目的是为了处理combox1选择值后自计算另一textbox1的值,但此时计算逻辑中的另一combox2的值为NULL故报错,此时只能
使用try catch处理错误
private void getCoefficiet() { try { txt_coefficient.Text = new CoefficientService().coefficients(). Where(q => q.CustomerID.ToString() == cmb_custName.SelectedValue.ToString() & q.ScrapID.ToString() == cmb_scrapName.SelectedValue.ToString()). Select(s => s.Data).ToList().FirstOrDefault().ToString(); } //当cmb_scrapNaem的值为NULL时 catch (Exception) { txt_coefficient.Text = ""; } }