form1.vb

数据库学习的绝好例子简单的数据库经典入门

Imports System.Data

Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles MyBase.Load

        'Initialize a new instance of the data access base class
        Using objData As New WDABase
            Try
                'Declare local variables
                Dim objDataTable As New DataTable("Projects")

                'Get all Projects in a DataSet
                objData.SQL = "SELECT ProjectID, ProjectName " & _
                    "FROM vw_SelectProjects " & _
                    "ORDER BY ProjectName"
                objData.InitializeCommand()
                Call objData.FillDataTable(objDataTable)

                'Bind ListBox control
                ListBox1.DataSource = objDataTable
                ListBox1.DisplayMember = "ProjectName"
                ListBox1.ValueMember = "ProjectID"

            Catch ExceptionErr As Exception
                MessageBox.Show(ExceptionErr.Message, "Exercise 1")
            End Try
        End Using
    End Sub

    Private Sub ListBox1_Click(ByVal sender As Object, _
        ByVal e As System.EventArgs) Handles ListBox1.Click

        'Initialize a new instance of the data access base class
        Using objData As New WDABase
            Try
                'Build the SQL string
                objData.SQL = "SELECT ProjectDescription " & _
                    "FROM vw_SelectProjects " & _
                    "WHERE ProjectID = @ProjectID"

                'Initialize the Command object
                objData.InitializeCommand()

                'Add a Parameter to the Parameters collection
                objData.AddParameter("@ProjectID", _
                     Data.SqlDbType.UniqueIdentifier, 16, ListBox1.SelectedValue)
                'Open the connection
                objData.OpenConnection()

                'Get the data in a DataReader object
                objData.DataReader = objData.Command.ExecuteReader

                'See if any data exists before continuing
                If objData.DataReader.HasRows Then

                    'Read the first row
                    objData.DataReader.Read()

                    'Populate the fields on the form
                    txtProjectDescription.Text = _
                        objData.DataReader.Item("ProjectDescription")

                End If

                'Close the DataReader
                objData.DataReader.Close()

                'Close the database connection
                objData.CloseConnection()

            Catch ExceptionErr As Exception
                MessageBox.Show(ExceptionErr.Message, "Exercise 1")
            End Try
        End Using
    End Sub
End Class