private void btnConvertToXls_Click(object sender, EventArgs e) { if (!File.Exists(xlsConvertInputFile.Text)) { MessageBox.Show("Input file not found :(", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); return; } if (string.IsNullOrEmpty(xlsConvertOutputFolder.Text)) { MessageBox.Show("Please select an output folder", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); return; } btnConvertToXls.Enabled = false; Thread t = new Thread(() => { string outputFileName = string.Format("{0}\\{1}.xlsx", xlsConvertOutputFolder.Text, Path.GetFileNameWithoutExtension(xlsConvertInputFile.Text)); m_dataProcessor.ConvertToXls(xlsConvertInputFile.Text, outputFileName); }); t.Start(); }