สอบถามเรื่อง violation of primary key constraint ในคำสั่ง INSERT & UPDATE

  If txtidtype.Text = "" Or txttypename.Text = "" Then
            MessageBox.Show("กรุณากรอกข้อมูลให้ครบถ้วนด้วยครับ", "คำเตือน", MessageBoxButtons.OK, MessageBoxIcon.Warning)
        Else
            Call InsertData()
            Dim ssql As String

            ssql = "UPDATE DrugsType SET DrugstypeName='" & txttypename.Text & "' WHERE DrugstypeID='" & txtidtype.Text & "'"

            Try
                dbOpen()

                Com = New SqlCommand(ssql, Conn)

                If Com.ExecuteNonQuery() = 1 Then
                    MessageBox.Show("Edit complete.", "Status", MessageBoxButtons.OK, MessageBoxIcon.Information)
                End If
                dgvdrugtype.DataSource = GetData()
            Catch ex As Exception
                MsgBox(ex.Message)
            End Try
            Call ClearData()
        End If

  If MessageBox.Show("คุณต้องการเพิ่มข้อมูลลูกค้าใช่หรืไม่", "คำยืนยัน", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.Yes Then

            Try
                tr = Conn.BeginTransaction
                Com.Parameters.Clear()
                Dim sql As String = ""
                dbOpen()
                sql = " Insert Into DrugsType(DrugstypeID, DrugstypeName) values(@1,@2)"
                Com = New SqlCommand(sql, Conn)
                With Com.Parameters
                    .Add(New SqlParameter("@1", txtidtype.Text))
                    .Add(New SqlParameter("@2", txttypename.Text))


                End With

                Com.ExecuteNonQuery()
                Com.Parameters.Clear()
                dgvdrugtype.DataSource = GetData()
            Catch ex As Exception
                tr.Rollback()
                MsgBox(ex.Message)
            End Try

        End If