Question

这部分代码是让讲师发布咨询时间表，不幸的是，在Can anybody help me to solve this error "NullReferenceException was unhandled"?完成提问后，我在标题中显示了另一个错误，并且该错误可能已得到解决。现在，我的问题是当我点击发布按钮时，就像将所有标签（表格中显示的颜色为石灰）保存到访问文件中，并且那些标签已经声明为（lime = available，red = unavailable））。

This is the form

错误发生在Dim f As Integer = cmd.ExecuteNonQuery（）

    Public Class ConsultationSchedule

Private Sub publishbutton_Click(sender As Object, e As EventArgs) Handles publishbutton.Click
    Dim label As String = "Label"

    Dim time1 As String = vbNull
    Dim time2 As String = vbNull
    Dim time3 As String = vbNull
    Dim time4 As String = vbNull
    Dim time5 As String = vbNull

    Dim day1 As String = vbNull
    Dim day2 As String = vbNull
    Dim day3 As String = vbNull
    Dim day4 As String = vbNull
    Dim day5 As String = vbNull

    Dim available1 As String = vbNull
    Dim available2 As String = vbNull
    Dim available3 As String = vbNull
    Dim available4 As String = vbNull
    Dim available5 As String = vbNull

    For i = 11 To 15
        time1 = Label7.Text

        For k = 16 To 20
            time2 = Label8.Text

            For t = 21 To 25
                time3 = Label9.Text

                For u = 26 To 30
                    time4 = Label10.Text

                    For bg = 33 To 37
                        time5 = Label32.Text

                    Next
                Next
            Next
        Next
    Next

    For i = 11 To 37
        If (i = 11) Then
            day1 = Label2.Text
            If Not Me.Controls(label & i.ToString) Is Nothing Then
                If (Me.Controls(label & i.ToString).BackColor = Color.Lime) Then
                    available1 = "Available"
                Else
                    available1 = "Unavailable"
                End If
            End If

        ElseIf (i = 16) Then
            day1 = Label2.Text
            If Not Me.Controls(label & i.ToString) Is Nothing Then
                If (Me.Controls(label & i.ToString).BackColor = Color.Lime) Then
                    available2 = "Available"
                Else
                    available2 = "Unavailable"
                End If
            End If

        ElseIf (i = 21) Then
            day1 = Label2.Text
            If Not Me.Controls(label & i.ToString) Is Nothing Then
                If (Me.Controls(label & i.ToString).BackColor = Color.Lime) Then
                    available3 = "Available"
                Else
                    available3 = "Unavailable"
                End If
            End If

        ElseIf (i = 26) Then
            day1 = Label2.Text
            If Not Me.Controls(label & i.ToString) Is Nothing Then
                If (Me.Controls(label & i.ToString).BackColor = Color.Lime) Then
                    available4 = "Available"
                Else
                    available4 = "Unavailable"
                End If
            End If

        ElseIf (i = 33) Then
            day1 = Label2.Text
            If Not Me.Controls(label & i.ToString) Is Nothing Then
                If (Me.Controls(label & i.ToString).BackColor = Color.Lime) Then
                    available5 = "Available"
                Else
                    available5 = "Unavailable"
                End If
            End If
        End If
    Next
    For ht = 11 To 37
        If (ht = 11) Then
            day1 = Label2.Text
        ElseIf (ht = 16) Then
            day1 = Label2.Text
        ElseIf (ht = 21) Then
            day1 = Label2.Text
        ElseIf (ht = 26) Then
            day1 = Label2.Text
        ElseIf (ht = 33) Then
            day1 = Label2.Text
        End If
    Next
    For k = 11 To 37
        If (k = 12) Then
            day2 = Label3.Text
        ElseIf (k = 17) Then
            day2 = Label3.Text
        ElseIf (k = 22) Then
            day2 = Label3.Text
        ElseIf (k = 27) Then
            day2 = Label3.Text
        ElseIf (k = 34) Then
            day2 = Label3.Text
        End If
    Next
    For t = 11 To 37
        If (t = 13) Then
            day3 = Label4.Text
        ElseIf (t = 18) Then
            day3 = Label4.Text
        ElseIf (t = 23) Then
            day3 = Label4.Text
        ElseIf (t = 28) Then
            day3 = Label4.Text
        ElseIf (t = 35) Then
            day3 = Label4.Text
        End If
    Next
    For u = 11 To 37
        If (u = 14) Then
            day4 = Label5.Text
        ElseIf (u = 19) Then
            day4 = Label5.Text
        ElseIf (u = 24) Then
            day4 = Label5.Text
        ElseIf (u = 29) Then
            day4 = Label5.Text
        ElseIf (u = 36) Then
            day4 = Label5.Text
        End If
    Next
    For y = 11 To 37
        If (y = 15) Then
            day5 = Label6.Text
        ElseIf (y = 20) Then
            day5 = Label6.Text
        ElseIf (y = 25) Then
            day5 = Label6.Text
        ElseIf (y = 30) Then
            day5 = Label6.Text
        ElseIf (y = 37) Then
            day5 = Label6.Text
        End If
    Next

