WPF

XAML stands for Extensible Application Markup Language.It is used for developing the GUI of WPF applications.We can initialize objects using XAML.It can be used to easily create hierarchy of objects.

XAML allows to decouple the UI design from the WPF application logic.This means that UI designers and developers can work independently and later integrate the code and XAML UI easily.

We can create XAML by using the tools such as expression blend.

Following is a XAML GUI of WPF.There is Window defined in XAML.It contains Grid element.Grid is a layout control.

UI is developed by setting the attributes of the class represented as elements in XAML.In the above sample there is window element,grid element,stackpanel element and label element.The attributes of these elements are set to appropriate values.

 

Follow on:

There are mainly two types of templates in WPF:

• DataTemplate  Used to define the appearance of bound data.
• ControlTemplate   Used to define the appearance of the Control itself.

DataTemplate is used to define the appearance of displayed data. DataTemplate is defined using XAML.It describes the appearance of data.DataTemplate  can be applied to contentcontrol or itemscontrol.

When displaying values in a control such as ListBox ,it is straightforward to display property values.For example if you need to display the property called name in the ListBox then you can just use:

<ListBox ItemsSource="{Binding}" DisplayMemberPath="Name">
</ListBox>

This will display all the names of the bound object in the ListBox.

But if you want to display more complex information such as combination of properties for each ListBox item then you may need to use DataTemplate.

DataTemplate in WPF

Data templates are used with data binding ,when you want to render the bound objects in a specific way.It is derived from the class FrameworkTemplate.

Many controls in WPF have properties which are of type DataTemplate.For example ItemsControl have ItemTemplate property and DataGrid has RowDetailsTemplate property.

ItemsControl can display list of values.There are several items control in WPF.Some of the ItemsControl are ListBox and ComboBox.

ListBoxItem can display only a single field.To display a combination of fields you can use Data Tamplate.You use a ListBox control for binding to a list of items as:

<ListBox>
<ListBoxItem>ListBox Item</ListBoxItem>
</ListBox>

This will work if the type of ListBoxItem is string.For example if you have a list of Student names then you bind the list to the listbox as:

List<String> lstStudents = new List<String>{
"Marc", "John","Robin","Amit"};

you will get the values in the listbox as:

But if the type of ListBoxItem is object then you will not get the correct values in the listbox.

But if you bind a collection of objects to ListBox or other ItemsControl then the toString() method of the ItemsControl is called.If you set the ItemsSource property of the ItemsControl then you get the name of the objects in the list:

You will get the following List:

//Declare Student class

 class Student
        {
            public string Name { get; set; }
            public string RollNo { get; set; }
        }

//bind to List of Student objects
List<Student> lstStudents = new List<Student>{
new Student{Name= "Marc",RollNo="01"},
new Student{Name= "John",RollNo="01"},
new Student{Name= "Robin",RollNo="01"},
new Student{Name= "Amit",RollNo="01"
}
};
lstStudents.ItemsSource = lstStudents;

This is because you have not specified what each item in the list should display.In the absence of this information ListBox displays strings which represents the name of the objects in the source collection.

To display the fields defined in the objects of the list you use the DataTemplate.You can define the DataTemplate as:

<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Name}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>

Another use of DataTemplate is when you need to display combination of more than one property in the ListBox item.You can easily implement such scenario using DataTemplate as:

<ListBox.ItemTemplate> <DataTemplate>
 <StackPanel>
 <TextBlock Text="{Binding Name}" /> 
 ID:<TextBlock Text="{Binding Id}" /> 
</StackPanel>
 </DataTemplate>
 </ListBox.ItemTemplate>

 

Follow on:

Application class is the most important class responsible for managing the application level functionality.The life cycle of WPF application is managed by the Application class.

It manages functionality such as setting which window is currently active in the application,handling unhanded exceptions and defining resources to be shared across the application.

A running WPF application consists of a single object of Application class.It raises different events when the WPF application is executing.

• Run  method starts the application
• After the Run method is called it fires the StartUp event.This indicates that the application is starting.
• Activated is raised when the application starts executing
• Deactivated is raised when the application goes to background.

You can implement the following methods in your application class to handle the above events:

• OnStartup(StartupEventArgs)
• OnActivated(EventArgs)
• OnDeactivated(EventArgs)
• OnExit(ExitEventArgs)

You implement these methods in the code behind of your app.xaml file

public partial class App : Application
{

private void OnStartup(StartupEventArgs)(object sender, StartupEventArgs e)
{
//
}


private void OnActivated(object sender, StartupEventArgs e)
{
//
}
}

It also provides the Run() method which starts the application

app.Run();

You define application resources using the XAML of the application class as:

<Application x:Class="Application"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="MainWindow.xaml">
<Application.Resources>

</Application.Resources>
</Application>

The resources which you define in the XAML of the application class can be accessed across the entire application.

Follow on:

Dependency property is just a normal CLR property with extra features added.Some of these features are related to:

• Animation
• Data binding
• Styles

There could be a hierarchy of data sources for dependency property.The value of dependency property is calculated based on the data source with highest priority.For example animation data source has higher priority then data binding.

Dependency property are used just like a normal CLR property.Most of the properties defined by WPF elements such
as TextBox ,Label and other controls are dependency properties.If the normal CLR property doesn’t meet your requirements then you can define a dependency property by following the below steps:

1.Declare a class which will define the dependency property

public class SimpleDependencyClass
{

}

2. Declare a static readonly field of type DependencyProperty.

public class SimpleDependencyClass
{
public static readonly DependencyProperty SimpleDependencyProperty;
}

You normally append the Property suffix in the dependency property name to differentiate it from CLR property.

3.You need to register the dependency property.This is like creating an object of a CLR property.To register the dependency property you use the Register() method of DependencyProperty in the static constructor of the class:

SimpleDependencyProperty=DependencyProperty.Register(“SimpleDependency”, typeof(string), typeof(SimpleDependencyClass))

You supply the following values to the DependencyProperty Register method:

1. Name of the property
2. Data type of property
3. Data type of containing class.

Follow on:

This WPF tutorial for beginners will help you learn the main concepts of WPF.WPF is the current technology used for developing windows applications on the .NET framework.It supports the development of applications which utilizes the modern hardware such as GPU.

WPF stands for Windows Presentation Foundation.It is a framework for developing Windows applications.Prior to WPF ,windows forms was the technology used for developing Windows Applications.WPF provides several improvements over Windows Forms ,for developing windows applications.

The examples in this WPF tutorial are  implemented in C#.

Basics of WPF You will understand what is WPF

Styles in WPF Why to use Styles in WPF and how to implement styles.

Triggers in WPF What is the use of Triggers in WPF

Commands in WPF Why are Commands used in WPF

Data Templates What is the use of Data Template

DelegateCommand What is a Delegate Command

MVVM in WPF What is MVVM pattern

 

Follow on: