An Introduction to Object Oriented Database Development with VB.NET 2005
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This article introduces you to object oriented programming for database development using Visual Basic.NET 2005. It explains classes, fields, methods, and objects.
A downloadable file for this article is available
here.
For this article, I assume that you know enough about the basics of working with VB.NET controls, ADO.NET, and so forth using Visual Basic.NET 2005. Even though this article only covers the basics of object-oriented programming along with database development, I shall extend it in the form of a series to cover the most advanced topics in Visual Basic.NET 2005. You do not need to be familiar with OOP to understand this article.
The entire source code for this article is available at the link indicated above in the form of a downloadable zip file. The solution was developed using Microsoft Visual Studio 2005 Professional Edition with Microsoft SQL Server 2005 Developer Edition on Microsoft Windows Server 2003 Enterprise Edition. Even though I believe that the source code available with this article can work with Microsoft Visual Studio.NET 2003/2002, I didn’t really test it in any other environment. I request that you post in the discussion area if you have any problems with execution.
To make this article simple, I created a sample database named “sample,” with a table “emp” containing the columns empno (string), ename (string), sal (double) and deptno (integer) and a few rows.
Developing database interactions in a separate class: source code
Once you open the downloadable solution, you will be able to find a file named “emp.vb” in the solution explorer. Double click on it to open and you will find the following source code in it:
ImportsSystem.Data.SqlClient
PublicClass Emp
Public m_empno As String
Public m_ename As String
Public m_sal As Double
Public m_deptno As Integer
Public Sub load(ByVal empno As String)
m_empno = empno
Dim cn As New SqlConnection("Data Source=.sql2k5;initial catalog=sample;user id=sa;password=eXpress2005")
Dim cmd As New SqlCommand("select * from sample.dbo.emp where empno='" & empno & "'", cn)
cmd.Connection.Open()
Dim rd As SqlDataReader = cmd.ExecuteReader
rd.Read()
m_ename = rd("ename")
m_sal = rd("sal")
m_deptno = rd("deptno")
cmd.Connection.Close()
cmd.Dispose()
cn.Dispose()
End Sub
EndClass
To access the same class, I designed a small form with four text boxes (for empno, ename, sal and deptno) and a few buttons. The code for the button “search” is given below:
PrivateSub btnSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSearch.Click
Dim ep As New Emp
ep.load(Me.txtEmpno.Text)
Me.txtDeptno.Text = ep.m_deptno
Me.txtEname.Text = ep.m_ename
Me.txtSal.Text = ep.m_sal
End Sub
I shall explain the above code in the next section.
Next: Explaining the class >>
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