Copy TDataSet to XLS via ADO - excel

Question

I'm trying to copy the content from a TDBGrid to an Excel file using an ADO connection to transfer the data. This works for values that are <= 255 characters but fails for longer strings. What can I do to copy strings that are longer than 255 characters?
Changing the DataType to adLongVarWChar tbl.Columns.Append doesn't work. The ADOQuery gets a varchar field with Size 255 regardsless what I use when I create the table.
procedure DBGridToExcelADO(DBGrid: TDBGrid; FileName: string; SheetName: string);
var
cat : _Catalog;
tbl : _Table;
col : _Column;
i : integer;
ADOConnection : TADOConnection;
ADOConnectionExcel: TADOConnection;
ADOQuery : TADOQuery;
ScrollEvents : TScrollEvents;
SavePlace : TBookmark;
begin
//exporting
ADOConnectionExcel := TADOConnection.Create(nil);
try
ADOConnectionExcel.LoginPrompt := False;
ADOConnectionExcel.ConnectionString := 'Provider=Microsoft.Jet.OLEDB.4.0; Data Source=' + FileName + ';Extended Properties=Excel 8.0';
ADOConnectionExcel.Open;
//WorkBook creation (database)
cat := CoCatalog.Create;
cat._Set_ActiveConnection(ADOConnectionExcel.ConnectionObject);
//WorkSheet creation (table)
tbl := CoTable.Create;
tbl.Set_Name(SheetName);
//Columns creation (fields)
DBGrid.DataSource.DataSet.First;
with DBGrid.Columns do
begin
for i := 0 to Count - 1 do
if Items[i].Visible then
begin
col := nil;
col := CoColumn.Create;
with col do
begin
Set_Name(Items[i].Title.Caption);
Set_Type_(adVarWChar);
end;
//add column to table
tbl.Columns.Append(col, adVarWChar, 20);
end;
end;
//add table to database
cat.Tables.Append(tbl);
col := nil;
tbl := nil;
cat := nil;
//exporting
ADOConnection := TADOConnection.Create(nil);
ADOConnection.LoginPrompt := False;
ADOConnection.ConnectionString := 'Provider=Microsoft.Jet.OLEDB.4.0; Data Source=' + FileName + ';Extended Properties=Excel 8.0';
ADOQuery := TADOQuery.Create(nil);
ADOQuery.Connection := ADOConnection;
ADOQuery.SQL.Text := 'Select * from [' + SheetName + '$]';
ADOQuery.Open;
DisableDependencies(DBGrid.DataSource.DataSet, ScrollEvents);
SavePlace := DBGrid.DataSource.DataSet.GetBookmark;
try
with DBGrid.DataSource.DataSet do
begin
First;
while not Eof do
begin
ADOQuery.Append;
with DBGrid.Columns do
begin
ADOQuery.Edit;
for i := 0 to Count - 1 do
if Items[i].Visible then
begin
//Fails if Length > 255
ADOQuery.FieldByName(Items[i].Title.Caption).AsString := FieldByName(Items[i].FieldName).AsString;
end;
ADOQuery.Post;
end;
Next;
end;
end;
finally
DBGrid.DataSource.DataSet.GotoBookmark(SavePlace);
DBGrid.DataSource.DataSet.FreeBookmark(SavePlace);
EnableDependencies(DBGrid.DataSource.DataSet, ScrollEvents);
ADOQuery.Close;
ADOConnection.Close;
ADOQuery.Free;
ADOConnection.Free;
end;
finally
if Assigned(ADOConnection) and ADOConnection.Connected then ADOConnectionExcel.Close;
ADOConnectionExcel.Free;
end;
end;

Answer 1

You can use TJvDBGridExcelExport JVCL coming in the Jedi (www.delphi-jedi.org/). I have used this with good results, and this is opensource.