Question

我正在使用ASP.NET Forms应用程序，为了简单起见，我添加了模型属性[TotalService]＆amp; [PurchasedorReinstatedService]我将来自另一个Model的值存储到此属性中，以便在第一个Model中使用。

然后我尝试引用此Model属性并为其设置ASP Label .Text属性。问题是，我一直得到NullReferenceExceptions，特别是：

An exception of type 'System.NullReferenceException' occurred in PROJECT.dll but was not handled in user code

Additional information: Object reference not set to an instance of an object.

这是我的自定义控件，我收到错误：

using PROJECT.Models.Default;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using PROJECT.Classes;

namespace PROJECT.CustomControls.Default
{
    public partial class YearsOfService : System.Web.UI.UserControl
    {
        public List<Years_Of_Service> yos { get; set; }
        public Years_Of_Service_Data yosd { get; set; }


        protected void Page_Load(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                ApplyData();
            }
        }

        private void ApplyData()
        {
            salaryGridView.DataSource = yos;
            salaryGridView.DataBind();

            if (yosd.YearsOfService.OrderByDescending(y => y.TotalService).FirstOrDefault().ToString() != null)
            {
                creditSalLabel.Text = yosd.YearsOfService.OrderByDescending(y => y.TotalService).FirstOrDefault().ToString();
            }
            else
            {
                creditSalLabel.Text = String.Empty;
            }

            //creditSalLabel.Text = yosd.YearsOfService.OrderByDescending(y => y.TotalService).FirstOrDefault() != null ? yosd.YearsOfService.OrderByDescending(y => y.TotalService).FirstOrDefault().ToString() : String.Empty;

            //purchaseCreditLabel.Text = yosd.YearsOfService.OrderByDescending(y => y.PurchasedorReinstatedService).FirstOrDefault() != null ? yosd.YearsOfService.OrderByDescending(y => y.PurchasedorReinstatedService).FirstOrDefault().ToString() : string.Empty;
        }
    }
}

这是我的Years_Of_Service型号：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace PROJECT.Models.Default
{
    public class Years_Of_Service
    {
        public int Year { get; set; }
        public string FiscalYear
        {
            get
            {
                return Year + "-" + (Year + 1);
            }
        }
        public decimal ServiceCredited { get; set; }
        public decimal Salary { get; set; }
        public string CoveredEmployer { get; set; }

        // New properties added for Label Values
        public string TotalService { get; set; }
        public string PurchasedorReinstatedService { get; set; }
    }
}

Years_Of_Service_Data型号：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace PROJECT.Models.Default
{
    public class Years_Of_Service_Data
    {
        public List<Years_Of_Service> YearsOfService { get; set; }
    }
}

这是我的Helper中的一些代码，我将数据库结果（Oracle Data Reader）读入我的Model实体（我已确认这些值已正确添加到TotalService＆amp; ; PurchasedorReinstatedService属性）：

            while (odr.Read())
            {
                Years_Of_Service yosRecord = new Years_Of_Service();

                yosRecord.Year = gh.GetSafeInt(odr, 0);
                yosRecord.ServiceCredited = gh.ConvertNullDecimal(odr.GetValue(1));
                yosRecord.Salary = gh.ConvertNullDecimal(odr.GetValue(2));
                yosRecord.CoveredEmployer = gh.GetSafeString(odr, 3);

                // Use the Default Info Model Class - At_A_Glance Model properties to fill these properties for text labels.
                yosRecord.TotalService = defInfoOasis.At_A_Glance.CreditTotal.ToString("N5");
                yosRecord.PurchasedorReinstatedService = defInfoOasis.At_A_Glance.TotalPurchase.ToString("N5");
                yos.Add(yosRecord);
            }

我现在需要的是将YearsOfService.yos个实体添加到List<Years_Of_Service> yosd列表中。有人对如何解决这个问题有任何想法吗？

以下是我在CustomControls中设置get / set下列出的模型的方法：

    private void GetDefaultInfoOasis()
    {
        DefaultInformation dio = new DefaultInformation);
        DefaultHelper dh = new DefaultHelper(Convert.ToInt32(Session["memberAccountId"]));

        dio = dh.GetDefaultInformation();

        // sets the Model Properties on the Custom Controls to that returned by [dio]
        AtAGlance.aag = dio.At_A_Glance;
        AnnualSalary.a_s = dio.Annual_Salary;
        YearsOfService.yos = dio.Years_Of_Service;

        // Attempting to add all or even 1 of the [dio.Years_Of_Service] or [YearsOfService.yos] (same thing) to the [YearsOfService.yosd] list:

        // Attempt 2: NULL Reference Exception
        YearsOfService.yosd.YearsOfService.Add(YearsOfService.yos.First());

        // Attempt 1: NULL Reference Exception
        YearsOfService.yosd.YearsOfService.Add(new Years_Of_Service { Salary = dio.Years_Of_Service.First().Salary, Year = dio.Years_Of_Service.First().Year, ServiceCredited = dio.Years_Of_Service.First().ServiceCredited, CoveredEmployer = dio.Years_Of_Service.First().CoveredEmployer, TotalService = dio.Years_Of_Service.First().TotalService, PurchasedorReinstatedService = dio.Years_Of_Service.First().PurchasedorReinstatedService });

        BeneficiaryDesignation.lb = dio.Beneficiaries;
    }

任何人都知道我错过了什么/做错了什么？这可能是获得我想要的长期迂回方式（目前将[TotalService]和[PurchasedorReinstatedService]的相同值添加到我的所有[Years_Of_Service]记录中），但这是我能想到的最简单的方法（不使用全局变量）在我的助手......）

Answer 1

我没有尝试将List<Years_Of_Service>.First()插入Years_Of_Service_Data，而是为我的自定义控件创建了一个常规Year_Of_Service实体，以便访问：

namespace PROJECT.CustomControls.Default
{
    public partial class YearsOfService : System.Web.UI.UserControl
    {
        public List<Years_Of_Service> lyos { get; set; }
        public Years_Of_Service y_o_s { get; set; }


        protected void Page_Load(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                ApplyData();
            }
        }

        private void ApplyData()
        {
            salaryGridView.DataSource = lyos;
            salaryGridView.DataBind();

            if (y_o_s.TotalService.ToString() != null)
            {
                creditSalLabel.Text = y_o_s.TotalService.ToString();
            }
            else
            {
                creditSalLabel.Text = String.Empty;
            }

            if (y_o_s.PurchasedorReinstatedService.ToString() != null)
            {
                purchaseCreditLabel.Text = y_o_s.PurchasedorReinstatedService.ToString();
            }
            else
            {
                purchaseCreditLabel.Text = String.Empty;
            }
        }
    }
}

我使用自定义控件的默认页面：

    private void GetDefaultInformation()
    {
        DefaultInformation dio = new DefaultInformation();

        DefaultHelper dh = new DefaultHelper(Convert.ToInt32(Session["memberAccountId"]));

        dio = dh.GetDefaultInformation();

        AtAGlance.aag = dio.At_A_Glance;
        AnnualSalary.a_s = dio.Annual_Salary;
        YearsOfService.lyos = dio.Years_Of_Service;
        YearsOfService.y_o_s = dio.Years_Of_Service.First();
    }

Answer 2

我不知道你在哪里初始化YearsOfService.yosd如果在执行此YearsOfService.yosd.YearsOfService.Add(...)之前该属性未设置为新对象，那么它将失败。

将First（）类实体添加到类实体的<list>？</list>

2 个答案: