不应该抛出的异常

Question

    private async Task<long> InsertCustomerRecord(CreateCustomerModel model)
    {

        Int64 phoneNumber = 0;
        var isParsed = Int64.TryParse(model.PhoneNumber, out phoneNumber);
        if (!isParsed)
            phoneNumber = 0;
        var USPSAddressValidatedId = (int)model.USPSAddressValidated;
        try
        {
            IDataParameter[] parameters = new IDataParameter[]
            {
            new SqlParameter("@FirstName", model.FirstName.ToUpper()),
            new SqlParameter("@LastName", model.LastName.ToUpper()),
            //new SqlParameter("@MiddleInitial", model.MiddleInitial),
            new SqlParameter("@AddressLine1",model.AddressLine1.ToUpper() ?? ""),
            new SqlParameter("@AddressLine2",model.AddressLine2.ToUpper() ?? ""),
            new SqlParameter("@City",model.City.ToUpper()),
            new SqlParameter("@State",model.State.ToUpper()),
            new SqlParameter("@CountyCode",model.CountyCode.ToUpper()),
            new SqlParameter("@ZipCode",model.ZipCode),
            new SqlParameter("@DateOfBirth",model.DateOfBirth.ToShortDateString()),
            new SqlParameter("@Phone",phoneNumber),
            new SqlParameter("@Email",model.EmailAddress.ToUpper()??""),
            new SqlParameter("@PersonalRepresentative",model.CustomerClass.ToUpper()),
            new SqlParameter("@ExpiryDate", model.ExpirationDate),
            new SqlParameter("@CustomerClass", model.Customer_Class),
            new SqlParameter("@USPSAddressValidated",USPSAddressValidatedId ),
            new SqlParameter("@ImportFromLegacySystem", model.ImportFromLegacySystem)
            };
        
            return await InsertUpdateProcedure("RF_InsertCustomerCard", parameters);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
            return 0;
        }
    }

抛出的异常是

{"Object reference not set to an instance of an object."}
    Data: {System.Collections.ListDictionaryInternal}

Answer 1

如果您怀疑某些内容可能为空：

model.EmailAddress
      ^^^^^^^^^^^^
   this might be null

您需要对其使用空传播运算符：

model.EmailAddress?.ToUpper() ?? ""
                  ^^

这意味着如果它是 null，那么操作链的评估将在 .EmailAddress returns null 的点停止，并且子-表达式 (model.EmailAddress?.ToUpper()) 将解析为 null。然后它将被空合并运算符 ?? 拾取并变成您放在运算符右侧的任何内容。如果它是一个常量，比如 "" 那么整个表达式保证不为 null

您可以在属性和方法 return 值上多次使用这些运算符：

thing.Prop?.Method() ?? thing.OtherProp?.OtherMethod()?.AnotherProp ?? "Constant"

如果集合可能为空，还有一个空容忍索引器：

//in case the collection is null, or the thing at index 0 is null, or its Property is null...
thing.Collection?[0]?.Property?.Something() ...
                ^^

不应该抛出的异常

Exception thrown when it shouldn't be

c#

exception

sqlparameter