The following procedures describe how to build a dbExpress database application.
Building a VCL Forms dbExpress.NET application consists of the following major steps:
- Set up the database connection.
- Set up the unidirectional dataset.
- Set up the data provider, client dataset, and data source.
- Connect a DataGrid to the connection components.
- Run the application.
To add a dbExpress connection component
- Choose FileNewVCL Forms Application. The VCL Forms Designer displays.
- From the dbExpress category of the Tool Palette, place a TSQLConnection component on the form.
- Double-click the TSQLConnection component to display the Connection Editor.
- In the Connection Editor, set the Connection Name list to IBConnection.
- In the Connections Setting box, specify the path to the InterBase database file called employee.gdb in the Database field. By default, the file is located in C:\Program Files\Common Files\CodeGear Shared\Data.
- Accept the value in the User_Name field (sysdba) and Password field (masterkey).
- To test the connection, click the button with the checkmark on it (just above the Connection Name list).
Note: By default, you are prompted to log in. Use the masterkey password. If the connection works a confirmation message appears. If you cannot connect to the database, make sure you have installed Interbase and that the server is started.
- Click OK to close the Connection Editor and save your changes.
To set up the unidirectional dataset
- From the dbExpress category of the Tool Palette, place a TSQLDataSet component at the top of the form.
- In the Object Inspector, set the SQLConnection property drop-down list to SQLConnection1.
- Set the CommandText to a SQL command, for example, Select * from sales. For the SQL command, you can either type a Select statement in the Object Inspector or click the ellipsis to the right of CommandText to display the Command Text Editor where you can build your own query statement.
Tip: If you need additional help while using the Command Text Editor, click the Help button or press F1.
- In the Object Inspector, set the Active property to True to open the dataset.
To add the provider
- From the Data Access category of the Tool Palette, place a TDataSetProvider component at the top of the form.
- In the Object Inspector, set the DataSet property drop-down list to SQLDataSet1.
To add client dataset
- From the Data Access category of the Tool Palette, place a TClientDataSet component to the right of the DataSetProvider component on the form.
- In the Object Inspector, set the ProviderName drop-down to DataSetProvider1.
- Set the Active property to True to allow data to be passed to your application.
A data source connects the client dataset with data-aware controls. Each data-aware control must be associated with a data source component to have data to display and manipulate. Similarly, all datasets must be associated with a data source component for their data to be displayed and manipulated in data-aware controls on the form.
To add the data source
- From the Data Access category of the Tool Palette, place a TDataSource component to the right of the ClientDataSet on the form.
- In the Object Inspector, set the DataSet property drop-down to ClientDataSet1.
To connect a DataGrid to the DataSet
- From the Data Controls category of the Tool Palette, place a TDBGrid component on the form.
- In the Object Inspector, set the DataSource property drop-down to DataSource1.
- Save all files in the project.
- Select RunRun. You are prompted to enter a password.
- Enter masterkey as the password. The application compiles and displays a VCL.NET form with a DBGrid.