TDBGrid Duplicating rows

Question

I am converting some software from Delphi 5 to Delphi 10.2.

We have a TDBGrid that is linked to a datasource that is link to a table. So something like this:

TDBGrid.DataSource := GroupDS;
GroupDS.DataSet := MemoryTable;

The MemoryTable has 1 record in it. However, no matter what I've tried the TDBGrid is duplicating the single record. This behavior only happens in D10.2. In D5 it shows the single record normally. I can call RecordCount on the table and verify that there is only 1 record present in it.

Please let me know if there is any other info I can provide. This is all taking place in VCL stuff so there isn't much code to show. I don't know if maybe something changed in the 20 years between the releases of the IDEs.

I wrote a test app to recreate this issue.

Code:

EmpGrpMember := InitializeACRTable;

EmpGrpMember.InMemory := True;
EmpGrpMember.IndexDefs.Add('GroupGUID', 'GroupGUID', [ixPrimary, ixUnique]);
EmpGrpMember.IndexDefs.Add('GroupName', 'GroupName', [ixUnique]);
EmpGrpMember.IndexName := 'GroupName';
EmpGrpMember.FieldDefs.Add('GroupGUID', ftString, 40);
EmpGrpMember.FieldDefs.Add('GroupName', ftString, 100);
EmpGrpMember.TableName := 'EmpGrpMember';

EmpGrpMemberDS.DataSet := EmpGrpMember;
DBGrid1.DataSource := EmpGrpMemberDS;
EmpGrpMember.Open;
EmpGrpMember.Insert;
EmpGrpMember.FieldByName('GroupGUID').AsString := '123';
EmpGrpMember.FieldByName('GroupName').AsString := 'wwww';
EmpGrpMember.Post;

dfm:

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 336
  ClientWidth = 635
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  PixelsPerInch = 96
  TextHeight = 13
  object DBGrid1: TDBGrid
    Left = 144
    Top = 96
    Width = 225
    Height = 121
    Options = [dgTitles, dgColumnResize, dgColLines, dgRowLines, dgTabs, dgRowSelect, dgAlwaysShowSelection, dgConfirmDelete, dgCancelOnExit]
    TabOrder = 0
    TitleFont.Charset = DEFAULT_CHARSET
    TitleFont.Color = clWindowText
    TitleFont.Height = -11
    TitleFont.Name = 'Tahoma'
    TitleFont.Style = []
    Columns = <
      item
        Expanded = False
        FieldName = 'GroupName'
        Title.Caption = 'Member of Groups'
        Width = 191
        Visible = True
      end>
  end
  object EmpGrpMemberDS: TDataSource
    Left = 488
    Top = 216
  end
end

I still get the same results. My dbgrid ends up showing 4 'www' and it should only be showing 1. I do a .recordcount on the table and it only shows 1 record.

Answer 1

The minimal sample project below virtually exactly replicates your project except that it uses a TClientDataSet as the dataset instead of the AddAim one.

It correctly shows only a single row. Ergo the problem lies with the use of a TACRTable. So, unless you get lucky and someone here recognises the problem and knows how to fix it, you'll need to take the problem up with AddAim.

Code:

  type
    TForm1 = class(TForm)
      DataSource1: TDataSource;
      DBGrid1: TDBGrid;
      EmpGrpMember: TClientDataSet;
      procedure FormCreate(Sender: TObject);
    public
    end;

  [...]
  procedure TForm1.FormCreate(Sender: TObject);
  var
    AField : TField;
  begin
    AField := TStringField.Create(Self);
    AField.FieldKind := fkData;
    AField.FieldName := 'GroupGUID';
    AField.Size := 255;
    AField.DataSet := EmpGrpMember;

    AField := TStringField.Create(Self);
    AField.FieldKind := fkData;
    AField.Size := 255;
    AField.FieldName := 'GroupName';
    AField.DataSet := EmpGrpMember;

    EmpGrpMember.IndexDefs.Add('GroupGUID', 'GroupGUID', [ixPrimary, ixUnique]);
    EmpGrpMember.IndexDefs.Add('GroupName', 'GroupName', [ixUnique]);
    EmpGrpMember.IndexName := 'GroupName';

    EmpGrpMember.CreateDataSet;
    EmpGrpMember.InsertRecord(['123', 'www']);

  end;

Of course, if you can replicate your problem by modifying the above project, there may be something worth looking into.

Update To debug your problem, set up a handler for the DrawCell event of the grid, like this

procedure TForm1.DBGrid1DrawColumnCell(Sender: TObject; const Rect: TRect;
  DataCol: Integer; Column: TColumn; State: TGridDrawState);
begin
  DataCol := DataCol;
end;

Put a breakpoint in it. When the breakpoint trips, you should find that tracing into the VCL source from it, you eventually arrive at a while loop inside the DrawCells procedure in Grids.Pas. Inspecting the while 's condition should show you why you are getting the row displayed twice.