พี่ๆ ครับ ช่วยดูให้หน่อยครับ มัน Insert ไม่ได้ครับ ไม่รู้ว่าจะแก่ยังไงครับ ชาวยทีครับ

Option Explicit On
Option Strict On
Imports System.IO
Imports System.Data
Imports System.Data.OleDb
Public Class frmAddStudent
    Dim Conn As New OleDbConnection()
    Dim da As OleDbDataAdapter
    Dim ds As New DataSet
    Dim dt As New DataTable
    Dim dv As New DataView
    Dim btnChk, curcode As String
    Dim comStudent As OleDbCommand
    Dim chkFillter As Boolean = False

    Private Sub frmAddStudent_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        With Conn
            If .State = ConnectionState.Open Then .Close()
            .ConnectionString = strConn
            .Open()
        End With
        ShowData()
    End Sub
    Private Sub cmdClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdClose.Click
        Me.Close()
    End Sub

    Private Sub cmdDelete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdDelete.Click
        Dim sqltxt As String = ""
        Dim comtxt As New OleDbCommand
        Dim result As String
        Dim level As String = ""
        If p1.Checked Then
            level = "1"
        ElseIf p2.Checked Then
            level = "2"
        ElseIf p3.Checked Then
            level = "3"
        ElseIf p4.Checked Then
            level = "4"
        ElseIf p5.Checked Then
            level = "5"
        Else
            level = "6"
        End If

        sqltxt = "delete student set code ='"
        sqltxt = sqltxt & txtcode.Text & "',code='"
        sqltxt = sqltxt & txtyear.Text & "',year='"
        sqltxt = sqltxt & txtfullname.Text & "',fullname='"
        sqltxt = sqltxt & level & "',level='"
        sqltxt = sqltxt & " where code='" & curcode & "'"

        result = MessageBox.Show("ต้องการลบข้อมูล", "Warnning", MessageBoxButtons.OKCancel, MessageBoxIcon.Warning).ToString
        If (result = "OK") Then
            With comtxt
                .CommandType = CommandType.Text
                .CommandText = sqltxt
                .Connection = Conn
                .ExecuteNonQuery()
            End With
            btnSwitchOff()
        End If
    End Sub
    Private Sub btnSwitchOn()
        cmdSave.Enabled = True
        cmdCancel.Enabled = True
        cmdClose.Enabled = True
        cmdAdd.Enabled = False
        cmdEdit.Enabled = True
        cmdDelete.Enabled = False
    End Sub
    Private Sub btnSwitchOff()
        cmdSave.Enabled = False
        cmdCancel.Enabled = False
        cmdClose.Enabled = True
        cmdAdd.Enabled = True
        cmdEdit.Enabled = False
        cmdDelete.Enabled = False
    End Sub

    Private Sub cmdedit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdedit.Click
        btnChk = "edit"
        btnSwitchOn()
    End Sub

    Private Sub cmdAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdAdd.Click
        btnSwitchOn()
        btnChk = "add"
        txtcode.Clear()
        txtyear.Clear()
        txtfullname.Clear()
        If txtcode.Text.Trim = "" Then
            txtcode.Focus()
        Else
            p1.Focus()
        End If
    End Sub

    Private Sub cmdCancel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdCancel.Click
        btnSwitchOff()
    End Sub

    Private Sub cmdSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSave.Click
        Dim sqltxt As String = ""
        Dim level As String = ""
        Dim comtxt As New OleDbCommand
        btnSwitchOff()
        If txtcode.Text.Trim <> "" Then
            If p1.Checked Then
                level = "1"
            ElseIf p2.Checked Then
                level = "2"
            ElseIf p3.Checked Then
                level = "3"
            ElseIf p4.Checked Then
                level = "4"
            ElseIf p5.Checked Then
                level = "5"
            Else
                level = "6"
            End If
            If btnChk = "add" Then
                sqltxt = "insert into student(code,year,fullname,level) values('"
                sqltxt = sqltxt & txtcode.Text & "','"
                sqltxt = sqltxt & txtyear.Text & "','"
                sqltxt = sqltxt & txtfullname.Text & "','"
                sqltxt = sqltxt & level & "','"

            ElseIf btnChk = "edit" Then
                sqltxt = "update student set code ='"
                sqltxt = sqltxt & txtcode.Text & "','"
                sqltxt = sqltxt & txtyear.Text & "','"
                sqltxt = sqltxt & txtfullname.Text & "','"
                sqltxt = sqltxt & level & "','"
                sqltxt = sqltxt & " where code = '" & curcode & "'"
            End If
            With comtxt
                .CommandType = CommandType.Text
                .CommandText = sqltxt
                .Connection = Conn
                .ExecuteNonQuery()
            End With
            btnSwitchOff()
        Else
            MessageBox.Show("กรอกข้อมูลไม่ครบ", "WARNING", MessageBoxButtons.OK, MessageBoxIcon.Warning)
            txtcode.Focus()
        End If
    End Sub
    Private Sub ShowData()
        Dim sqlYear As String = "select  * from student"
        da = New OleDbDataAdapter(sqlYear, Conn)
        ds.Clear()
        da.Fill(ds, "student")
        If ds.Tables("student").Rows.Count <> 0 Then
            dv = New DataView(ds.Tables("student"))
            With dgvStudent
                .DataSource = dv
            End With
            DgvFormat()
        End If
    End Sub
    Private Sub DgvFormat()
        With dgvStudent
            .Columns(0).Width = 70
            .Columns(0).HeaderText = "รหัส"
            .Columns(1).Width = 100
            .Columns(1).HeaderText = "เข้าศึกษา"
            .Columns(2).Width = 220
            .Columns(2).HeaderText = "ชื่อ - สกุล"
            .Columns(3).Width = 130
            .Columns(3).HeaderText = "ชั้น"
        End With
    End Sub
    Private Sub dgvStudent_CellClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles dgvStudent.CellContentClick
        Dim level As String = ""
        If e.RowIndex > -1 Then
            With dgvStudent
                txtcode.Text = .Rows.Item(e.RowIndex).Cells(0).Value.ToString()
                txtyear.Text = .Rows.Item(e.RowIndex).Cells(1).Value.ToString()
                txtfullname.Text = .Rows.Item(e.RowIndex).Cells(2).Value.ToString
                level = .Rows.Item(e.RowIndex).Cells(3).Value.ToString()
                If level = "1" Then
                    p1.Checked = True
                ElseIf level = "2" Then
                    p2.Checked = True
                ElseIf level = "3" Then
                    p3.Checked = (True)
                ElseIf level = "4" Then
                    p4.Checked = (True)
                ElseIf level = "5" Then
                    p5.Checked = (True)
                ElseIf level = "6" Then
                    p6.Checked = (True)
                End If
                level = .Rows.Item(e.RowIndex).Cells(3).Value.ToString()
            End With
            cmdDelete.Enabled = True
            cmdedit.Enabled = True
        End If
    End Sub
End Class

