如何使用vb.net与Access数据库链接座位预订项目

Question

我有一个座位预定代码，但我不知道如何将其与访问数据库链接。我将按钮用作座位，因此当选择座位时，座位会隐藏起来，因此当我选择座位时，我需要帮助。座位号显示在访问数据库中。这是我的代码：

Public Class Form1
    Dim seatnumber As char
    Private Sub BTNA1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BTNA1.Click
        seatnumber = "A1"
        Confirmseat()
    End Sub

    Private Sub BTNA2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BTNA2.Click
        seatnumber = "A2"
        confirmseat()
    End Sub

    Private Sub BTNA3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BTNA3.Click
        seatnumber = "A3"
        Confirmseat()
    End Sub

    Private Sub BTNA4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BTNA4.Click
        seatnumber = "A4"
        Confirmseat()
    End Sub

    Private Sub BTNA5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BTNA5.Click
        seatnumber = "A5"
        Confirmseat()
    End Sub

    Private Sub BTNA6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BTNA6.Click
        seatnumber = "A6"
        Confirmseat()
    End Sub

    Private Sub BTNB7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BTNB7.Click
        seatnumber = "B7"
        confirmseat()
    End Sub

    Private Sub BTNB8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BTNB8.Click
        seatnumber = "B8"
        confirmseat()
    End Sub

    Private Sub BTNB9_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BTNB9.Click
        seatnumber = "B9"
        confirmseat()
    End Sub

    Private Sub BTNB10_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnb10.Click
        seatnumber = "B10"
        confirmseat()
    End Sub

    Private Sub BTNB11_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnb11.Click
        seatnumber = "B11"
        confirmseat()
    End Sub

    Private Sub BTNB12_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnb12.Click
        seatnumber = "B12"
        confirmseat()
    End Sub

    Public Sub confirmseat()
        Dim intresult As Integer
        intresult = MessageBox.Show("you selected" & seatnumber, "CONFIRM", MessageBoxButtons.YesNo, MessageBoxIcon.Question)
        If intresult = Windows.Forms.DialogResult.No Then
            seatnumber = "NO"
        Else
            Select Case (seatnumber)
            Case "A1"
                BTNA1.Visible = False
            Case "A2"
                BTNA2.Visible = False
            Case "A3"
                BTNA3.Visible = False
            Case "A4"
                BTNA4.Visible = False
            Case "A5"
                BTNA5.Visible = False
            Case "A6"
                BTNA6.Visible = False
            Case "B7"
                BTNB7.Visible = False
            Case "B8"
                BTNB8.Visible = False
            Case "B9"
                BTNB9.Visible = False
            Case "B10"
                btnb10.Visible = False
            Case "B11"
                btnb11.Visible = False
            Case "B12"
                btnb12.Visible = False
            End Select
            MessageBox.Show("Seat" & seatnumber & "is confirmed", "confirmation")
        End If
    End Sub

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim seatavailability As Integer
        If seatavailability <> "12" Then
            BTNA1.Visible = True
            BTNA2.Visible = True
            BTNA3.Visible = True
            BTNA4.Visible = True
            BTNA5.Visible = True
            BTNA6.Visible = True
            BTNB7.Visible = True
            BTNB8.Visible = True
            BTNB9.Visible = True
            btnb10.Visible = True
            btnb11.Visible = True
            btnb12.Visible = True

            Dim i As Integer
            Dim reservedseats(1) As Char
            For i = 0 To 12
                Select Case (reservedseats(1))
                    Case "BTNA1"
                        BTNA1.Visible = False
                    Case "BTNA2"
                        BTNA2.Visible = False
                    Case "BTNA3"
                        BTNA3.Visible = False
                    Case "BTNA4"
                        BTNA4.Visible = False
                    Case "BTNA5"
                        BTNA5.Visible = False
                    Case "BTNA6"
                        BTNA6.Visible = False
                    Case "BTNB7"
                        BTNB7.Visible = False
                    Case "BTNB8"
                        BTNB8.Visible = False
                    Case "BTNB9"
                        BTNB9.Visible = False
                    Case "BTNB10"
                        btnb10.Visible = False
                    Case "BTNB11"
                        btnb11.Visible = False
                    Case "BTNB12"
                        btnb12.Visible = False
                End Select
            Next
        End If
    End Sub

    Private Sub btncontinue_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btncontinue.Click
        Me.Close()
    End Sub

结束班级

Answer 1

请注意，您有很多重复的代码。您可以通过编写将按钮转发到ConfirmSeat的单个按钮单击处理程序来简化代码：

Private Sub ClickHandler(sender As Object, e As EventArgs)
    Dim seatNumber = Mid(DirectCast(sender, Button).Name, 4)
    ConfirmSeat(seatNumber)
End Sub

并按如下所示编写ConfirmSeat：

Private Sub ConfirmSeat(seatNumber As String)
    Dim result As Integer
    result = MessageBox.Show("you selected" & seatnumber, "CONFIRM", MessageBoxButtons.YesNo, MessageBoxIcon.Question)
    If intresult = Windows.Forms.DialogResult.No Then
        MessageBox.Show("No seat confirmed")
        Exit Sub
    End If

    Dim btn As Button = Controls("btn" & seatNumber)
    btn.Visible = False
    MessageBox.Show($"Seat {seatNumber} is confirmed", "confirmation")
End Sub

我不太确定您在Form1_Load中要做什么，因为Select Case都不会被击中。无论如何，可以将处理程序附加到按钮的Click事件，如下所示：

For Each ctrl As Control In Controls
    If Not TypeOf ctrl Is Button Then Continue
    If ctrl Is btnClick Then Continue
    AddHandler DirectCast(ctrl, Button).Click, ClickHandler
Next

通过这种方式，我们可以讨论使用ADO.NET在您的程序中对Access数据库进行读写。

---

连接和Execute*方法

在最低级别上，使用连接字符串：

Dim connectionString = 
    "Provider=Microsoft.Jet.OLEDB.4.0;" & 
    "Data Source=" & pathToDatabase

使用OleDbConnection连接到数据库：

Using connection AS New OleDbConnection(connectionString)
    connection.Open

    ' do stuff here

End Using

在打开连接的情况下，您可以使用OleDbCommand执行命令。您可以将命令与ExecuteNonQuery方法一起使用来执行更新查询：

Dim cmdDeleteAll As New OleDbCommand("DELETE * FROM Persons", connection)
cmdDeleteAll.ExecuteNonQuery

或与ExecuteScalar方法一起返回单个结果：

Dim cmdCount As New OleDbCommand("SELECT COUNT(*) FROM Persons", connection)
Dim count As Integer? = cmdCount.ExecuteScalar

或使用ExecuteReader方法返回OleDbDataReader，以对一组结果进行一次迭代-仅向前。

Using cmd As New OleDbCommand("SELECT * FROM Persons", connection),
        rdr = cmd.ExecuteReader
    Do While rdr.Read
        MessageBox.Show($"{rdr["FirstName"]} {rdr["LastName"]}")
    Loop
End Using

---

适配器和DataSet

OleDbDataReader可以从一个结果集中访问一个记录。如果要从多个结果集中加载数据，或者需要将所有数据保留在内存中，则可以使用OleDbDataAdapter从DataSet对象将数据加载到OleDbConnection中：

Dim ds = new DataSet();
Using connection As New OleDbConnection(connectionString)
    Dim sql = "SELECT * FROM Persons"
    Dim adapter = new OleDbDataAdapter(sql, connection)
    adapter.Fill(ds, "Persons")
End Using

由于DataSet可以包含多组数据，因此存在用于处理DataSets及其DataTables的对象层次结构：

（ Source: ADO.NET Architecture ）

---

针对DataReader的LINQ

您还可以在数据读取器上使用LINQ和LINQ方法，以从单个结果集中检索一组对象：

Dim persons As List(Of Person)
Using reader = cmd.ExecuteReader()
    persons = reader.Cast<DbDataRecord>()
        .Select(Function(row) New Person With {
            .LastName = row["LastName"])
            .FirstName = row["FirstName"]
        }).ToList
End Using