Delphi : Avoid editing a column in TDBgrid - delphi

Question

I know that using a column's readonly property, i can avoid editing its field value. But this doesn't stop the inplace editor to show itself.
I need a way to make the column not only protected but "untouchable".
Is there a way, please ?

Answer 1

If I understand what you want correctly, you can do this quite simply, by creating a custom TDBGrid descendant and overriding
its CanEditShow method, as this determines whether the grid's InplaceEditor can be created:
type
TMyDBGrid = class(TDBGrid)
private
FROColumn: Integer;
protected
function CanEditShow : Boolean; override;
public
property ROColumn : Integer read FROColumn write FROColumn;
end;
function TMyDBGrid.CanEditShow: Boolean;
begin
Result := Inherited CanEditShow;
Result := Result and (Col <> ROColumn);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
MyDBGrid := TMyDBGrid.Create(Self);
MyDBGrid.ROColumn := 1;
MyDBGrid.DataSource := DataSource1;
MyDBGrid.Parent := Self;
[...]
This minimalist example just defines one grid column by number as being one
where the InplaceEditor is not permitted; obviously you could use any mechanism
you like to identify the column(s) for which CanEditShow returns False.
Note that the code above doesn't account for the fact that the column numbering of the grid changes if you turn off the Indicator column (i.e. set Options.dgIndicator to False);
Obviously, you get more flexibility for customizing which columns are permitted an InplaceEditor by using an assignable event as in
type
TAllowGridEditEvent = procedure(Sender : TObject; var AllowEdit : Boolean) of object;
TMyDBGrid = class(TDBGrid)
private
FOnAllowEdit: TAllowGridEditEvent;
protected
function CanEditShow : Boolean; override;
procedure DoAllowEdit(var AllowEdit : Boolean);
public
property OnAllowEdit : TAllowGridEditEvent read FOnAllowEdit write FOnAllowEdit;
end;
function TMyDBGrid.CanEditShow: Boolean;
begin
Result := Inherited CanEditShow;
if Result then
DoAllowEdit(Result);
end;
procedure TMyDBGrid.DoAllowEdit(var AllowEdit: Boolean);
begin
if Assigned(FOnAllowEdit) then
FOnAllowEdit(Self, AllowEdit);
end;
procedure TForm1.AllowEdit(Sender: TObject; var AllowEdit: Boolean);
var
Grid : TMyDBGrid;
begin
Grid := Sender as TMyDBGrid;
AllowEdit := Grid.Col <> 1;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
MyDBGrid := TMyDBGrid.Create(Self);
MyDBGrid.ROColumn := 1;
MyDBGrid.DataSource := DataSource1;
MyDBGrid.Parent := Self;
MyDBGrid.OnAllowEdit := AllowEdit;
[...]
If you don't like creating the grid in code, you could put it in a custom package and install it
in the IDE or, if your Delphi version is recent enough, implement the
CanEditShow in a class helper.