private void btnImport_Click(object sender, EventArgs e) { if (_SelectedCoverage != null && _SelectedCoverage.LookupTable != null) { OpenFileDialog ofd = new OpenFileDialog(); ofd.Filter = "csv file|*.csv|all files|*.*"; if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK) { _SelectedCoverage.ImportFrom(ofd.FileName); } } else { MessageBox.Show("You should creat lookup table at first", "Import", MessageBoxButtons.OK, MessageBoxIcon.Warning); } }