如何使用 Visual Basic 更新/修改 Access 數據庫中的現有行

Question

我在使用 VB 更新 Access 數據庫中的現有行時遇到困難。 我希望能夠對訪問表中已填充的現有行中的字段進行更改。

我的代碼與在表格底部而不是上面添加新記錄有關。

Public Class Form1
    Dim objConnection As New OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0; Data Source = StudentDatabase.accdb")
    Dim objStudentDA As New OleDb.OleDbDataAdapter("Select * FROM Student", objConnection)
    Dim objStudentCB As New OleDb.OleDbCommandBuilder(objStudentDA)
    Dim objDs As New DataSet()

 Private Sub btnUpdate_Click(sender As Object, e As EventArgs) Handles btnUpdate.Click

        If txtStudentNum.Text <> "" And txtSurname.Text <> "" And txtAttendance.Text <> "" And txtCA1.Text <> "" And txtCA2.Text <> "" And txtFinalExamResult.Text <> "" Then


            Dim objRow3 = objDs.Tables("Student").Rows.Find(txtUpdateStudentID.Text.ToString)

            'Editing each field value based on textboxes

            objRow3.Item("FName") = txtUpdateFName.Text
            objRow3.Item("SName") = txtUpdateSName.Text
            objRow3.Item("Attendance") = txtUpdateAttendance.Text
            objRow3.Item("CA1") = txtUpdateCA1.Text
            objRow3.Item("CA2") = txtUpdateCA2.Text
            objRow3.Item("FinalExam") = txtUpdateFinalExam.Text
            objRow3.Item("OverallResult") = txtUpdateOverallGrade.Text


**'ERROR HERE STATING THIS ROW ALREADY BELONGS TO A TABLE**

            objDs.Tables("Student").Rows.Add(objRow3)
            objStudentDA.Update(objDs, "Student")
            MsgBox("Record has been added to the IS2215 Database!")
            Retrieve()
        Else
            MsgBox("Error: You must not leave any fields blank!")
        End If
    End Sub

Public Sub Retrieve()

        objDs.Clear()
        objStudentDA.FillSchema(objDs, SchemaType.Source, "Student")
        objStudentDA.Fill(objDs, "Student")
        cmbStudentFind.Items.Clear()
        Dim i As Integer, strCurrentID As String
        For i = 1 To objDs.Tables("Student").Rows.Count
            strCurrentID = objDs.Tables("Student").Rows(i - 1).Item("ID")
            cmbStudentFind.Items.Add(strCurrentID)
            cmbUpdateStudentID.Items.Add(strCurrentID)
        Next
        cmbStudentFind.SelectedIndex = 0
        cmbUpdateStudentID.SelectedIndex = 0

        FillUpdateDetails()


    End Sub

Public Sub FillUpdateDetails()
        Dim objRow2 As DataRow
        objRow2 = objDs.Tables("Student").Rows.Find(cmbUpdateStudentID.SelectedItem.ToString)
        txtUpdateStudentID.Text = objRow2.Item("ID")
        txtUpdateFName.Text = objRow2.Item("FName")
        txtUpdateSName.Text = objRow2.Item("SName")
        txtUpdateAttendance.Text = objRow2.Item("Attendance")
        txtUpdateCA1.Text = objRow2.Item("CA1")
        txtUpdateCA2.Text = objRow2.Item("CA2")
        txtUpdateFinalExam.Text = objRow2.Item("FinalExam")
        txtUpdateOverallGrade.Text = objRow2.Item("OverallResult")


    End Sub

End Class

Answer 1

您需要對數據庫執行 CRUD。 嘗試對 Access 執行這些操作時會遇到很多問題，因為在訪問表時它往往會鎖定表。

我建議您構建一個 CRUD 框架，以便根據需要將插入、更新和/或刪除操作“機槍”到 Access 中。

除此之外，在嘗試讓它發揮作用的過程中，你會掉很多頭發。

Answer 2

對於插入，您可以堅持使用當前的 TextBox 設置。 為了進行更新，我認為 DataGridView 會是一個更好的方法。

像這樣的事情應該適合你。

Imports System.Data.OleDb
Public Class Form1
    Dim connetionString As String
    Dim connection As OleDbConnection
    Dim oledbAdapter As OleDbDataAdapter
    Dim oledbCmdBuilder As OleDbCommandBuilder
    Dim ds As New DataSet
    Dim changes As DataSet
    Dim i As Integer
    Dim sql As String

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        connetionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Your mdb filename;"
        connection = New OleDbConnection(connetionString)
        Sql = "select * from tblUsers"
        Try
            connection.Open()
            oledbAdapter = New OleDbDataAdapter(Sql, connection)
            oledbAdapter.Fill(ds)
            DataGridView1.Data Source= ds.Tables(0)
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Try
            oledbCmdBuilder = New OleDbCommandBuilder(oledbAdapter)
            changes = ds.GetChanges()
            If changes IsNot Nothing Then
                oledbAdapter.Update(ds.Tables(0))
            End If
            ds.AcceptChanges()
            MsgBox("Save changes")
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub
End Class

或者，您可以堅持使用 TextBox 概念，並像這樣稍微更改您的設置。

str = "Journals SET JournalTitle=?, JournalText=? WHERE JournalDate=?"
cmd = New OleDbCommand(str, myConnection) 
cmd.Parameters.AddWithValue("@jounalTitle", MyJournalTitle )
cmd.Parameters.AddWithValue("@journalText", MyJournalText)
cmd.Parameters.AddWithValue("@journalDate", DatePicked)
cmd.ExecuteNonQuery()

這種方法比你現在的方法安全得多。 這里有更多細節。

如何更新 MS Access 數據庫 (vb.net)