CIS 338: Using ADO (ActiveX Data Objects) [largely replaced by adonet.vb] Dr. Ralph D. Westfall April, 2003

Universal Data Access ADO.NET is part of Microsoft's universal data access strategy Universal Data Access FAQs ODBC: open database connectivity API standard for using relational databases  API = application programming interface  includes "drivers" for Access, dBase, DB2, Excel, text, etc.drivers Microsoft is leading ODBC backer

Universal Data Access - 2 OLEDB: DB object linking & embedding next step beyond ODBC accesses relational databases with ODBC provides access to other data also  , video, voice, images, web pages, etc., etc.  data is accessed "in place" (no need to first move it into a database)

OLEDB Concepts data store = "persistent" collection of data data provider = gets data from data store OLEDB "driver": database, data, etc. OLEDB "has nothing to do with Object Linking and Embedding" (Word, Excel) data consumer = application that uses data ADO (ActiveX Data Object) interfaces to data store through OLEDB

ADO.NET replaceS DAO, RDO and previous ADO can use ADO.NET with VB in code via object interface  more powerful than DAO and previous ADO  numerous objects with useful properties and methods

OLEDB with ADO.NET dataset object copy of data in memory, rather than connected to the database can have 1 to many DataTable objects ADO.NET OLEDB data providers SQLClient driver for SQL Server (Microsoft) OleDBClient driver for other databases

DataSet Object Data Tables "collections" of table(s) information rows, columns of table relationships with other tables constraints to manage additions/deletions from tables that are related to other tables data "views" that allow data to be seen in different ways than it is stored in table(s)

Data Provider Objects connection (to file or server) command object runs SQL or stored procedures in the database data reader (if need high performance) read only, forward only data adaptor (more capabilities) add, change, delete, relate tables

ADO.NET: XML Data Transfer industry standard for transferring data like HTML, but can create other tags HTML: [some text] XML: [value for price] like HTML, can have tags within others HTML: XML:

XML Schema separate file that describes data in an XML file type of data: numeric, text, etc. occurrences: 0 or 1, or either to many relationships e.g., name includes 1 st and last names other characteristics e.g., primary key

Exercise create your own tags for something you are familiar with food, pets, motor vehicles, video games, ways to communicate, college courses, etc. make sure that tags are "nested" open and close inside other "boxes" then fill in with some sample data

Database System Options SQL Server high performance not well-suited for using on one computer Microsoft Data Engine (MSDE) chopped down version of SQL Server can work with SQL Server files but also can work with Microsoft Access

Creating an MSDE Database note: may have problems on network start Access File>New, New>Project (New Data) Access creates a MSDE database (.adp) data storage is different, but you can work with it like an Access database (.mdb) can edit data or upload files as with.mdb

Connecting ADO to Access start a new.NET Windows application View>Server Explorer right click Data Connections>Add Connection click Provider tab>Microsoft Jet 4.0 OLE DB Provider>Next button browse … for Access database>OK

Using Data Connection viewing data in a table in Server Explorer, expand Data Connections, Access, Tables icons right click on a Table>Retrieve Data from Table close this preview window

Create a DataAdapter in Server Explorer, click and drag a Table onto the form note 2 new components in tray below right click DataAdaptor>Generate Dataset

DataGrid with DataAdapter add a DataGrid set DataSource property to DataSet in Form_Load, use.Fill method of DataAdapter with DataSet as argument Click Start to view DataGrid

List/ComboBox with DataSet drag/drop ListBox onto form set DataSource to DataSet (drop down) set DisplayMember to a field in table add.Fill method of DataAdapter see previous slide if didn't do this already note that data is in same order as in database (not sorted)

DataView List/ComboBox DataView makes it possible to sort and do other things with database data drag/drop DataView object to form/tray set DataView Table property to a table from the DataSet (drop down) type in a field name for Sort property see field names in Server Explorer

DataView List/ComboBox - 2 drag/drop ComboBox onto form set DataSource to DataSet (drop down) set DisplayMember to a field in table add.Fill method of DataAdapter see previous slide if didn't do this already can set.ListIndex property to -1 so that no item is selected at start (ListBox too)

SQL as Source of Data expand DataAdaptor Select Command property to see CommandText code can modify this SQL by changing the line, or by clicking … to see Query Builder can (un)select fields in Output column can add a WHERE condition value ? in the Criteria column(s) prompts user

Binding Other Controls to Data draw TextBox or Label on form expand (DataBindings) property click Text, and select table/field from drop down add code to load DataSet with just the item input or selected in another control

Binding Other Controls - Code

Setting Up ADO with a DSN Windows (not VB): Start>Settings>Control Panel[>Administrative Tools>Data Sources] click Data Sources (32 bit) [User DSN tab] select MS Access Database, click Add select Microsoft Access Driver, click Finish click select, choose database (e.g., BIBLIO) type in Data Source Name (DSN) and description, then click OK  put in what you want to call DSN, your description

Using ADO Data Control right click toolbox, select Components click Microsoft ADO Data Control 6.0, OK click Adodc control on toolbar, draw on form right click on control to see Properties page first set up Source of Connection (General tab) select Use ODBC Data Source Name and select the DSN you just created (or Use Connection String>Build etc. with latest Microsoft Jet [=Access] Provider)

Using ADO Data Control - 2 select RecordSource tab select 1 of following Command Types: adCmdText – need to type in SQL query adCmdTable – need to select the table name adCmdStoredProcedure – need to select the procedure name enter SQL, or select Table or stored procedure (e.g., Publishers), click OK

