Windows Presentation Foundation (WPF) is a UI framework provided by Microsoft, and it is a powerful tool for developing desktop applications. By using WPF, you can maximize user experience utilizing features such as data binding, templates, styling, and animations. This course will explain in detail how to display messages from data objects using WPF.
1. Overview
WPF adopts the MVVM (Model-View-ViewModel) design pattern, helping to enhance maintainability and increase testability by providing separation between UI and data. In the process of displaying messages from data objects, we learn how to convey the information contained in data objects to the user.
2. WPF and Data Binding
The data binding feature of WPF sets up a connection between data objects and UI elements. This allows changes in data to be automatically reflected in the UI, and user inputs from the UI to be immediately reflected in the data objects. In this section, we will create a simple data object and bind it to WPF’s UI to display messages.
2.1 Defining Data Objects
First, we define the data object that will convey messages. This object contains properties for the message and methods to display that message.
using System.ComponentModel;
public class Message : INotifyPropertyChanged
{
private string _content;
public string Content
{
get { return _content; }
set
{
_content = value;
OnPropertyChanged(nameof(Content));
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
The code above defines a data structure containing the message content (Content) and implements the INotifyPropertyChanged interface to notify the UI when properties change.
2.2 Designing the WPF UI
Now we can design the WPF UI to display messages. Add the following content to the XAML file.
<Window x:Class="WpfApp.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Message Display Example" Height="200" Width="400">
<Grid>
<TextBox x:Name="MessageTextBox"
Width="300" Height="30"
Margin="10"
Text="{Binding Content, UpdateSourceTrigger=PropertyChanged}" />
<Button Content="Send Message"
Width="100" Height="30"
Margin="10,50,0,0"
Click="OnSendMessage"/>
</Grid>
</Window>
The XAML code above defines a simple UI that includes a text box and a button. The text in the text box is bound to the Content property of the data object, so the message entered by the user is automatically reflected.
2.3 Writing the Code-Behind File
To connect the UI and the data object, add the logic for handling messages in MainWindow.xaml.cs.
using System.Windows;
public partial class MainWindow : Window
{
private Message _message;
public MainWindow()
{
InitializeComponent();
_message = new Message();
DataContext = _message;
}
private void OnSendMessage(object sender, RoutedEventArgs e)
{
MessageBox.Show("Sent message: " + _message.Content);
}
}
In the above code, the constructor for MainWindow initializes the data object and sets the data context to connect with the UI elements defined in the XAML file. A message box is also added to show the message entered upon button click.
3. Improving User Experience
You can add various features to enhance user experience. For example, let’s implement functionality to add messages and display a list of messages.
3.1 Message List and Addition Functionality
Now, we will add functionality for users to input multiple messages and display them in a list. We will create a new class to manage the list of messages.
using System.Collections.ObjectModel;
public class MessageCollection : INotifyPropertyChanged
{
private ObservableCollection<Message> _messages;
public ObservableCollection<Message> Messages
{
get { return _messages; }
set
{
_messages = value;
OnPropertyChanged(nameof(Messages));
}
}
public MessageCollection()
{
Messages = new ObservableCollection<Message>();
}
public void AddMessage(string content)
{
Messages.Add(new Message { Content = content });
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
The MessageCollection class uses ObservableCollection to store messages, allowing the UI to automatically detect changes in the data.
3.2 UI Update
We will modify the UI to add a ListBox to display the list of messages and allow new messages to be added.
<Grid>
<TextBox x:Name="MessageTextBox"
Width="300" Height="30"
Margin="10"
Text="{Binding NewMessage.Content, UpdateSourceTrigger=PropertyChanged}" />
<Button Content="Send Message"
Width="100" Height="30"
Margin="10,50,0,0"
Click="OnSendMessage"/>
<ListBox ItemsSource="{Binding Messages}"
Margin="10,100,10,10">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Content}" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
The UI has now been updated to view multiple messages in a list and to add content instantly.
3.3 Updating the Code-Behind
Now, we will update the MainWindow.xaml.cs file to utilize the MessageCollection.
using System.Windows;
public partial class MainWindow : Window
{
private MessageCollection _messageCollection;
public MainWindow()
{
InitializeComponent();
_messageCollection = new MessageCollection();
DataContext = _messageCollection;
}
private void OnSendMessage(object sender, RoutedEventArgs e)
{
_messageCollection.AddMessage(_messageCollection.NewMessage.Content);
MessageBox.Show("Sent message: " + _messageCollection.NewMessage.Content);
_messageCollection.NewMessage.Content = string.Empty; // Clear the textbox after sending
}
}
In the above code, we added the functionality to add the message input by the user to the MessageCollection, and to clear the text box after the message has been sent.
4. Moving Forward
We have now completed the basic message display functionality. From here, you can add various features, such as:
- Message deletion functionality
- Message editing functionality
- Displaying the time for messages
- Implementing styles and animations in the UI
By adding these functions, you can enrich the user experience even further.
5. Conclusion
In this lecture, we learned how to display messages from data objects using WPF. We have acquired basic knowledge about data binding, the MVVM pattern, and improving user experience. By utilizing these techniques, you can develop more complex and useful applications. WPF is an excellent framework that can provide various possible scenarios and unique user experiences.
We look forward to exploring more commands and convenient libraries in WPF in the future.