TADODataset catch Post method error code in Delphi - delphi

Question

I have a dataset, and I'm using this to catch the errors:
try
FDataSource.DataSet.Post;
ShowMessage('success message!');
except
on E : EDatabaseError do
begin
if (Pos('duplicate value', E.Message) > 0) or (Pos('duplicate key', E.Message) > 0) then
ShowMessage('my custom error message')
else
ShowMessage('generic db error message');
end;
end;
This is a horrible solution cause it's relying on finding the string 'duplicate value' or 'duplicate key' on the error message.
I want to be able to get some error code.
Is there any way to get it?

Answer 1

You may be able to catch the error via your AdoConnection object.
The TAdoConnection has an Errors object (see definition in AdoInt.Pas). To
investigate it, I used a stored proc on the server defined as
create PROCEDURE [dbo].[spRaiseError](#AnError int)
AS
BEGIN
declare #Msg Char(20)
if #AnError > 0
begin
Select #Msg = 'MyError ' + convert(Char(8), #AnError)
RaisError(#Msg, 16, -1)
end
else
select 1
END
Then, in my Delphi code I have something like this:
uses [...] AdoInt, AdoDB, [...]
procedure TForm1.Button1Click(Sender: TObject);
var
S : String;
IErrors : Errors;
IError : Error;
ErrorCount : Integer;
i : Integer;
begin
S := 'exec spRaiseError ' + Edit1.Text;
AdoQuery1.SQL.Text := S;
try
AdoQuery1.Open;
except
IErrors := AdoConnection1.Errors;
ErrorCount := IErrors.Count;
for i := 0 to ErrorCount - 1 do begin
IError := IErrors.Item[i];
S := Format('error: %d, source: %s description: %s', [i, IError.Source, IError.Description]);
Memo1.Lines.Add(S);
end;
Caption := IntToStr(ErrorCount);
end;
end;
If I set AdoQuery1's Sql.Text to 'select * from anything' I get
error: 0, source: Microsoft OLE DB Provider for SQL Server description: Invalid object name 'anything'.
If you try it out, you should find that the contents of the Errors collection
is cumulative, but Errors has a Clear method to clear it.
See https://learn.microsoft.com/en-us/sql/ado/reference/ado-api/error-object?view=sql-server-2017
https://learn.microsoft.com/en-us/sql/ado/reference/ado-api/errorvalueenum?view=sql-server-2017
for more info (links courtesy of Remy Lebeau)