在TextBox上输入KeyDown，将空值保存到数据库中

Question

Having strange behaviour. I am creating some sort of chat, in scope of which I have a TextBox, (which holds new message) and a method which sends this text to a database as a new message. I am calling for the sendMessage method in two separated ways:
1. By clicking (Click) on a button;
2. By pressing enter (KeyDown) on the TextBox.

Now the strange behaviour: Click event saves the Text, all is ok.
Enter key - sends one of two:
Or null (if in the current Controler session Enter key is the first, who invokes sendMessage);
Or the last saved message, which was invoked by Click.

Here are the code snipets:

XAML

<Border Name="tbWriteMessage"
        Grid.Column="0"
        Grid.Row="2"
        Background="White"
        Width="{Binding Path=ActualWidth, ElementName=Ruler}"
        BorderBrush="{StaticResource BlueBrush}"
        BorderThickness="0,2,0,0">
    <TextBox Style="{StaticResource EnterMessageWatermark}"
             Text="{Binding Message}"
             KeyDown="tbNewMessage_KeyDown"
             x:Name="tbNewMessage"
             MaxHeight="21"/>
</Border>
<Button Style="{StaticResource Button}" 
        Name="btnEnviar"
        Click="btnEnviar_Click"
        Grid.Column="1"
        Grid.Row="2"
        VerticalAlignment="Top"
        Width="100"
        Height="23"
        Content="Enviar"
        BorderThickness="2,2,0,0"/>

CS

private void sendMessage()
{
    _viewModel.SaveNewMessage();
    tbNewMessage.Clear();
}

private void btnEnviar_Click(object sender, RoutedEventArgs e)
{
    sendMessage();
}

private void tbNewMessage_KeyDown(object sender, KeyEventArgs e)
{
    if (e.Key == Key.Enter)
    {   
        sendMessage();
    }   
}

Would be more than grateful for pointing me the best approach in solving this obstacle.
Thank you in advance!

Answer 1

Ok, I found a workaround which is not so bad.
On key Enter I do:
1. Send focus on different object (in my case it was the button, but it does not really matter).
2. invoke sendMessage.
3. set focus back on TextBox.