit of my CustomEditingService return that dictionary of original values in an out variable.
4) Made my CustomBeginEditCommand call BeginEdit on the grid's CustomEditingService after calling Owner.CommandService.ExecuteDefaultCommand(CommandId.BeginEdit, context) - that allows my custom column original values to be stored.
5) Made my CustomCommitEditCommand call CommitEdit on the grid's CustomEditingService after calling Owner.CommandService.ExecuteDefaultCommand(CommandId.CommitEdit, context) - that allows my custom editing service to properly track its editing state.
6) Made my CustomCancelEditCommand call CancelEdit on the grid's CustomEditingService AND for each original value dictionary item, use the Key (column, as my custom column) SetActualValueForInstance passing in context.CellInfo.Item and the Value (previously stored original value), BEFORE calling Owner.CommandService.ExecuteDefaultCommand(CommandId.CancelEdit, context) - that restores my custom column original values prior to the standard cancel actions occurring.
Done! Whew... It seems that this library needs a lot of changes to allow for better extend-ability. This has been logged as a feature request at Telerik according to a reply to my support ticket with them on this subject.
I think other people will want to be able to extend Telerik's various DataGridColumn controls too, so I shared my struggle and (eventually) successful customization here.

Orchard Custom Form DropDownLists

After a bit of playing around with Orchards' Custom Forms module, i decided i wanted to use a dropdownlist to select a particular person with their email as the value for that selected option. While i was creating the form i couldn't see anyway you could set values to your options.
See below image for example:
Don't suppose anybody has come across this before or has a suggestion?

In your case I wouldn't worry about having different text and values for the fields. It's also potentially dangerous to make the recipient email an input of the HTML form.
The Custom Form Rule Event provided with Orchard gives you no way to look at the values of the content type created by the form. So, you're probably going to have to write your own. You should be able to base this on Orchard.CustomForms.Rules.CustomFormEvents.
Armed with this you'd be able to create new rules for each possible dropdown value and set the email address in the action for each rule.

How can I edit the properties of a button in a form, where the button is on a custom user control?

I have a custom user control, onto which I place a button control. I set the access modifier of the button to Public. When I drop the user control onto a form, I see the button, but am not able to select it or edit its properties in the form designer.
Ultimately, I want to create a far more complex custom wizard control, with a content panel, "Back" and "Next" buttons, etc. I have successfully created a content panel to which controls can be dropped into at design time on the main form.
However, I am bulked at not being able to edit nested controls on the user control itself.
When inheriting from a user control, or inheriting from a form, one can typically edit properties of controls whose access modifier is set to "Protected".
What do I need to do to be able to access controls of the custom user control from the designer of the form?

I think you need go to the user control designer view to modify the properties of the button (instead of the form where the user control is placed), since it is nested in the user control.

You can make basic changes to a child control of a user control on a form to the limited extent that you can expose the properties of interest via the parent user control designer and support the property changes at design time. You can make much more complex design time behaviors by writing your own custom designers but that is a potentially difficult to very difficult undertaking.
There is a good reason why it does not work the way you probably think it could and should and if you think about it carefully enough for a while, you will understand why. When you inherit from an object, yes you can change properties etc, but in this case you are creating a new type, so you can modify, add, redefine properties.
But when you drop a user control on a form, you are not creating a new type. You are creating an instance of a type, the user control, that is already defined. To the extent you can modify properties, you are modifying state that must be preserved for that instance. State must not only be persisted, but user controls also often involve painting etc so state changes can also have complex behavioral effects and this is a potentially complicated requirement that cannot be completely generalized.
So there are some modifications that are not possible at all, because they imply modifying the type, and you already have a type, you are only creating an instance. For the rest of the possible range of modifications that are ultimately state based, the platform only supports so much of the total possible state management.

bind object to textbox c#

I'm new to c# and I'm looking for a way to bind a property of an object of my own to the value of a textbox in a regular form (reset the property of the object everytime the value of the input changes).
I have read some information and it seems that this can be done only for database objects. Can you give me additional information.

Assuming you mean Windows Forms textbox,
say
textBox.DataBindings.Add("Text", obj, "SomeProperty");
whenever you feel like binding it. Bindings are usually done in Form_Load event handler, if the object can be obtained at that time of course, and if there's no complex logic with different data sources.
Note that this will only work in one direction (changing TextBox will yield object property changes). To sync the other way round, the object must implement INotifyPropertyChanged interface.

If you want to persist the information between runs of the application (i.e. have it be saved when you close the app and re-appear when it opens), it's easiest to use the Windows Forms designer (I assume you are coding a WinForms app) to bind the value of the TextBox to an application setting. (This article on validation provides a screenshot similar to what you want.) (EDIT: Here is the exceptional article on the subject: Exploring Secrets of Persistent Application Settings. And here is a snippet page that I put together to discuss binding.)
This binding is automatically two-way, unlike the binding that #gaearon mentions. You just need to make sure that you save the settings (i.e. Properties.Settings.Default.Save()) before closing the application (e.g. as the event handler for the Form.Closing event).
If you need more clarification, leave a comment.