    Dim sql As String
    Dim sql2 As String
    Dim sql3 As String
    Dim sql4 As String
    Dim sql5 As String

    Dim cmd As OleDbCommand
    Dim cmd2 As OleDbCommand
    Dim cmd3 As OleDbCommand
    Dim cmd4 As OleDbCommand
    Dim cmd5 As OleDbCommand

    Dim conn = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=scheduledatabase.accdb;Persist Security Info=False;")
    sql = "INSERT INTO consultationschedule([Time], weekDay, Available)VALUES(@time1,@day1,@available1)"
    sql2 = "INSERT INTO consultationschedule([Time], weekDay, Available)VALUES(@time2,@day2,@available2)"
    sql3 = "INSERT INTO consultationschedule([Time], weekDay, Available)VALUES(@time3,@day3,@available3)"
    sql4 = "INSERT INTO consultationschedule([Time], weekDay, Available)VALUES(@time4,@day4,@available4)"
    sql5 = "INSERT INTO consultationschedule([Time], weekDay, Available)VALUES(@time5,@day5,@available5)"

    Using (conn)
        conn.Open()
        cmd = New OleDbCommand(sql, conn)
        cmd.Parameters.Add(New OleDbParameter("@Time", time1))
        cmd.Parameters.Add(New OleDbParameter("@weekDay", day1))
        cmd.Parameters.Add(New OleDbParameter("@Available", available1))
        cmd2 = New OleDbCommand(sql2, conn)
        cmd2.Parameters.Add(New OleDbParameter("@Time", time2))
        cmd2.Parameters.Add(New OleDbParameter("@weekDay", day2))
        cmd2.Parameters.Add(New OleDbParameter("@Available", available2))
        cmd3 = New OleDbCommand(sql3, conn)
        cmd3.Parameters.Add(New OleDbParameter("@Time", time3))
        cmd3.Parameters.Add(New OleDbParameter("@weekDay", day3))
        cmd3.Parameters.Add(New OleDbParameter("@Available", available3))
        cmd4 = New OleDbCommand(sql4, conn)
        cmd4.Parameters.Add(New OleDbParameter("@Time", time4))
        cmd4.Parameters.Add(New OleDbParameter("@weekDay", day4))
        cmd4.Parameters.Add(New OleDbParameter("@Available", available4))
        cmd5 = New OleDbCommand(sql5, conn)
        cmd5.Parameters.Add(New OleDbParameter("@Time", time5))
        cmd5.Parameters.Add(New OleDbParameter("@weekDay", day5))
        cmd5.Parameters.Add(New OleDbParameter("@Available", available5))

        Dim f As Integer = cmd.ExecuteNonQuery()
        If (f >= 1) Then
            ToolStrip1.Text += f.ToString & " record added successfully"
        Else
            ToolStrip1.Text += "Unable to add record"
        End If
    End Using
End Sub

Answer 1

我建议你创建一个创建记录的新方法：

 Private Sub AddRecords(ByVal time As String, ByVal day As String, ByVal available As String)

        Dim sql As String
        Dim cmd As OleDbCommand

        Dim conn = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=scheduledatabase.accdb;Persist Security Info=False;")
        sql = "INSERT INTO consultationschedule(Time, weekDay, Available)VALUES(@Time,@weekDay,@Available)"

        Using (conn)
            conn.Open
            cmd = New OleDbCommand(sql, conn)
            cmd.Parameters.AddWithValue("@Time", time)
            cmd.Parameters.AddWithValue("@weekDay", day)
            cmd.Parameters.AddWithValue("@Available", available)
            Dim f As Integer = cmd.ExecuteNonQuery()
            If (f >= 1) Then
                ToolStrip1.Text += f.ToString & " record added successfully"
            Else
                ToolStrip1.Text += "Unable to add record"

            End If
            MessageBox.Show("User Widrawed", "Widrawed", MessageBoxButtons.OK, MessageBoxIcon.Information)
        End Using
    End Sub

之后你可以调用添加记录的方法

AddRecords(time1, day1, available1)
AddRecords(time2, day2, available2)
AddRecords(time3, day3, available3)
AddRecords(time4, day4, available4)
AddRecords(time5, day5, available5)

任何人都可以帮我解决这个错误＆＃34; OleDbException未得到处理＆＃34;？

1 个答案: