是否可以在列數據類型為double的列中插入null值？

Question

     `enter code here`

                private void btnSave_Click(object sender, RoutedEventArgs e)
                            {
                         GRepository<tblDEIPO_Primary> GR = new GRepository<tblDEIPO_Primary>();
                                    tblDEIPO_Primary objDIE = new tblDEIPO_Primary();
                                    if (txtid.Text == "")
                                    {
                                        objDIE.DIEPONo = txtDIEPO.Text;
                                        objDIE.PoDate = dtpDeiPoDate.Text;
                                        objDIE.Vendor = cmbVendor.Text;
                                        objDIE.Remark = txtRemark.Text;
                                        objDIE.TermsAndConditions = txtTermsAndCondition.Text;
                                        objDIE.TaxType = cmbTaxtype.Text;
                                        objDIE.Tax = Convert.ToDouble(txtTax.Text);
                                        objDIE.TaxAmount = Convert.ToDouble(txtTaxAmount.Text);
                                        objDIE.BonusPenalty = s;
                                        if (chkBonus.IsChecked == true)
                                        {
                                            objDIE.BonusPenaltyAmount = Convert.ToDouble(txtBonus.Text);
                                        }
                                        else if (chkPenalty.IsChecked == true)
                                        {
                                            objDIE.BonusPenaltyAmount = Convert.ToDouble(txtPenalty.Text);
                                        }
                                        objDIE.DeiType = cmbDieType.Text;
                                        objDIE.TypeofInjections = cmbTypeOfInjection.Text;
                                        objDIE.Total =Convert.ToDouble( txtTotal.Text);
                                        objDIE.TotalAmount =Convert.ToDouble(txtAmount.Text);
                                        GR.Insert(objDIE);
                                        GR.Save();}

當我單擊btnSave_Click按鈕時，發生時間錯誤，提示“輸入字符串格式不正確。” 在objDIE.Tax = Convert.ToDouble（txtTax.Text）;中 因為該文本框中的insertin值為空白，所以該錯誤Plz幫助的任何解決方案。

                    > Blockquote

Answer 1

所以使用double.TryParse

double taxAmount= 0;
objDIE.TaxAmount = double.TryParse(txtTaxAmount.Text, out taxAmount) ? taxAmount: DbNull.Value;

Answer 2

您可以使用double.TryParse來測試輸入的值是否為double。

您可以替換：

objDIE.TaxAmount = Convert.ToDouble(txtTaxAmount.Text);

通過

double num;
bool res = double.TryParse(txtTax.Text, out num);
if (res)
{
    // String is a double.
    objDIE.TaxAmount = num;
}