Question

我正在使用Visual Studio 2010和SQL SERVER管理工作室2008 R2

我有一张表格参考表格预订

CREATE TABLE [Order]
(OrderNumber int IDENTITY (1,1) NOT NULL PRIMARY KEY,
CustNumber int FOREIGN KEY REFERENCES Customer(CustNumber),
EmpNumber int FOREIGN KEY REFERENCES Employee(EmpNumber),
OrderDate date,
Deliver char,
StatusID int FOREIGN KEY REFERENCES [Status] (StatusID),
BookingNumber int FOREIGN KEY REFERENCES Booking(BookingNumber),
TotalAmount float,
OutstandingAmount float);
GO

CREATE TABLE Booking
(BookingNumber int IDENTITY (1,1) NOT NULL PRIMARY KEY,
BookingDate datetime,
BookingTime datetime,
StatusID int FOREIGN KEY REFERENCES [Status](StatusID),
CustNumber int FOREIGN KEY  REFERENCES Customer(CustNumber),
EmpNumber int FOREIGN KEY REFERENCES Employee(EmpNumber)
);
GO

我还有一个继承orderClass

的Order类和ClassList OrderList

 public class Order
{
    public int OrderNumber { set; get;}
    public int CustNumber { set; get;}
    public int EmpNumber { set; get;}
    public DateTime OrderDate { set; get;}
    public char Deliver { set; get;}
    public int StatusID { set; get;}
    public int BookingNumber { set; get; }
    public float TotalAmount { set; get;}
    public float OutstandingAmount { set; get; }


  public Order()
    {
        OrderNumber = 0;
        CustNumber = 0;
        EmpNumber = 0;
        OrderDate = DateTime.Today;
        Deliver = ' ';
        StatusID = 0;
        BookingNumber = 0;
        TotalAmount = 0;
        OutstandingAmount = 0;

    }

    public Order(int a, int b, int c, DateTime d, char e,int f, int g, float h, float i)
    {
        OrderNumber = a;
        CustNumber = b;
        EmpNumber = c;
        OrderDate = d;
        Deliver = e;
        StatusID = f;
        BookingNumber = g;
        TotalAmount = h;
        OutstandingAmount = i;

    }
namespace EAMS_BusinessTier
{
public class OrderList : System.ComponentModel.BindingList <Order>
{private EAMS_DBDataSetTableAdapters.OrderTableAdapter OrderTA = new EAMS_DBDataSetTableAdapters.OrderTableAdapter();
    private EAMS_DBDataSet ds = new EAMS_DBDataSet();


    /////////// Read OrderList //////////////////////////
    public OrderList()
    {
        OrderTA.FillbyOrder(ds.Order);
        foreach (EAMS_DBDataSet.OrderRow r in ds.Order.Rows)
        {
            Order m = new Order(r.OrderNumber,r.CustNumber,r.EmpNumber,r.OrderDate,Convert.ToChar(r.Deliver),r.StatusID,r.BookingNumber,Convert.ToInt32(r.TotalAmount),Convert.ToInt32(r.OutstandingAmount));
            this.Add(m);
        }
    }

    public OrderList(int id)
    {
        OrderTA.FillbyOrder(ds.Order);
        foreach (EAMS_DBDataSet.OrderRow r in ds.Order.Rows)
        {
            if (id == r.OrderNumber)
            {
                Order m = new Order(r.OrderNumber, r.CustNumber, r.EmpNumber, r.OrderDate, Convert.ToChar(r.Deliver), r.StatusID, r.BookingNumber, Convert.ToInt32(r.TotalAmount), Convert.ToInt32(r.OutstandingAmount));
                this.Add(m);
            }
        }
    }
    /////END////


    ///////////////////// get OrderList ////////////////////////
    public OrderList getOrderList()
    {

        return this;
    }

    public OrderList getOrderList(int id)
    {
        OrderList t = new OrderList(id);
        return t;
    }
    ////END////


