"Frnak McKenney" <frnak@far.from.the.madding.crowd.com> wrote in message
news:13ibjsnicudog1a@corp.supernews.com...
>
> I'm making changes to a small, portable, single-user database
> application I wrote a couple of years back built around a muli-table
> Access database and written in C# and .NET 1.1. Most of the changes
> are are minor, but one involves "subsetting" the database, that is,
> creating a new database file (.mdb) with a subset of the current
> database's rows. Read in a schema and some tables from one database
> / file, write them out to a brand new database / file. Right?
>
> Well, either I'm being incredibly dense, or this is an extremely
> non-trivial task. Since it's difficult for me to imagine that
> 'CREATE' support wouldn't be hidden _somewhere_ in .NET's OleDb
> support, I'm hoping that if I describe what I've tried someone will
> put me out of my misery with a few, well-chosen -- but helpful --
> comments on my obtuseness. <grin?>
>
> Reading tables from the original database ("Filling") into
> DataTables in a DataSet is fairly straightforward, and the 'web
> abounds with examples of how to do this. Creating a new DataSet
> with a duplicate schema isn't hard, either:
>
> DataSet dsClone = dsOriginal.Clone();
>
> followed by selected row-copies from the old to the new via
> DataViews:
>
> dsClone.Tables[tname].ImportRow( dv[i].Row );
>
> Then you open a connection to the new database-to-be:
>
> OleDbConnection connDb = new OleDbConnection();
> connDb.ConnectionString = DbConnString1
> + filename
> + DbConnString2;
> connDb.Open();
>
> Whoops!
>
> - If the file name doesn't already exist, you get an exception.
> - If the file exists but hasn't been Access-initialized, you get
> an exception ("wrong file structure" or something similar).
>
> So either there is a secret substring I need to include in my
> ConnectionString ("...Mode=Create;..." ?) to prepare the file for
> a CREATE-like operation, or the file structure has to be "built" /
> initialized prior to opening the Connection.
>
> There's got to be some step there that I'm overlooking.
>
> Hints would be appreciated. If I can't figure out how to do this, my
> fallbacks include:
>
> 1) Byte-copying the current .mdb file -- while it's open -- under a
> new name, opening ("connecting to") the new file, and then
> emptying some tables and chopping out rows from others (and
> maybe doing a compress-in-place on the result),
>
> 2) Adding an Empty-Db.mdb file ("...just the Schema, Ma'am") to the
> package that would only be used for subsetting the database,
> following the steps in option (1), or
>
> 3) Reverse-engineering the .mdb file structure and coding the
> creation of a new one "by hand". (No, I'm not serious -- or not
> entirely serious-- about this one, just frustrated enough to
> start thinking anlong those lines.)
>
> 4) Embedding a binary string containing a complete (but table-less)
> .mdb file into my applic... no, let's not go there. (But it
> _would_ be portable. <grin!>)
>
> Please, someone, point out to me that I've been repeatedly reading
> past an OleDbConnection.OpenNew() method that does exactly what I'm
> trying to do... or something along those lines! <grin>
>
>
> Frank McKenney
> --
> "The most amazing achievement of the computer software industry is
> its continuing cancellation of the steady and staggering gains
> made by the computer hardware industry..." -- Henry Petroski
> --
> Frank McKenney, McKenney Associates
> Richmond, Virginia / (804) 320-4887
> Munged E-mail: frank uscore mckenney ayut minds pring dawt cahm (y'all)