Instant Feedback UI Mode

• Apr 24, 2019
• 3 minutes to read

The Instant Feedback Mode is very similar in concept with the Server Mode in that data is retrieved only in portions that are required to populate the view and data-aware operations are performed on the server. Instant Feedback Mode is however an asynchronous server mode. The difference lies in how the grid behaves when data is being retrieved and populated.

When a user scrolls through the records in a Server Mode, the grid first waits for the partial data to be fetched before populating the rows. Depending on the data source performance, the volume of data being retrieved, and the network connectivity, the user may notice a considerable control freeze. Instant Feedback Mode addresses this issue by continuing to respond to the user’s actions while the data is being retrieved. The user can continue to scroll through records, and even re-sort, re-group and re-filter the control’s data. If required, the control will cancel the previous request and initiate a new request to the data source.

To activate this feature, use our specially designed data sources - LinqInstantFeedbackDataSource, XPInstantFeedbackSource, EntityInstantFeedbackDataSource or WcfInstantFeedbackDataSource. To see the Instant Feedback mode in action, take a look at the Entity Framework module in the WPF Data Grid Demo.

To avoid thread-safety issues, all Instant Feedback data providers retrieve wrappers for objects, but not actual objects, if their AreSourceThreadSafe property is not set to false. When binding in XAML, use the Data object as shown in the code snippet below.

XAML

<Setter Property="ToolTip" Value="{Binding Path=Data.Parameter.Description}" />

You can also use a special converter - dxg:RowPropertyValueConverter, to get a value from the wrapper. See examples below.

• RowStyle:

  XAML

  <dxg:RowPropertyValueConverter x:Key="rowPropertyConverter" />
  ...
  <DataTrigger Binding="{Binding Path=DataContext, Converter={StaticResource rowPropertyConverter}, ConverterParameter=IsSeen}" Value="True">
      <Setter Property="FontWeight" Value="Bold" />
  </DataTrigger>
  

• CellStyle/CellTemplate

  XAML

  <dxg:RowPropertyValueConverter x:Key="rowPropertyConverter" /> 
  ...
  <TextBlock Text="{Binding Converter={StaticResource rowPropertyConverter}, ConverterParameter=yourPropertyName}" />
  

To provide visual feedback, the Instant Feedback binding mode also includes options to display an animation indicating the status of operations within the grid.

Property	Description
DataViewBase.RowAnimationKind	Specifies which animation is played while data is being asynchronously retrieved by the data source.
DataViewBase.WaitIndicatorType	Specifies how asynchronous data loading operations are indicated.
DataViewBase.WaitIndicatorStyle	Specifies the template that defines the wait indicator’s presentation.

The grid control provides two events that fire after asynchronous data loading has been started and completed. These events are: GridControl.AsyncOperationStarted and GridControl.AsyncOperationCompleted. The GridControl.IsAsyncOperationInProgress property indicates the current status of asynchronous data loading.

Note

• Instant feedback UI mode cannot be used in master-detail mode.
• Filter Elements, new FilterEditorControl, drop-down filter in ExcelSmart mode, Predefined Filters are not supported.

Examples

• How to: Implement the Instant Feedback Mode (XPO)
• How to: Activate the Instant Feedback Mode for the Grid Bound to the Entity Framework 4.0 Classes