Test

VB.NET – Database Connection

What we will learn today:

Creating a new database

Database connection using oledb

Retrieving data from database

Manipulating data in database from VB.NET application

Creating New Database and Table

Open your SQL Server Management Studio, and connect to your database engine {draw:frame}

After connecting, the screen will show you something like this {draw:frame}

We will create a new database, expand the ‘Databases’ folder, then right click on it, the choose ‘new database’ {draw:frame}

Type a new name for your database ‘forHCI’, and click ok (we will leave everything else by default)

Your new database should be created and shown in the object explorer.

{draw:frame}

Expand it and right click on the ‘tables’ folder and choose ’new table’. Type in three new column named ‘id_barang’, ‘nama_barang’, and ‘harga’, just like the screenshot below. {draw:frame}

Save your new table by clicking the save icon, name it ‘barang’. {draw:frame}

We want to fill the table for initial data to work with in the VB.NET application. Right click on the table ‘barang’ and choose ‘edit top 200 rows’, and type in some data. {draw:frame}

Alternatively you can insert data into the table from the query. You can open a new query window by clicking ‘new query’ button.

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{draw:frame}

Then type in insert query in the query window

{draw:frame}

The tables are ready for our practice. Database Connection

We will use the previous project (last week, MDI form) or alternatively you can create a new project.

If you use the previous project, create a new menu item and a new form and name it ‘database’ then add some sub menu item ‘Retrieve’ and ‘Insert Update Delete’

{draw:frame}

Create two new forms ‘frmretrieve’ and ‘frminsupdel’ and link it to the new menu item

Add a new control called ‘OleDbConnection’ from the toolbox and click anywhere on form1 or mainform

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You should see something like this in your form1 or mainform {draw:frame}

Next, we want to set the connection to the database we just created. Click on the oledbconnection1 in the above screenshot, and look for ‘ConnectionString’ property in the properties, then click on the dropdown arrow and choose ‘new connection’ {draw:frame}

You should see a new form like below. {draw:frame}

Type in or choose the server name you use, choose ‘use windows authentication’, then select the database name we just created ‘forHCI’. Click ‘test connection’, if you do it right, it will tell you that the connection succeeded. Click ‘Ok’ to proceed.

Database connection is ready for use. Retrieving Data from Database

Open the ‘frmretrieve’

Design the form like the screenshot below

{draw:frame}

Name the textbox : txtId, txtNama, txtHarga Name the buttons : btnPrev, btnNext

We want to query our database and fetch the data from table ‘barang’ to the datatable. Double click on the form to create form load event handler

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Type in these codes

{draw:frame}

String sql is used to contain our query

Datatable is like a virtual table in your VB.NET, can be filled with any data, including data from a table from database

Dataadapter is like a bridge between the connection object (in this case, the oledbconnection1 we put in the form1 before) and the datatable (in this case, dt)

da.fill(dt), is used to fill the data queried from the database to the datatable

da.dispose() is like freeing a connection

Next, we want to display the data from datatable to the textboxes. Type in these codes just below the previous codes {draw:frame}

We can access the data in the datatable by the syntax:

datatable_name.Rows(row_index)(column_index)

in the example above, dt.rows(0)(1) means we point to the data stored in the datatable ‘dt’, in the first row, and second column.

Save your project and run it.

Next we want to put the data we queried to a datagridview. Type in these codes inside the form load sub procedure

{draw:frame}

Save your project and run it.

For exercise, try to make the next and previous button works. When user can navigate through the data in the datatable by clicking the next (>) and previous button (