WPF: A TextBox that has an event that fires when the Enter Key is pressed
-
03-07-2019 - |
Question
Instead of attaching a PreviewKeyUp
event with each TextBox
in my app and checking if the pressed key was an Enter key and then do an action, I decided to implement extended version of a TextBox
that includes a DefaultAction event that fires when an Enter Key is pressed in a TextBox
.
What I did was basically create a new Class that extends from TextBox
with a public event DefaultAction
, like such:
public class DefaultTextBoxControl:TextBox
{
public event EventHandler<EventArgs> DefaultAction = delegate { };
public DefaultTextBoxControl()
{
PreviewKeyUp += DefaultTextBoxControl_PreviewKeyUp;
}
void DefaultTextBoxControl_PreviewKeyUp(object sender, System.Windows.Input.KeyEventArgs e)
{
if (e.Key != Key.Enter)
{
return;
}
DefaultAction(this, EventArgs.Empty);
}
}
I then use this custom textbox from my app like such (xaml):
<Controls:DefaultTextBoxControl DefaultAction="DefaultTextBoxControl_DefaultAction">
</Controls:DefaultTextBoxControl>
Now in my little experience I've had in learning WPF I've realized that almost most of the time there is a "cooler" (and hopefully easier) way to implement things
...so my question is, How can I improve the above control? Or maybe is there another way I can do the above control? ...maybe using only declarative code instead of both declarative (xaml) and procedural (C#) ?
Solution
Have a look at this blog post from a few months back where I attach a 'global' event handler to TextBox.GotFocus
to select the text.
Essentially you can handle the KeyUp
event in your App class, like this:
protected override void OnStartup(StartupEventArgs e)
{
EventManager.RegisterClassHandler(typeof(TextBox),
TextBox.KeyUpEvent,
new System.Windows.Input.KeyEventHandler(TextBox_KeyUp));
base.OnStartup(e);
}
private void TextBox_KeyUp(object sender, System.Windows.Input.KeyEventArgs e)
{
if (e.Key != System.Windows.Input.Key.Enter) return;
// your event handler here
e.Handled = true;
MessageBox.Show("Enter pressed");
}
... and now every TextBox
in your application will call the TextBox_KeyUp
method as users type into them.
Update
As you've pointed out in your comment, this is only useful if every TextBox
needs to execute the same code.
To add an arbitrary event like an Enter keypress, you might be better off looking into Attached Events. I believe this can get you what you want.
OTHER TIPS
Since this question was asked, there is now an InputBindings
property on TextBoxes and other controls. With this, a purely XAML solution can be used, rather than using custom controls. Assigning KeyBinding
s for Return
and Enter
to point to a command can do this.
Example:
<TextBox Text="Test">
<TextBox.InputBindings>
<KeyBinding Command="{Binding SomeCommand}" Key="Return" />
<KeyBinding Command="{Binding SomeCommand}" Key="Enter" />
</TextBox.InputBindings>
</TextBox>
Some have mentioned that Enter
does not always work, and Return
may be used on some systems.
When the user presses the Enter key in the TextBox, the input in the text box appears in another area of the user interface (UI).
The following XAML creates the user interface, which consists of a StackPanel, a TextBlock, and a TextBox.
<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>
The following code behind creates the KeyDown event handler. If the key that is pressed is the Enter key, a message is displayed in the TextBlock.
private void OnKeyDownHandler(object sender, KeyEventArgs e)
{
if (e.Key == Key.Return)
{
textBlock1.Text = "You Entered: " + textBox1.Text;
}
}
For more info read MSDN Doc
private void txtBarcode_KeyDown(object sender, KeyEventArgs e)
{
string etr = e.Key.ToString();
if (etr == "Return")
{
MessageBox.Show("You Press Enter");
}
}
add event in xaml
to the specific textbox or object:
KeyDown="txtBarcode_KeyDown"