ผมมีปัญหาเกี่ยวกับ Update กับ Delete ครับ รบกวนท่านผู้รู้ทีนะครับ

Public Class AddChemForm

    Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        Me.Close()
    End Sub

    Private Sub AddChemForm_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Call GetData()
    End Sub
    Sub GetData()
        strSql = "Select Chemical.ChemId AS รหัสสารเคมี, Chemical.ChemName AS ชื่อสารเคมี, " & _
                 "Chemical.ChemUnit AS หน่วยนับ, Chemical.Chemtotal AS จำนวนคงคลัง From Chemical"

        DA.SelectCommand.CommandText = strSql
        DA.Fill(DS, "Getchem")
        DS.Tables("Getchem").Clear()
        DA.Fill(DS, "Getchem")

        DataGridView1.DataSource = DS.Tables("Getchem")
        DataGridView1.ReadOnly = True
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        strSql = "Insert Into Chemical (ChemId, ChemName, ChemUnit, Chemtotal) Values ('" & _
                TextBox1.Text & "','" & TextBox2.Text & "','" & _
                TextBox3.Text & "','" & NumericUpDown1.Text & "')"
        Try
            With Comm
                .CommandText = strSql
                .CommandType = CommandType.Text
                .Connection = Conn
                .ExecuteNonQuery()
            End With

            Call GetData()
            MessageBox.Show("เพิ่มข้อมูลสำเร็จ", "สำเร็จ", MessageBoxButtons.OK, MessageBoxIcon.Information)
        Catch ex As Exception
            MessageBox.Show("มีสารเคมีชนิดนี้อยู่แล้วในฐานข้อมูล", "พบข้อผิดพลาด", MessageBoxButtons.OK, MessageBoxIcon.Warning) ' & vbCrLf & Err.Description
        End Try
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        strSql = "Update Chemical set ChemId = '" & TextBox1.Text & "', ChemName = '" & _
              TextBox2.Text & "', ChemUnit = '" & TextBox3.Text & ", Chemtotal = '" & _
              NumericUpDown1.Text & "'"

        Try
            With Comm
                .CommandText = strSql
                .CommandType = CommandType.Text
                .Connection = Conn
                .ExecuteNonQuery()
            End With


            MessageBox.Show("แก้ไขข้อมูลเสร็จสิ้น", "สำเร็จ", MessageBoxButtons.OK, MessageBoxIcon.Information)
        Catch ex As Exception
            MessageBox.Show("การแก้ไขข้อมูลผิดพลาด", "", MessageBoxButtons.OK, MessageBoxIcon.Warning) ' & vbCrLf & Err.Description
        End Try
        Call GetData()
    End Sub

    Private Sub DataGridView1_CellClick(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellClick
        TextBox1.Text = DataGridView1.Rows(e.RowIndex).Cells(0).Value
        TextBox2.Text = DataGridView1.Rows(e.RowIndex).Cells(1).Value
        TextBox3.Text = DataGridView1.Rows(e.RowIndex).Cells(2).Value
        NumericUpDown1.Text = DataGridView1.Rows(e.RowIndex).Cells(3).Value
        Button1.Enabled = False
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        strSql = "Delete * From Chemical where ChemId = '" & TextBox1.Text & "'"

        Try
            With Comm
                .CommandText = strSql
                .CommandType = CommandType.Text
                .Connection = Conn
                .ExecuteNonQuery()
            End With


            MessageBox.Show("ลบข้อมูลเสร็จสิ้น", "สำเร็จ", MessageBoxButtons.OK, MessageBoxIcon.Information)
        Catch ex As Exception
            MessageBox.Show("การลบข้อมูลผิดพลาด", "", MessageBoxButtons.OK, MessageBoxIcon.Warning) ' & vbCrLf & Err.Description
        End Try
        Call GetData()
    End Sub

    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        TextBox1.Text = ""
        TextBox2.Text = ""
        TextBox3.Text = ""
        NumericUpDown1.Text = ""
        Button1.Enabled = True
    End Sub

End Class