Private Sub cmdSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSave.Click
        Dim sqltxt As String = ""
        Dim level As String = ""
        Dim comtxt As New OleDbCommand
        btnSwitchOff()
        If txtcode.Text.Trim <> "" Then
            If p1.Checked Then
                level = "1"
            ElseIf p2.Checked Then
                level = "2"
            ElseIf p3.Checked Then
                level = "3"
            ElseIf p4.Checked Then
                level = "4"
            ElseIf p5.Checked Then
                level = "5"
            Else
                level = "6"
            End If
            If btnChk = "add" Then
                sqltxt = "insert into student(code,year,fullname,level) values('"
                sqltxt = sqltxt & txtcode.Text & "','"
                sqltxt = sqltxt & txtyear.Text & "','"
                sqltxt = sqltxt & txtfullname.Text & "','"
                sqltxt = sqltxt & level & "')"     ' Revise this line

            ElseIf btnChk = "edit" Then
                sqltxt = "update student set code ='"
                sqltxt = sqltxt & txtcode.Text & "','"
                sqltxt = sqltxt & txtyear.Text & "','"
                sqltxt = sqltxt & txtfullname.Text & "','"
                sqltxt = sqltxt & level & "','"
                sqltxt = sqltxt & " where code = '" & curcode & "'"
            End If
            With comtxt
                .CommandType = CommandType.Text
                .CommandText = sqltxt
                .Connection = Conn
                .ExecuteNonQuery()
            End With
            btnSwitchOff()
        Else
            MessageBox.Show("กรอกข้อมูลไม่ครบ", "WARNING", MessageBoxButtons.OK, MessageBoxIcon.Warning)
            txtcode.Focus()
        End If
    End Sub
 

sqltxt = "update student set code ='"
                sqltxt = sqltxt & txtcode.Text & "','"
                sqltxt = sqltxt & txtyear.Text & "','"
                sqltxt = sqltxt & txtfullname.Text & "','"
                sqltxt = sqltxt & level & "','"
                sqltxt = sqltxt & " where code = '" & curcode & "'"

Dim sqltxt As String = ""
        Dim level As String = ""
        Dim comtxt As New OleDbCommand
        btnSwitchOff()
        If txtcode.Text.Trim <> "" Then
            If p1.Checked Then
                level = "ป.1"
            Else
                If p2.Checked Then
                    level = "ป.2"
                Else
                    If p3.Checked Then
                        level = "ป.3"
                    Else
                        If p4.Checked Then
                            level = "ป.4"
                        Else
                            If p5.Checked Then
                                level = "ป.5"
                            Else
                                If p6.Checked Then
                                    level = "ป.6"
                                End If
                            End If
                        End If
                    End If
                End If
            End If
            If btnChk = "add" Then
                sqltxt = "insert into [student]([code],[year],[fullname],[level]) values('"
                sqltxt = sqltxt & txtcode.Text & "','"
                sqltxt = sqltxt & txtyear.Text & "','"
                sqltxt = sqltxt & txtfullname.Text & "','"
                sqltxt = sqltxt & level & "')"
            ElseIf btnChk = "edit" Then
                sqltxt = "UPDATE [student] SET [code] ='" & txtcode.Text & "',"
                sqltxt &= "[year] = '" & txtyear.Text & "',"
                sqltxt &= "[fullname] ='" & txtfullname.Text & "' WHERE ([id] ="
                sqltxt &= CInt(txtid.Text) & ")"
                MessageBox.Show(sqltxt)
            End If
            With comtxt
                .CommandType = CommandType.Text
                .CommandText = sqltxt
                .Connection = Conn
                .ExecuteNonQuery()
            End With
            btnSwitchOff()
        Else
            MessageBox.Show("ไม่ได้กรอกปีที่จัดกิจกรรม", "WARNING", MessageBoxButtons.OK, MessageBoxIcon.Warning)
            txtcode.Focus()
        End If
        ShowData()
    End Sub

    Private Sub ShowData()
        Dim sqlStudent As String = "select  * from student"
        da = New OleDbDataAdapter(sqlStudent, Conn)
        ds.Clear()
        da.Fill(ds, "student")

        If ds.Tables("student").Rows.Count <> 0 Then
            dv = New DataView(ds.Tables("student"))
            With dgvStudent
                .DataSource = dv
            End With
            DgvFormat()
        End If