รบกวนช่วยแก้ปัญหาให้หน่อยครับ เพิ่มข้อมูลไม่ได้ vb.net

cboDepartName.Text  --> cboDepartName.SelectedValue

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration

Public Class frmAssign12
    Dim sqlConn As SqlConnection
    Dim sqlDa As SqlDataAdapter
    Dim sqlCom As SqlCommand
    Dim sqlDr As SqlDataReader
    Dim daSet As DataSet
    Dim sqlTs As SqlTransaction
    Dim strCon As String = ConfigurationManager.ConnectionStrings("VisualProgQ1.My.MySettings.daStudent").ConnectionString
    Dim strSql As String
    Dim actStatus As String

Dim _id As String

    Private Sub frmAssign12_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        sqlConn = New SqlConnection
        sqlConn.ConnectionString = strCon
        sqlConn.Open()

        strSql = "select stdId, stdName, stdLname, address, sex, gpa, tbDepartment.departName from tbStudent, tbDepartment where tbStudent.departID=tbDepartment.departID"

        sqlDa = New SqlDataAdapter(strSql, strCon)
        daSet = New DataSet
        daSet.Clear()
        sqlDa.Fill(daSet, "Show")
        dgvStudent.DataSource = daSet.Tables("Show")
    End Sub

    Private Sub dgvStudent_CellEnter(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles dgvStudent.CellEnter
        Dim Row As Integer
        Row = dgvStudent.CurrentCell.RowIndex
        txtStdId.Text = dgvStudent.Item(0, Row).Value
        txtStdName.Text = dgvStudent.Item(1, Row).Value
        txtStdLname.Text = dgvStudent.Item(2, Row).Value
        txtAddress.Text = dgvStudent.Item(3, Row).Value
        If dgvStudent.Item(4, Row).Value = "ชาย" Then
            radMale.Checked = True
        Else
            radFemale.Checked = True
        End If
        txtGpa.Text = dgvStudent.Item(5, Row).Value
        cboDepartName.SelectedIndex = cboDepartName.Items.Add(dgvStudent.Item(6, Row).Value)
    End Sub

    Private Sub showDep()
        If sqlConn.State = ConnectionState.Closed Then
            sqlConn.Open()
        End If

        strSql = "Select departName from tbDepartment"

        sqlCom = New SqlCommand(strSql, sqlConn)
        sqlDr = sqlCom.ExecuteReader
        If sqlDr.HasRows Then
            While sqlDr.Read
                cboDepartName.Items.Add(sqlDr(0))
            End While
            cboDepartName.SelectedIndex = cboDepartName.Items.Count = 0
            sqlDr.Close()
        End If
    End Sub

    Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
        actStatus = "insert"
        dgvStudent.Enabled = False
        panStudent.Enabled = True
        btnAdd.Enabled = False
        btnEdit.Enabled = False
        btnDel.Enabled = False
        btnSave.Enabled = True
        btnCance.Enabled = True
        txtStdId.Clear()
        txtStdName.Clear()
        txtStdLname.Clear()
        txtAddress.Clear()
        txtGpa.Clear()
        radMale.Checked = True
        txtStdId.Focus()
        cboDepartName.Items.Clear()

        If sqlConn.State = ConnectionState.Closed Then
            sqlConn.Open()
        End If

        strSql = "Select departName from tbDepartment"

        sqlCom = New SqlCommand(strSql, sqlConn)
        sqlDr = sqlCom.ExecuteReader
        If sqlDr.HasRows Then
            While sqlDr.Read
                cboDepartName.Items.Add(sqlDr(0))
            End While
            cboDepartName.SelectedIndex = cboDepartName.Items.Count = 0
            sqlDr.Close()
        End If
    End Sub

    Private Sub btnEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEdit.Click
        actStatus = "edit"
        dgvStudent.Enabled = False
        panStudent.Enabled = True
        btnAdd.Enabled = False
        btnEdit.Enabled = False
        btnDel.Enabled = False
        btnSave.Enabled = True
        btnCance.Enabled = True
        cboDepartName.Items.Clear()


    End Sub

    Private Sub btnDel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDel.Click
        
    End Sub

    Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click
        Dim sex As String
        Dim intResult As Integer
        If radMale.Checked = True Then
            sex = "ชาย"
        Else
            sex = "หญิง"
        End If
        If actStatus = "insert" Then
            strSql = "insert into tbStudent values('" & txtStdId.Text & "','" & txtStdName.Text & "','" & txtStdLname.Text & "','" & txtAddress.Text & "','" & sex & "','" & txtGpa.Text & "','" & cboDepartName.Text & "')"
        End If
        sqlCom = New SqlCommand
        sqlCom.CommandType = CommandType.Text
        sqlCom.CommandTimeout = 15
        sqlCom.CommandText = strSql
        sqlCom.Connection = sqlConn
        sqlTs = sqlConn.BeginTransaction
        sqlCom.Transaction = sqlTs
        Try
            intResult = sqlCom.ExecuteNonQuery
            MessageBox.Show("บันทึกข้อมูลเรียบร้อย...")
            sqlTs.Commit()
            Call frmAssign12_Load(sender, e)
        Catch
            MessageBox.Show("เกิดข้อผิดพลาด ไม่สามารถบันทึกได้...")
            sqlTs.Rollback()
        End Try
        Call btnCance_Click(sender, e)
    End Sub

    Private Sub btnCance_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCance.Click
        dgvStudent.Enabled = True
        panStudent.Enabled = False
        btnAdd.Enabled = True
        btnEdit.Enabled = True
        btnDel.Enabled = True
        btnSave.Enabled = False
        btnCance.Enabled = False
        cboDepartName.Items.Clear()
        Call frmAssign12_Load(sender, e)
    End Sub

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

Private Sub cboDepartName_TextChanged(ByVal sender As System.Object, Byval e As System.EventArgs) Handles cboDepartName.TextChanged
  sqlConn = New SqlConnection
        sqlConn.ConnectionString = strCon
        sqlConn.Open()

        strSql = "select departID From tbDepartment WHERE departName  = @departName"
        sqlCom = New SqlCommand
        sqlCom.CommandType = CommandType.Text
        sqlCom.CommandTimeout = 15
        sqlCom.CommandText = strSql
        sqlCom.Connection = sqlConn
        sqlCom.Parameter.Addwithvalue("@departName", cboDepartName.text)
       Dim sqldataReader = new SQLdatareader()
     sqldataReader = sqlCom.executereader()
      sqldatareader.read()
if sqldatareader.hasrow then
_id = sqldatareader("departID ")
end if
      

End Sub

End Class