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DB2

Posted Feb 21, 2007

Using the FILLBY Method to Filter DB2 9 Data Sets...with a Twist

By Paul Zikopoulos

Since the middle of 2006, I’ve been writing about all the great integration features in IBM DB2 9 for the Microsoft Visual Studio 2005 integrated development environment (IDE) and the accompanying ADO.NET 2.0 API.

In an article called Binding DB2 Data to Visual Studio 2005 Windows Applications, I showed you how to quickly build a Windows application that binds various controls (ComboBoxes, DataGrids). In Build a DB2 Bound Data Application using Visual Studio 2005, I showed you an alternative way to even more quickly build a WinForm Windows application using a data grid that binds to your DB2 data server. You don’t specifically bind controls to an application: it’s even easier than that.

In this article, you can use either of those methods to build a new application, but I want to show you how to use a FILLBY method to pass dynamic parameters to the application, and then surprise you with a twist at the end.

The move from DataAdapters to TableAdapters

Although I didn’t spell it out in my previous DB2 9 and Visual Studio 2005 articles, the Visual Studio 2005 IDE adds a new helper class called a TableAdapter, which improves drag-and-drop application development. A TableAdapter is created automatically when you drag a data source from the Data Sources view onto a designer palette. The TableAdapter in Visual Studio 2005 replaces the DataAdapter that was part of Microsoft Visual Studio.NET 2003, which Microsoft has now deprecated in Visual Studio 2005.

One unique characteristic about TableAdapters is that they are not found in the .NET 2.0 Framework. Unlike typed data sets, which inherit from the System.Data.DataSet class, TableAdapters are entirely generated by Visual Studio 2005 using the data model you create with the Data Source Configuration Wizard, or in the Data Set Designer.

TableAdapters abstract the database type away from application code, which lends itself to more flexibility for application deployment. For example, let's say you have developed your application using SQL Server 2005. Later you decide to port that database to DB2 running on Linux, UNIX, or Windows. In the .NET 1.0 and .NET 1.1 Frameworks, which were integrated into Visual Studio.NET 2002 and Visual Studio.NET 2003, you would have had to change the object types you were using to access the database; in Visual Studio 2005, it’s a completely different (and more streamlined) story.

Building an application using the FILLBY method

To build an application using the FILLBY method in your application’s tool strip, perform the following steps:

1.  Create a new C# application, called MyFILLBYProject, by selecting File>New Project>Windows Application, selecting Visual Studio C# (which may be under Other Languages depending on how you set up your IDE), entering the name in the Name field, and clicking OK.

2.  Open the Server Explorer (by pressing Ctrl+Alt+S or by selecting View>Server Explorer from the menu bar), and select a table. (In my example, I selected the XTREME table, which I created in the SAMPLE database, but you can use any table you want.) View the properties of your table’s columns by selecting Properties from the right-click context menu and see if your table has a primary key.

A column that is defined as a table’s primary key has a 1 in the Primary Key property field, while a column that is not a primary key has a 0 (or may be blank).

 

For this article, the table you select doesn’t need a primary key because I’ll show you how to use the tool strip to filter data with a FILLBY method. However, if the table you select doesn’t have a primary key, you won’t be able to perform INSERT, UPDATE, and DELETE operations on this data. The DB2CommandBuilder uses a primary key for these types of data operations in order to build the corresponding statements that it uses to change the underlying table’s row.

It’s easy to understand this requirement when you think about it. A data set is a disconnected data persistence container. When the DataAdapter reconnects to the actual data server to process any data change requests, how can it be sure it will change the data for the row that was fetched? Using a primary key, of course! With a primary key, the DB2CommandBuilder can build a WHERE clause for the dirty row to ensure that it is positioned on the same row in the database as the data set. If there is no primary key, then the DB2CommandBuilder cannot guarantee it is positioned on the same row, and will not build statements to change data. You can, of course, work around this method if you know the metadata of the table and hand-generate these data manipulation statements (DML) yourself. However, we want a slick and easy solution, so if you plan to code any INSERT, UPDATE, and DELETE operations into your application, ensure that you have defined a primary key on the table where the data resides.

3.  Ensure that the Add Data Source view is displayed in Visual Studio 2005 by pressing Shift+Alt+Delete or selecting Data>Show Data Sources from the menu bar.

4.  Click Add New Data Source in the Data Sources view, select Database, and click Next:

5.  Select the SAMPLE database from the Which data connection should your application use to connect to the database? drop-down list.

6.  Select the Yes, include sensitive data in the connection string radio button, and click Next. (I’m assuming that you’re just working on your own test machine here and notice that Visual Studio 2005 collapses the Connection string box to hide these details from prying eyes.)

7.  Accept the defaults on the next pane of this wizard. Click Next.

8.  Expand the Tables toggle, select the table that you want to include in your application, and click Finish:

You can select multiple sources from your underlying data server to populate the disconnected data set. In the previous figure, I’ve added a single table called XTREME (and all of its columns). You could have multiple tables, or a combination of tables and views. In addition, you could even use a function or stored procedure to populate the data set. (I will show you this method in a future article.)

After you’ve added the data set, the Visual Studio 2005 IDE should look like this:

Note that your table has populated a data set in the Data Sources view. Expand it to see all of its contents if it isn’t automatically expanded for you.

9.  Use the left mouse button to select and drag two columns from your data set to your Windows Application form, and then resize the data grid so it looks like this:

10.  Now add a DataGridView to list all the data in the data set from Toolbox and bind it to the <your_table_name>BindingSource object such that the designer palette looks like this:

11.  Press F5 to build your application. It will look similar to this:



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