Free Online Visual Basic Training course | Data Projects, Data Control and Environment

The Data control stores a Recordset of data from the original source (e.g. an Access database). A Recordset is a sub-set of the whole data store, which meets particular criteria. If, for example, you specified that you wanted to see all entries in a database where the "name" field was "John", the result would be a Recordset of several entries, but all of them would be called "John". In this way, we can search through large amounts of data for a particular entry.

Navigation through a given Recordset is then done with the transport buttons within the Data control itself.

The following exercise guides you through the construction of a simple data form. Initially, the Recordset contains all of the data in the original source (an Access database).

Exercise xx:
You should be supplied with an Access database before beginning this exercise.

Create a new "Standard EXE" project in Visual Basic. Add a Frame, a CommandButton and a Data control to the Form. Insert Label controls into the Frame to match the following form:

Note: Note that all of the Label controls within the Frame are standard Label controls that have had their "ForeColor" and/or "BackColor" properties changed.

The CommandButton has had it's "Caption" property changed to "E&xit" and the Data control has had it's "Caption" property changed to "Employees".

Select the Data control and modify it's "DatabaseName" property to the path to the Access database you have been supplied with (you can 'browse' to the file by clicking the little button (".") that appears hen you select this property).
The "RecordSource" property of the Data control must then be set to control the source of the data within the database. We will use an SQL query statement to determine the records that we want to use. Type the following SQL statement into the "RecordSource" property:

SELECT * FROM Employees

Each of the field Labels (the ones shown beginning with a '#' symbol) on the Frame must then be set up to use the Data control as their source. The other Labels are static descriptions of the fields being viewed.
For each of the Labels, change the "DataSource" property to the name of your Data control ("Data1") and the "DataField" property to the field associated with the Label (see the description label beside each one). In both cases, Visual Basic will suggest possible options in a drop-down style list when you select the property.
Enter some code into the CommandButton's Click Event method to unload the form when the user clicks "Exit".

Run the project and verify that you can navigate through the "Employees" field using the Data Control's buttons.

How could you modify the project so that the user could search for a specific employee by name? Test your theory.

12.2 Data Environment and Data Reports

The Data Environment acts as the Data source, like the Data control in the previous exercise. A Data Report can then be attached to this Data Environment and used to preview and print the records required.

Exercise xxi:

Re-Open the project in the previous exercise and add both a "Data Environment" and a "Data Report" from the "Project" menu.
On the Data Environment we are going to create a connection to our database. Expand the "Connections" folder in the Data Environment. Right-click on the default Connection called "Connection1" and select the "Properties." option on the pop-up menu.
On the dialogue box, select "Microsoft Jet 3.51 OLE DB Provider" under the "Provider" tab, then click "Next".
On the "Connection" tab, browse to the database or type the path into the box. Click the "Test Connection" button. If the connection fails, repeat the last two steps to connect to the database.
Click "OK" on the dialog box.
Right-click on the "Commands" folder in the data Environment and select "Add Command" from the pop-up menu. This should create a new Command called "Command1" inside the "Commands" folder.
Right-click on "Command1" and select "Properties." from the pop-up menu. A dialog box should appear. On the "General" tab of the dialog, change the value of the "Connection" to "Connection1".
Change the value of "Database Object" to "Table" and "Object Name" to "Employees". Click "OK" to accept the command.

Note: Notice that the Command now has sub-members, each one representing a field in the "Employees" table.

Open the Data Report and change the "DataSource" property to "DataEnvironment1" and the "DataMember" property to "Command1", to match those created in the Data Environment.
Drag-and-drop the sub-members (i.e. the fields) of Command1 onto the "Detail" section of the Data Report where you want them to appear. Give the Data Report a title caption using the RptLabel control from the toolbox.
Save and close the Data Report and Data Environment.
Open the form into the Object View window. Make space for and insert a new CommandButton. Label the CommandButton "&Report" and edit the CommandButton's Event method to display the Data Report as follows:

DataReport1.Show

Test your application.

Note: Note that the Data Report automatically caters for printing to the Windows System printer, making report generation much simpler.

12. Data Projects

12.1 Using the Data control

12.2 Data Environment and Data Reports