Modified different way. fixed a bug not triggered while the backspace was pressed.

Author: Sparrkle

Flow.Launcher/MainWindow.xaml

@@ -173,7 +173,7 @@
                         Background="Transparent"
                         PreviewDragOver="OnPreviewDragOver"
                         Style="{DynamicResource QueryBoxStyle}"
-                        Text="{Binding QueryText, Mode=TwoWay, UpdateSourceTrigger=Explicit}"
+                        Text="{Binding QueryText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                         PreviewKeyUp="QueryTextBox_KeyUp"
                         Visibility="Visible">
                         <TextBox.CommandBindings>

Flow.Launcher/MainWindow.xaml.cs

@@ -560,7 +560,8 @@ public void InitializeColorScheme()
 
         private void QueryTextBox_KeyUp(object sender, KeyEventArgs e)
         {
-            _viewModel.ChangeQueryText(QueryTextBox.Text);
+            if(_viewModel.QueryText != QueryTextBox.Text)
+                _viewModel.QueryText = QueryTextBox.Text;
         }
     }
 }