SampleApp.MainForm.MenuFileOpen_Click C# (CSharp) Method

        private void MenuFileOpen_Click(object sender, EventArgs e)
        {
            if (openFileDialog.ShowDialog(this) == DialogResult.OK)
            {
                string filename = openFileDialog.FileName;
                string extension = Path.GetExtension(filename);
                if (extension == ".xls" || extension == ".xlsx")
                {
                    ExcelReader db = new ExcelReader(filename, true, false);
                    TableSelectDialog t = new TableSelectDialog(db.GetWorksheetList());

                    if (t.ShowDialog(this) == DialogResult.OK)
                    {
                        DataTable tableSource = db.GetWorksheet(t.Selection);

                        double[,] sourceMatrix = tableSource.ToMatrix(out sourceColumns);

                        // Detect the kind of problem loaded.
                        if (sourceMatrix.GetLength(1) == 2)
                        {
                            MessageBox.Show("Missing class column.");
                        }
                        else
                        {
                            this.dgvLearningSource.DataSource = tableSource;
                            this.dgvTestingSource.DataSource = tableSource.Copy();

                            graphInput.DataSource = sourceMatrix;

                            // enable "Start" button
                            startButton.Enabled = true;
                        }
                    }
                }
            }
        }