    /////////////////////  Save Order ////////////////////////
    public void SaveOrder()
    {
        EAMS_DBDataSet.BankDataTable temp = new EAMS_DBDataSet.BankDataTable();

        foreach (Order r in this)
        {
            EAMS_DBDataSet.OrderRow nr = ds.Order.NewOrderRow();
            nr.OrderNumber = r.OrderNumber;
            nr.CustNumber = r.CustNumber;
            nr.EmpNumber = r.EmpNumber;
            nr.OrderDate = r.OrderDate;
            nr.Deliver = Convert.ToString(r.Deliver);
            nr.StatusID = r.StatusID;
            nr.BookingNumber = r.BookingNumber;
            nr.TotalAmount = r.TotalAmount;
            nr.OutstandingAmount = r.OutstandingAmount;


            temp.Rows.Add(nr.ItemArray);
        }

        ds.Order.Merge(temp, false);

        foreach (EAMS_DBDataSet.OrderRow r in ds.Order.Rows)

            if (r.RowState == DataRowState.Unchanged)
            {
                r.Delete();
            }

        OrderTA.Update(ds.Order);
    }
    ////END////


    //////////////// Insert Order //////////////////////////////
    public void InsertOrder(int a, int b, int c, DateTime d, char e, int f,int g,float h,float i)
    {
        Order m = new Order(a, b, c, d, e, f, g, h, i);
        this.Add(m);
    }
    ////END////



    /////////////////Delete Order /////////////////////////
    public void DeleteOrder(int del)
    {
        int i = 0;
        int d = -1;

        foreach (Order r in this)
        {
            if (r.OrderNumber == del)
            {
                d = i;
            }
            i++;
        }
        if (d > -1)
        {
            this.RemoveAt(d);
        }
    }
    ////END////


    /////////////// Update Order ///////////////////////
    public void UpdateOrder(int a, int b, int c, DateTime d, char e, int f, int g, float h, float i)
    {
        Order r = new Order(a, b, c, d, e, f, g, h, i);
        foreach (Order nr in this)
        {
            if (r.OrderNumber == nr.OrderNumber)
            {
                nr.OrderNumber = r.OrderNumber;
                nr.CustNumber = r.CustNumber;
                nr.OrderDate = r.OrderDate;
                nr.Deliver = r.Deliver;
                nr.StatusID = r.StatusID;
                nr.BookingNumber = r.BookingNumber;
                nr.TotalAmount = r.TotalAmount;
                nr.OutstandingAmount = r.OutstandingAmount;


                break;
            }
        }
    }
    ////END////

这必须起作用的方式并非每个订单都有预订编号，因此订单表中的预订编号可以为空值。

当我在构建业务层并连接到OrderList Data对象后尝试在表示层中加载OrderList时，会发生错误。这是我用来从表示层加载OrderList的代码

using EAMS_BusinessTier;

namespace DXApplication2
{
public partial class Form5 : Form
{
    public Form5()
    {
        InitializeComponent();
    }
    internal OrderList OrderLis = new OrderList();
    private void Form5_Load(object sender, EventArgs e)
    {
        orderListBindingSource.DataSource = OrderLis;
    }

当我尝试在运行时加载OrderList时，我继续收到此错误＆＃34;列＆＃39; BookingNumber＆＃39;的值在表格＆＃39;订单＆＃39;是DBNull。＆＃34;我该如何处理这个错误？

提前谢谢

Answer 1

将Order.BookingNumber的类型从int更改为Nullable<int>。或者只是int?。

验证您的EDM。表Order中的BookingNumber字段必须允许空值。

更改

Order m = new Order(r.OrderNumber,r.CustNumber,r.EmpNumber,r.OrderDate,Convert.ToChar(r.Deliver),r.StatusID,r.BookingNumber,Convert.ToInt32(r.TotalAmount),Convert.ToInt32(r.OutstandingAmount));

为：

Order m = new Order(r.OrderNumber,r.CustNumber,r.EmpNumber,r.OrderDate,Convert.ToChar(r.Deliver),r.StatusID,(int?)r.BookingNumber,Convert.ToInt32(r.TotalAmount),Convert.ToInt32(r.OutstandingAmount));

错误：表中列的值是C＃Business Tier的DBNull

1 个答案: