Question

我无法使用VB更新Access数据库中的现有行。我希望能够对访问表中已填充的现有行中的字段进行更改。

我的代码涉及在表格底部而不是上面添加新记录。

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

您需要对数据库执行CRUD。尝试对Access执行这些操作时会遇到很多问题，因为在访问Table时它往往会锁定表。

我建议您根据需要构建一个CRUD框架，以便将“插入，更新和/或删除”操作“机枪”插入到Access中。

除此之外，在尝试使其发挥作用的过程中，你会失去很多头发。

Answer 2

要制作插页，您可以坚持使用当前的TextBox设置。为了进行更新，我认为DataGridView是一种更好的方法。

这样的事情对你有用。

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，您可以坚持使用TextBox概念，并稍微更改您的设置。

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()

这种方法比现在的方式更安全。这里有更多细节。

How to update MS Access Database (vb.net)

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2 个答案: