更新SQL失败

Question

这是我的代码

 Private Sub btn_fast200_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn_fast200.Click
        Using _conn As New SqlConnection("Data Source=HOME-PC; Initial Catalog=csbanking; Integrated Security= true")
            Using _comm As New SqlCommand()
                With _comm
                    .Connection = _conn
                    .CommandText = "UPDATE USERLOGIN SET USER_BALANCE = @balance + USER_BALANCE WHERE USER_LOGIN=@id"
                    .CommandType = CommandType.Text
                    .Parameters.AddWithValue("@balance", -200)
                    .Parameters.AddWithValue("@id", Login.txt_id.Text)

                End With
                Try
                    _conn.Open()
                    _comm.ExecuteNonQuery()
                Catch ex As SqlException
                    MsgBox(ex.Message.ToString())
                End Try
            End Using
        End Using
        MessageBox.Show("Transaction Success")
        _1stpage.Show()
        Login.txt_id.Text = ""
        Security.msktxt_pin.Text = ""
        Me.Hide()

    End Sub

添加后无法更新余额（“WHERE USER_LOGIN = @ id”）