Wpf how does it work

And when does it get parsed? Does C call the parser? That is my question. So when the parser runs is not fixed. Why would you even care? I dont think they are CLR objects. They are not compiled to IL. More like CLR objects reading binary markup at runtime.

Source: blogs. Show 4 more comments. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming Net which would require more effort from the developer to implement both UI and behavior associated with it.

So it very easy to separate behavior from the designer code. With XAML, the programmers can work in parallel with the designers. The separation between a GUI and its behavior can allow us to easily change the look of a control by using styles and templates. WPF is a powerful framework to create Windows application. WPF - Overview Advertisements. Web Expand child menu Expand. Must Learn Expand child menu Expand. Big Data Expand child menu Expand. Live Project Expand child menu Expand.

AI Expand child menu Expand. Toggle Menu Close. Search for: Search. Modification and improvements in: Application model, binding, controls, documents, annotations, and 3-D Ul elements. Faster setup time and improved performance for Bitmap effects. New controls: Calendar. DataGrid, DatePicker. Multi-Touch and Manipulation. You can design very rich applications without coding or buying controls. Using data templates, a visual designer can easily define how a view model will be rendered or can modify its default visual representation without changing the underlying object itself or the behavior of the control that is used to display it.

Data templates can be thought of as views that do not have any code-behind. They are designed to bind to a specific view model type whenever one is required to be displayed in the UI.

At run time, the view, as defined by the data template, will be automatically instantiated and its data context set to the corresponding view model. In WPF, you can associate a data template with a view model type at the application level.

WPF will then automatically apply the data template to any view model objects of the specified type whenever they are displayed in the UI.

This is known as implicit data templating. The data template can be defined in-line with the control that uses it or in a resource dictionary outside the parent view and declaratively merged into the view's resource dictionary. The view model in the MVVM pattern encapsulates the presentation logic and data for the view.

It has no direct reference to the view or any knowledge about the view's specific implementation or type. The view model implements properties and commands to which the view can data bind and notifies the view of any state changes through change notification events. The properties and commands that the view model provides define the functionality to be offered by the UI, but the view determines how that functionality is to be rendered. The view model is responsible for coordinating the view's interaction with any model classes that are required.

Typically, there is a one-to many-relationship between the view model and the model classes. The view model may choose to expose model classes directly to the view so that controls in the view can data bind directly to them. In this case, the model classes will need to be designed to support data binding and the relevant change notification events.

For more information about this scenario, see the section, Data Binding , later in this topic. The view model may convert or manipulate model data so that it can be easily consumed by the view. The view model may define additional properties to specifically support the view; these properties would not normally be part of or cannot be added to the model.

For example, the view model may combine the value of two fields to make it easier for the view to present, or it may calculate the number of characters remaining for input for fields with a maximum length.

The view model may also implement data validation logic to ensure data consistency. The view model may also define logical states the view can use to provide visual changes in the UI. The view may define layout or styling changes that reflect the state of the view model.

For example, the view model may define a state that indicates that data is being submitted asynchronously to a web service. The view can display an animation during this state to provide visual feedback to the user.

Typically, the view model will define commands or actions that can be represented in the UI and that the user can invoke. A common example is when the view model provides a Submit command that allows the user submit data to a web service or to a data repository. The view may choose to represent that command with a button so that the user can click the button to submit the data. Typically, when the command becomes unavailable, its associated UI representation becomes disabled.

Commands provide a way to encapsulate user actions and to cleanly separate them from their visual representation in the UI. Note: View or View Model? Many times, determining where certain functionality should be implemented is not obvious. The general rule of thumb is: Anything concerned with the specific visual appearance of the UI on the screen and that could be re-styled later even if you are not currently planning to re-style it should go into the view; anything that is important to the logical behavior of the application should go into the view model.

