TcxFilterCriteria.BeginUpdate Method

Postpones all filter criteria calculations and corresponding UI redraw operations until an EndUpdate procedure call.

Declaration

procedure BeginUpdate;

Remarks

Every time you change filter criteria, the data controller notifies the control about the corresponding data change. Enclose multiple filter criteria changes between BeginUpdate and EndUpdate procedure calls to avoid UI flickering due to excessive redraw operations and improve performance.

BeginUpdate/EndUpdate Calls and Batch Changes

A BeginUpdate procedure call disables notifications and postpones all filter criteria changes until an EndUpdate call. A subsequent EndUpdate call does the following:

• Re-enables change notifications and corresponding redraw operations
• Applies all changes made after a BeginUpdate call
• Sends corresponding notifications in a batch
• Redraws the parent control

Note

Ensure that every BeginUpdate procedure call is followed by an EndUpdate or CancelUpdate call, even if an exception occurs.

Code Example

The code example in this section applies the following filter criteria to CustomerCount and Name data grid columns:

  (CustomerCount < 1000) AND ((Name LIKE 'A%') OR (Name LIKE 'Z%'))

Delphi

var
  ADataController: TcxGridDBDataController;
  AItemList: TcxFilterCriteriaItemList;
begin
  ADataController := cxDBTableView1.DataController;
  ADataController.Filter.BeginUpdate;  // Initiates the following batch data controller change
  try
    ADataController.Filter.Root.Clear;
    ADataController.Filter.Root.AddItem(cxDBTableView1CustomerCount, foLess, 1000, '1000');
    AItemList := ADataController.Filter.Root.AddItemList(fboOr);
    AItemList.AddItem(cxDBTableView1Name, foLike, 'A%', 'A%');
    AItemList.AddItem(cxDBTableView1Name, foLike, 'Z%', 'Z%');
    ADataController.Filter.Active = True;
  finally
    ADataController.Filter.EndUpdate;  // Calls EndUpdate regardless of the batch operation's success
  end;
end;

C++

  TcxGridDBDataController *ADataController = cxDBTableView1->DataController;
  TcxFilerCriteriaItemList *AItemList;
  ADataController->Filter->BeginUpdate();  // Initiates the following data controller change
  try {
    ADataController->Filter->Root->Clear();
    ADataController->Filter->Root->AddItem(cxDBTableView1CustomerCount, foLess, 1000, "1000");
    AItemList = ADataController->Filter->Root->AddItemList(fboOr);
    AItemList->AddItem(cxDBTableView1Name, foLike, "A%", "A%");
    AItemList->AddItem(cxDBTableView1Name, foLike, "Z%", "Z%");
    ADataController->Filter->Active = true;
} __finally {
    ADataController->Filter->EndUpdate();  // Calls EndUpdate regardless of the batch operation's success
}