Updating ms access database using vb net
Update(Data Set data Set, String src Table) at Learning ASPNET. 'For an Ole DBCommand, use question marks instead of naming the parmaters. Connection = cnn '------------------------------ '------------------------------ '~~~~Parameters: Adding to Command 'Add parameters to the Data Adapter Command object's parameters collection. Ole Db Data Adapter '------------------------------ '~~~~ Parametters: In SQL Statement, parameters are named, using a prefix of @. " Dim cmd Update As New Ole Db Command(str SQL) cmd Update. Parameters 'The last parameter in this overload of Add allows us to specify a column name to bind to . Once the program is running, click on the button you created; you should see a message that tells you that the connection to the database is open. You should be able to navigate backwards and forwards through the records in the table, or jump to the first or last records. Close this message box, and you should see another message box telling you that the connection is closed (if you get an error message, make sure that your database is in the location you specified). NET uses an object called a Data Set to hold information read from the database (alternatively, an object called a Data Table is available if you just want to read information, as opposed to writing new or modified information to the database). The next step will be to add controls to allow us to add, delete or update records. Close() Msg Box("The connection to the database is now closed.") Your coding window should now look like the illustration below. Visual Basic will create an empty procedure for you, as before). You can run the program now to check that it can open and close the database. inc = max Rows - 1 Navigate Records() Run the programme to test the navigation buttons. On the updating, it did beatifully; for example, when I change the Unit Price or Unit In Stock of a particular product, it updated correctly.
This second parameter is optional, but may make the code more readable. You can test the Add Record button by running the program and trying it out. Delete() max Rows = max Rows - 1 inc = 0 Navigate Records() da. If the user clicks on the Yes button, the code that follows the statement will be executed (i.e. If the user clicks on the No button, the delete operation will be cancelled.If this is not the case, an attempt to add or update records may cause problems, as you will need con. Open() Msg Box("A connection to the database is now open.") con. To String() End Sub The code so far should look like the illustration below. We will now add the code for the Previous Record button (switch to the form design window again, and double-click the Previous Record button. We will also need to create string variables to hold the commands we will be sending to the database. Remember that rows and columns are indexed from zero, and that the first column in the table is the Contact ID field, which we are not currently interested in. These will be written in Dim ds As New Data Set Dim da As Ole Db. If you run the program and click on the button (just click on OK when the connection status messages are displayed, to get rid of the message boxes), you should see the name "Chris Wells" displayed in the two text boxes. OLEDB.12.0; Data Source=Contacts.accdb; Persist Security Info=False;" con. Close() Private Sub Navigate Records() txt First Name. Using the same database (Contacts.accdb) as for the page "An Address Book Database", we will create a database application using Visual Basic program code rather than wizards. The connection string identifies the version of Jet to be used, which will depend on the version of Microsoft Access used to create the database. As an exercise, think about how to the program's code could be amended to prevent the possibility of this occurring. The database we are using was created with Access 2007, so the version used is ACE 12.0. We will now look at the code needed to add a new record. There is one minor problem, which occurs if you click on the Update Record button before the first record has been displayed in the form (try this for yourself to see what happens). We will now look at the code needed to delete a record. As an exercise, see if you can amend the code to eliminate any potential problems. As a final exercise, you may wish to complete the program by adding the requisite text boxes and labels, and generally improving the look and feel of the user interface. When you re-open the application, you should find that the changes you made have been saved. As an exercise, try to identify what circumstances cause an error, and try and amend your code to eliminate any problems. As with the previous code we have written, you will probably find that under certain circumstances, use of the Delete Record button causes a problem. The application is obviously far from complete, since at the moment it displays only the first and last names of the contact.In order to see a different record, we need to use a different row number. Open() sql = "SELECT * FROM Contact" da = New Ole Db. In fact, we can scroll through the entire table by incrementing the row number to view each record in turn.