Example: Changing Selected Records in Provider and Unbound Modes

• Jul 29, 2021
• 3 minutes to read

The following example shows how to access selected records in provider and unbound modes.

The total number of selected rows (data records and grouping rows) is determined by the DataController.GetSelectedCount function. To iterate selected rows in unbound and provider modes, the data controller’s GetSelectedRowIndex method must be used. It returns the row index of a specific selected row that can be used to retrieve information on the row using the GetRowInfo function.

Suppose that records of the data controller are displayed within a tvOrders view of the ExpressQuantumGrid control. The following code shows how to change the tvOrdersSaleDate column values of selected records to the current date.

Delphi

var
  I: Integer;
  ARowIndex: Integer;
  ARowInfo: TcxRowInfo;
begin
  with tvOrders.DataController do
  begin
    BeginUpdate;
    try
      for I := 0 to GetSelectedCount - 1 do
      begin
        ARowIndex := GetSelectedRowIndex(I);
        ARowInfo := GetRowInfo(ARowIndex);
        //Test whether a row is a grouping row
        if ARowInfo.Level < Groups.GroupingItemCount then
          Continue
        else
          //unbound or provider mode
          Values[ARowInfo.RecordIndex, tvOrdersSaleDate.Index] := Now();
      end;
    finally
      EndUpdate;
    end;
  end;
end;

C++

TcxCustomDataController * dc = tvOrders->DataController;
  int ARowIndex;
  TcxRowInfo ARowInfo;
  dc->BeginUpdate();
  try {
    for (int I = 0; I < dc->GetSelectedCount(); I++) {
      ARowIndex = dc->GetSelectedRowIndex(I);
      ARowInfo = dc->GetRowInfo(ARowIndex);
      //Test whether a row is a grouping row
      if (ARowInfo.Level < 
          dc->Groups->GroupingItemCount)
        continue;
      else
        dc->Values[ARowInfo.RecordIndex] 
          [tvOrdersSaleDate->Index] = Now();
    }
  }
  __finally {
    dc->EndUpdate();
  }

The following code demonstrates another approach to access selected records. The data controller provides the ForEachRow method to call a custom procedure (a callback function) automatically for each row. This method is overridden by the TcxDBDataController class, so you can use it in all loading modes (provider, unbound, bound, and grid mode).

The first parameter defines whether selected or all rows should be processed. The custom procedure to be called for each row, is passed as the second parameter of ForEachRow.

To use the ForEachRow method, you have to write a procedure with a specific prototype (see the method’s description). This procedure should perform operations on a row. In our example, it changes the tvOrdersSaleDate column value:

Delphi

procedure TForm1.SetSaleDate(ARowIndex: Integer; ARowInfo: TcxRowInfo);
begin
  with tvOrders.DataController do
  begin
    //Test whether a row is a data record
    if ARowInfo.Level = Groups.GroupingItemCount then
      //unbound or provider mode
      Values[ARowInfo.RecordIndex, tvOrdersSaleDate.Index] := Now();
  end;
end;

C++

void __fastcall TForm1::SetSaleDate(int ARowIndex, const TcxRowInfo &ARowInfo) {
  TcxCustomDataController * dc = tvOrders->DataController;
  //Test whether a row is a data record
  if (ARowInfo.Level == dc->Groups->GroupingItemCount)
    //unbound or provider mode
    dc->Values[ARowInfo.RecordIndex][tvOrdersSaleDate->Index] = Now();
}

The code that calls the SetSaleDate method for each row is shown below:

Delphi

with tvOrders.DataController do
  begin
    BeginUpdate;
    try
      ForEachRow(True, SetSaleDate);
    finally
      EndUpdate;
    end;
  end;

C++

TcxCustomDataController * ADataController = 
    tvOrders->DataController;
  ADataController->BeginUpdate();
  try {
    ADataController->ForEachRow(True, SetSaleDate);
  }
  __finally {
    ADataController->EndUpdate();
  }