textbox回车事件中拿不到text的处理办法(wpf)

"SearchBox" Grid.Column="1"  Margin="350,35,52,21" 122" 34" RenderTransformOrigin="0.5,0.5" Text="{Binding Keyword}" PreviewKeyDown="SearchBox_OnKeyDown">
            
                "Enter" Command="{Binding SearchCommand}" />
            
        
        "btnSearch" Grid.Column="2" HorizOntalAlignment="Left" 34" Margin="29.5,38,0,0" VerticalAlignment="Top" 34" Command="{Binding SearchCommand}" >
            34" 34" Source="/Icons/SearchIcon.png"/>
        

private void SearchBox_OnKeyDown(object sender, KeyEventArgs e)
        {
            if (e.Key == Key.Enter)
            {
                SearchBox.MoveFocus(new TraversalRequest(FocusNavigationDirection.Next));
            }
        }