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PivotGridControl can perform data-aware operations (retrieving data from the server, sorting, grouping, filtering data and calculating summaries) in a background thread, allowing the entire application to stay responsive while these operations are in progress.
If PivotGridControl is working with a large dataset, retrieving data from a data source, as well as performing various data-aware operations, such as sorting or filtering data, may take a considerable amount of time. In a standard (synchronous) mode, the entire application would not respond to user actions until PivotGridControl completes the required operations, since the primary UI thread is busy. End-users can notice a small or considerable application freeze.
In an asynchronous mode, only PivotGridControl is frozen. The application continues interacting with an end-user, while the control is processing data in a background thread. While processing data, PivotGridControl displays a loading panel to indicate that this control is busy and would not respond to user actions until the operation is completed.
You can specify whether data-aware operations caused by end-user actions run synchronously or asynchronously. To do this, use the PivotGridControl.UseAsyncMode property. If this property is set to true, all operations performed via the UI are asynchronous.
Operations Run In Code
In code, you can perform both synchronous and asynchronous operations, regardless of the UI settings. All methods whose names end with ...Async are asynchronous, i.e., they start executing the related operation in a background thread and return control.
You can perform a data-aware operation asynchronously even if there is no special ...Async method implemented. The PivotGridControl provides the PivotGridControl.EndUpdateAsync method that allows you to apply the changes made to the control in a background thread. For instance, you can customize the PivotGridControl via its properties, wrap the code in the PivotGridControl.BeginUpdate and PivotGridControl.EndUpdateAsync method calls, and the control will be updated asynchronously.
To ensure that the PivotGridControl.EndUpdateAsync method is executed even if an exception occurs, wrap calls to the PivotGridControl.BeginUpdate and PivotGridControl.EndUpdateAsync methods in a try..finally statement.
Note that you cannot start a data-aware operation in code while another operation is running in a background thread.
Subsequent Actions and Operation Result
Each asynchronous method has an overload that allows you to specify custom actions to be performed after the asynchronous operation is completed. To do this, pass an AsyncCompletedHandler delegate that performs the required actions as the asyncCompleted parameter.
If an asynchronous method returns data (an operation result), you must pass a delegate to obtain this data. The delegate's result parameter returns an AsyncOperationResult instance. Use the AsyncOperationResult.Value property to obtain the operation result, and the AsyncOperationResult.Exception property to determine whether an exception has been thrown during the operation execution.
Execution of Asynchronous Operations
The PivotGridControl performs the following actions after an asynchronous operation has been triggered:
- closes all popup menus and windows, disables the UI and loses focus (if it was focused);
- raises the PivotGridControl.AsyncOperationStarting event;
- locks access to pivot grid data through API, shows a loading panel and runs background calculations.
After background calculations are finished, the PivotGridControl does the following:
- unlocks access to pivot grid data through API, hides the loading panel and activates the UI;
- raises the PivotGridControl.AsyncOperationCompleted event;
- performs internal handling of the operation results;
- executes a custom delegate (if one has been passed).
Event Handling Specifics
In an asynchronous mode, events that allow you to control summary calculation are handled in a background thread. This regards the following events:
- PivotGridControl.FieldValueDisplayText (handled in a background thread if a field's PivotGridField.SortMode property is set to FieldSortMode.DisplayText)
For thread safety, you cannot use event parameter properties that return PivotGridField objects in an asynchronous mode, since it is not safe to access pivot grid fields from a background thread. Each of these properties has a thread-safe counterpart whose name starts with the prefix ThreadSafe. These properties return objects that implement the IThreadSafeField interface, which provides thread-safe read-only access to pivot grid fields, allowing you to obtain the required information.
This section lists methods exposed by PivotGridControl that perform various operations asynchronously.
|PivotGridControl.ReloadDataAsync||Reloads data from the control data source and recalculates summaries asynchronously.|
|PivotGridControl.RetrieveFieldsAsync||Creates PivotGridField objects for all fields in a data source asynchronously.|
|PivotGridControl.SetDataSourceAsync||Sets a data source for PivotGridControl and loads data asynchronously.|
|PivotGridControl.SetOlapConnectionStringAsync||Sets a connection string to a cube in an MS Analysis Services database, and loads data from the cube asynchronously.|
|PivotGridControl.ChangeFieldSortOrderAsync||Toggles the sort order of the specified field asynchronously.|
|PivotGridControl.SetFieldSortingAsync||Sets the specified sort order for the specified field asynchronously.|
|PivotGridControl.ChangeFieldExpandedAsync||Expands or collapses all values of the specified field asynchronously.|
|PivotGridControl.CollapseAllAsync||Collapses all columns and rows in PivotGridControl asynchronously.|
|PivotGridControl.CollapseAllColumnsAsync||Collapses all columns asynchronously.|
|PivotGridControl.CollapseAllRowsAsync||Collapses all rows asynchronously.|
|PivotGridControl.CollapseValueAsync||Collapses the specified column or row asynchronously.|
|PivotGridControl.ExpandAllAsync||Expands all columns and rows in the PivotGridControl asynchronously.|
|PivotGridControl.ExpandAllColumnsAsync||Expands all columns asynchronously.|
|PivotGridControl.ExpandAllRowsAsync||Expands all rows asynchronously.|
|PivotGridControl.ExpandValueAsync||Expands the specified column or row asynchronously.|
|PivotGridControl.RestoreCollapsedStateFromStreamAsync||Restores the collapsed state of field values from the specified stream asynchronously.|
|PivotGridControl.RestoreLayoutFromStreamAsync||Restores the pivot grid layout from the specified stream asynchronously. Allows you to specify custom actions to be performed after this operation is completed.|
|PivotGridControl.RestoreLayoutFromXmlAsync||Restores the pivot grid's layout from the specified XML file asynchronously. Allows you to specify custom actions to be performed after this operation is completed.|
|PivotGridControl.CreateDrillDownDataSourceAsync||Returns a list of records used to calculate summary values for all cells asynchronously.|
|PivotGridControl.CreateOlapDrillDownDataSourceAsync||Obsolete. In OLAP mode, returns a list of records used to calculate a summary value for the specified cell asynchronously. Allows you to specify which columns should be returned.|
|PivotGridControl.EndUpdateAsync||Unlocks the PivotGridControl after the PivotGridControl.BeginUpdate method call, and starts an asynchronous update.|