如何在不按Enter键的情况下检测键盘C＃WPF

Question

How can i change this code to active detecion of my keyboard. Now it is showing what i write after press enter. How can i show what i can write without enter key.

XAML:

<StackPanel>
  <TextBlock Width="300" Height="20">
   Type some text into the TextBox and press the Enter key.
  </TextBlock>
  <TextBox Width="300" Height="30" Name="textBox1"
           KeyDown="OnKeyDownHandler"/>
  <TextBlock Width="300" Height="100" Name="textBlock1"/>
</StackPanel>

C#:

private void OnKeyDownHandler(object sender, KeyEventArgs e)
{
    if (e.Key == Key.Return)
    {
        textBlock1.Text = "You Entered: " + textBox1.Text;
    }
}

Or maybe is some diffrent way to create it?

Answer 1

You could simply bind the text directly:

<StackPanel>
  <TextBlock Width="300" Height="20">
   Type some text into the TextBox and it will appear in the field automatically.
  </TextBlock>
  <TextBox Width="300" Height="30" Name="textBox1" />
  <TextBlock Width="300" Height="100" Name="textBlock1" Text="{Binding Text, ElementName=textbox1}"/>
</StackPanel>

This way you don't need any code-behind.

EDIT

If you want more sophisticated stuff, try this. Implement a new class in your project like this:

public class MyConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return $"You entered: {value ?? "nothing"}";
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

and then change your binding to

<Window.Resources>
    <local:MyConverter x:Key="MyConverter"/>
</Window.Resources>
<StackPanel>
    <TextBox Name="txtEdit" />
    <TextBlock Text="{Binding Text, Converter={StaticResource MyConverter}, ElementName=txtEdit}" />
</StackPanel>

Don't forget the resources for the window.

Here is a screen video showing it in action:

Answer 2

textBlock1.Text = "You Entered: " + **textBox1.Text**;

Don't use direct control property, in contrast use MVVM and binding.

"The UpdateSourceTrigger property of a binding controls how and when a changed value is sent back to the source."

http://www.wpf-tutorial.com/data-binding/the-update-source-trigger-property/

Answer 3

If I correctly understood the question, you need tunneling PreviewKeyDown event:

private void OnPreviewKeyDown(object sender, KeyEventArgs e)
{
    if (e.Key == Key.G)
    {
        e.Handled = true;
    }
}

Alternatively, you can you use Keyboard class. In fact, Keyboard class can be used anywhere in your code:

private void SomeMethod()
{
    if (Keyboard.IsKeyDown(Key.LeftCtrl))
    {
        MessageBox.Show("Release left Ctrl button");
        return;
    }
    //Do other work
}