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unit Unit56;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Data.DB, MemDS, VirtualDataSet,
  Vcl.Grids, Vcl.DBGrids, DBAccess, Uni, System.Generics.Collections;

type
  TGUIDClass = class
    GUID1: TGUID;
    GUID2: TGUID;
  end;

  TForm56 = class(TForm)
    VirtualDataSet1: TVirtualDataSet;
    gfGUID1: TGuidField;
    gfGUID2: TGuidField;
    UniDataSource1: TUniDataSource;
    DBGrid1: TDBGrid;
    procedure FormDestroy(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure VirtualDataSet1GetFieldValue(Sender: TObject; Field: TField; RecNo:
        Integer; out Value: Variant);
    procedure VirtualDataSet1GetRecordCount(Sender: TObject; out Count: Integer);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
    FGUIDList : TObjectList<TGUIDClass>;
  end;

var
  Form56: TForm56;

implementation

{$R *.dfm}

procedure TForm56.FormDestroy(Sender: TObject);
begin
 FreeAndNil( FGUIDList);
end;

procedure TForm56.FormCreate(Sender: TObject);
begin
 FGUIDList := TObjectList<TGUIDClass>.Create( True);
 for var i := 0 to 10 do
 begin
  var lGUIDObject := TGUIDClass.Create;
  lGUIDObject.GUID1 := TGUID.NewGuid;
  lGUIDObject.GUID2 := TGUID.NewGuid;
  FGUIDList.Add( lGUIDObject);
 end;
 VirtualDataSet1.Open;
end;

procedure TForm56.VirtualDataSet1GetFieldValue(Sender: TObject; Field: TField;
    RecNo: Integer; out Value: Variant);
begin
// If I leave only one of the fields in it is displayed correctly, no matter which field
 case Field.Index of
  0: Value := FGUIDList[ RecNo-1].GUID1.ToString;
  1: Value := FGUIDList[ RecNo-1].GUID2.ToString;
 end;
end;

procedure TForm56.VirtualDataSet1GetRecordCount(Sender: TObject; out Count:
    Integer);
begin
 Count := FGUIDList.Count;
end;

end.

Code: Select all

procedure TForm56.DBGrid1CellClick(Column: TColumn);
begin
 ShowMessage( 'Field-GUID1 | Value: ' + gfGUID1.Value + sLineBreak + //wrong
              'Field-GUID1 | AsGuid.ToString: ' + gfGUID1.AsGuid.ToString + sLineBreak + //correct
              'Field-GUID1 | AsString: ' + gfGUID1.AsString + sLineBreak +//wrong
              'FGUIDList-GUID1 | ToString: ' + FGUIDList[ VirtualDataSet1.RecNo-1].GUID1.ToString); //correct
end;