In addition, because the view model should have no explicit knowledge of the specific visual elements in the view, code to programmatically manipulate visual elements within the view should reside in the view's code-behind or be encapsulated in a behavior. Similarly, code to retrieve or manipulate data items that are to be displayed in the view through data binding should reside in the view model. The model in the MVVM pattern encapsulates business logic and data. Business logic is defined as any application logic that is concerned with the retrieval and management of application data and for making sure that any business rules that ensure data consistency and validity are imposed.

To maximize re-use opportunities, models should not contain any use case—specific or user task—specific behavior or application logic. Typically, the model represents the client-side domain model for the application.

It can define data structures based on the application's data model and any supporting business and validation logic. The model may also include the code to support data access and caching, though typically a separate data repository or service is employed for this.

Often, the model and data access layer are generated as part of a data access or service strategy, such as the ADO. Typically, the model implements the facilities that make it easy to bind to the view. This usually means it supports property and collection changed notification through the INotifyPropertyChanged and INotifyCollectionChanged interfaces.

They also enable support for data validation and error reporting in the UI layer. Note: What if your model classes do not implement the required interfaces? In those cases, the view model may need to wrap the model objects and expose the required properties to the view. The values for these properties will be provided directly by the model objects. The view model will implement the required interfaces for the properties it exposes so that the view can easily data bind to them.

The MVVM pattern provides a clean separation between your application's user interface, its presentation logic, and its business logic and data by separating each into separate classes. Therefore, when you implement MVVM, it is important to factor in your application's code to the correct classes, as described in the previous section. Well-designed view, view model, and model classes will not only encapsulate the correct type of code and behavior; they will also be designed so that they can easily interact with each other via data binding, commands, and data validation interfaces.

The interactions between the view and its view model are perhaps the most important to consider, but the interactions between the model classes and the view model are also important. The following sections describe the various patterns for these interactions and describe how to design for them when implementing the MVVM pattern in your applications.

Data binding plays a very important role in the MVVM pattern. WPF provides powerful data binding capabilities. Your view model and ideally your model classes should be designed to support data binding so that they can take advantage of these capabilities.

Typically, this means that they must implement the correct interfaces. WPF data binding supports multiple data binding modes. With one-way data binding, UI controls can be bound to a view model so that they reflect the value of the underlying data when the display is rendered. Two-way data binding will also automatically update the underlying data when the user modifies it in the UI. To ensure that the UI is kept up to date when the data changes in the view model, it should implement the appropriate change notification interface.

If it defines properties that can be data bound, it should implement the INotifyPropertyChanged interface. Both of these interfaces define an event that is raised whenever the underlying data is changed. Any data bound controls will be automatically updated when these events are raised. In many cases, a view model will define properties that return objects and which, in turn, may define properties that return additional objects.

WPF data binding supports binding to nested properties via the Path property. Therefore, it is very common for a view's view model to return references to other view model or model classes. All view model and model classes accessible to the view should implement the INotifyPropertyChanged or INotifyCollectionChanged interfaces, as appropriate.

The following sections describe how to implement the required interfaces in order to support data binding within the MVVM pattern.

Implementing the INotifyPropertyChanged interface in your view model or model classes allows them to provide change notifications to any data-bound controls in the view when the underlying property value changes.

Implementing this interface is straightforward, as shown in the following code example. Implementing the INotifyPropertyChanged interface on many view model classes can be repetitive and error-prone because of the need to specify the property name in the event argument.

The Prism Library provides the BindableBase base class from which you can derive your view model classes that implements the INotifyPropertyChanged interface in a type-safe manner, as shown here. A derived view model class can raise the property change event in the setter by calling the SetProperty method.

The SetProperty method checks whether the backing field is different from the value being set. If different, the backing field is updated and the PropertyChanged event is raised. The following code example shows how to set the property and simultaneously signal the change of another property by using a lambda expression in the OnPropertyChanged method. This example comes from the Stock Trader RI.

The TransactionInfo and TickerSymbol properties are related.