Using ADO Data Control - 3 add controls (e.g., 2 textboxes) to form bind controls to data fields (like with DAO; e.g., Name, City) set DataSource properties = name of data control from dropdown list set DataField properties to field names from dropdown list run project, scroll with ADO data control

Using Code & ADODC Control 'command button event code (need a 3 rd 'textbox to run this) Dim sState as String, sSQL as String sState = Text3.Text '3 rd TextBox sSQL = "select * from Publishers" If sState <> "" Then sSQL = sSQL & _ " WHERE State = '" & sState & "'" 'space Adodc1.CommandType = adCmdText Adodc1.RecordSource = sSQL Adodc1.Refresh

Data Grid Control displays database data on a form like in a spreadsheet can use this layout to edit data in the database

Using DataGrid Control right click toolbox, select Components click Microsoft ADO Data Control 6.0 click Microsoft Data Grid Control 6.0, OK click Adodc control on toolbar, draw on form right click on Adodc control to see Properties 1st set Source of Connection (General tab) select Use ODBC Data Source Name and select DSN (BIBLIO), or use connect string select RecordSource tab select Command Type (adCmdTable), select Table name (Publishers)

Using DataGrid Control - 2 click toolbar's DataGrid, draw on form using regular Properties window, set DataSource to connection being used then right click on DataGrid, select Retrieve fields

Using DataGrid Control - 3 DataGrid properties use regular Properties window to set some properties  e.g., Caption right click on grid for Properties Pages for others General tab  ColumnHeaders – on or off  Enabled – allows user to scroll, select, modify  AllowAddNew, AllowDelete, or AllowUpdate – user can add, delete, or change database contents

Using DataGrid Control - 4 Properties Pages (continued) Keyboard tab allow use of arrow keys set TabAction tab key behavior (reference)reference other tabs Color, Font, Format (number, date/time, + etc. like in Excel)

Editing a DataGrid right click grid, select Edit, right click again use commands to change grid  cut, paste, delete, etc. can split a grid to get a new user window  use Property Pages Layout tab to uncheck Visible for individual columns in different splits

Using ActiveX Data Objects Project>References> and then check: Microsoft ActiveX Data Objects 2.x Library  e.g., x = 2.7 if you have it provides ADOR (recordset) objects  Recordset, Field and Property objects provides ADODB objects  above objects plus Connection, Command, Parameter and Error objects

Set Up a Data Source in Code can use a connection object to access a database with a DSN Dim cn As ADODB.Connection Set cn = New ADODB.Connection cn.ConnectionString="DSN=[name]" cn.Open

Setting Up a Data Source - 2 connecting without a DSN (p. 629) Dim cn As ADODB.Connection '(General) Set cn = New ADODB.Connection cn.ConnectionString = _ "Driver=Microsoft Access Driver (*.mdb);DBQ=C:\[path]\[file].MDB;" 'need just one space before (*.mdb) 'NO spaces!! in Driver=Microsoft... cn.Open

Using Recordsets in Code Dim cn As ADODB.Connection Dim rs[name] As ADODB.Recordset 'add to (General Declarations) Set cn = New ADODB.Connection cn.ConnectionString = _ "Driver=Microsoft Access Driver (*.mdb);DBQ=C:\[path]\[file].MDB;" cn.Open

Using Recordsets in Code - 2 Const sSQL = "SELECT * FROM [table]" Set rs[name] = New ADODB.Recordset rs[name].ActiveConnection = cn rs[name].Source = sSQL rs[name].Open rs[name].MoveFirst Print "[ ]= " & _ rs[name].Fields("[field]")

Multiple Ways to Use Objects Set rs[name] = New ADODB.Recordset rs[name].ActiveConnection = cn rs[name].Source = sSQL rs[name].Open OR Set rs[name] = cn.Execute(sSQL)

Recordset Lock Types rs[name].LockType = … adLockReadOnly – can't add, change, or delete adLockPessimistic – record locked while working on it adLockOptimistic – record locked when submitted to database (but rejected if another user already has a lock on it) adLockBatchOptimistic – multiple records submitted, locked individually while being updated

Recordset Cursor Types rs[name].CursorType = … adOpenForwardOnly – fast, but one-way adOpenKeySet – user can see changes by other users, but not new records or deletions adOpenDynamic – slowest, but user can see all modifications by other users adOpenStatic – can't see any modifications

Updating Databases with Recordsets in ADO Set rs[name] = New ADODB.Recordset rs[name].CursorType = [ ] rs[name].LockType = [ ] rs[name].Source = [table, SQL] rs[name].ActiveConnection = cn rs[name].Open

Updating Databases with Recordsets in ADO - 2 'changing field values rs[name].Fields("[field]") = [ ] rs[name].Update '1 command 'need 2 commands to change in DAO 'adding new records (2 commands) rs[name].AddNew '1 st command rs[name].Fields("[field]") = [ ] rs[name].Update '2 nd command

Disposing of Objects to conserve resources, get rid of objects when finished with them rs[name].Close 'disconnects from database Set rs[name] = Nothing 'removes from memory cn.Close Set cn = Nothing

Data Source Name (DSN) DSNs allow you to set up "virtual addresses" on a computer DSN "points to" the actual physical path  can change physical path for a DSN (e.g., when move application to another computer) but use same DSN in code DSNs can make applications more portable but DO NOT use DSNs in your projects for CIS 338 (they are not on my computer!)