Using Constructors with Object Oriented Database Development with VB.NET 2005 - Defining constructors with parameters in a class

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Just like methods in a class, a constructor can also have parameters. This provides a great advantage sometimes when initializing objects with some values. Let us modify the constructor defined in the previous section as follows:

Public Class Emp

    Private m_empno As String
    Private m_ename As String
    Private m_sal As Double
    Private m_deptno As Integer
    Private m_errMsg As String

Public Sub New(ByVal empno As String, ByVal ename As String, ByVal sal As
Double, ByVal deptno As Integer)
        m_empno = empno
        m_ename = ename
        m_sal = sal
        m_deptno = deptno
        m_errMsg = ""
    End Sub
    ...
End Class

The above class is defined with a constructor with parameters. In the above case, we cannot simply create an object with the "new" keyword. The declaration of the object should look something like the following:

            Dim ep As New Emp("1001", "jag", 1000, 10)

The above statement creates and instantiates an object by calling the constructor with parameters. We can rewrite our code for "btnAdd_Click" as follows:

    Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnAdd.Click
        Me.lblErrMsg.Text = ""
        Try
            Dim ep As New Emp(Me.txtEmpno.Text, Me.txtEname.Text,
Me.txtSal.Text, Me.txtDeptno.Text)
            ep.add()
        Catch ex As Exception
            Me.lblErrMsg.Text = ex.Message
        End Try
    End Sub

Next: Constructor overloading within a class >>
 

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