สอบถามปัญหาคำสั่ง SQL 2008 save ข้อมูลให้ลงฐานโดยการกำหนด text box ครับ

Imports System.Data
Imports System.Data.SqlClient
Public Class Form1
    Dim Conn As SqlConnection = New SqlConnection
    Dim da As SqlDataAdapter
    Dim add_state As Boolean = False
    Dim dt As New DataTable
    ' Dim db As New DataTable
    Dim land As SqlCommand
    Private bin As New BindingSource

    Dim currRecPos As Integer
    Dim addNewMode As Boolean
    Dim ds As DataSet = New DataSet
    Dim IsFind As Boolean = False



    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click




 Dim strConn As String
        strConn = "Data Source=.\SQLEXPRESS;Initial Catalog=SSPEGIS4;Integrated Security=True"



        Dim sqlupdate As String

        Dim sqladd As String

        sqlupdate = "update land"

        sqlupdate &= " set PARCEL_CODE = '" & txtPARCEL_CODE.Text & "',"
        sqlupdate &= " TAMBON_TH= '" & txtTAMBON_TH.Text & "',"
        sqlupdate &= " DISTRICT_TH= " & Val(txtDISTRICT_TH.Text) & ","
        

        sqladd = "insert into land (PARCEL_CODE,TAMBON_TH,DISTRICT_TH)"

        sqladd &= " values ('" & txtPARCEL_CODE.Text & "',"
        sqladd &= " '" & txtTAMBON_TH.Text & "',"
        sqladd &= "'" & txtDISTRICT_TH.Text & "',"



        Try
            With Conn
                If .State = ConnectionState.Open Then .Close()
                .ConnectionString = strConn
                .Open()
            End With
            land = New SqlCommand
            With land
                .CommandType = CommandType.Text
                If add_state = True Then
                    .CommandText = sqladd
                Else
                    .CommandText = sqlupdate
                End If

                .Connection = Conn
                .ExecuteNonQuery()
            End With
        Catch ErrorToEdit As Exception
            MessageBox.Show(ErrorToEdit.Message & sqladd, "ข้อผิดพลาด", MessageBoxButtons.OK, MessageBoxIcon.Error)
            Exit Sub
        End Try

        add_state = False
        MessageBox.Show("บันทึกข้อมูลเสร็จแล้ว ", "แจ้งให้ทราบ", MessageBoxButtons.OK, MessageBoxIcon.Information)


    End Sub


Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
        addNewMode = True
        currRecPos = bin.Position
        bin.AddNew()

    End Sub

End Class