Keydown Event fires twice

Question

On a Windows store App, I have this simple TextBox ``` <TextBox Name="TextBoxUser" HorizontalAlignment="Right" Width="147" Margin="20,0,0,0" KeyDown="TextBox_KeyDown" / ``` That has a KeyDown Event associated with it. ``` private async void TextBox_KeyDown(object sender, KeyRoutedEventArgs e) { if (e.Key == Windows.System.VirtualKey.Enter) { Debug.WriteLine("LA"); } } ``` And the output of this function is: LA LA although I press Enter only once, it prints 2 times. Any reason for that or am I doing something wrong?

Accepted Answer

This should only fire the event once, so if it is firing twice I would check a couple of things.

Check that you aren't handling the key down event on a parent control. This could be a panel or the containing window. Events will bubble down through the visual tree. For example a key down on a textbox will also be a keydown on the window containing the textbox.

To stop this happening you can mark the event as handled as below;

```
e.Handled = true;
```

The other thing to check is that you aren't subscribing to the event twice. The XAML will do the same as;

TextBoxUser.KeyDown += TextBox_KeyDown

so check that you don't have this in your code behind.

You can check the sender and e.OriginalSource property to see where the event is being fired from.

Keydown Event fires twice

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