我创建了Auction.cs
带有以下代码的类:
namespace WebApplication5
{
public class Auction
{
public string Productname { get; set; }
public string Lastbidder { get; set; }
public int Bidvalue { get; set; }
private List<Auction> listaAukcija = new List<Auction>();
public List<Auction> ListaAukcija
{
get { return listaAukcija; }
set { listaAukcija = value; }
}
public void getAll()
{
using (SqlConnection conn = new SqlConnection(@"data source=JOVAN-PC;database=aukcija_jovan_gajic;integrated security=true;"))
{
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = @"SELECT a.id AS aid, p.name AS pn, u.name AS un, a.lastbid AS alb FROM (Auction a INNER JOIN Product p ON a.productid = p.id) INNER JOIN User u ON a.lastbider = u.id";
conn.Open();
using (SqlDataReader reader = cmd.ExecuteReader())
{
listaAukcija.Clear();
while (reader.Read())
{
Auction auction = new Auction();
if (reader["aid"] as int? != null)
{
auction.Productname = reader["pn"] as string;
auction.Lastbidder = reader["un"] as string;
auction.Bidvalue = (int)reader["alb"];
}
listaAukcija.Add(auction);
}
}
}
}
public override string ToString()
{
return base.ToString();
}
}
}
我在另一个类中称它为方法DbBroker.cs
:
public class DbBroker : Home
{
Auction aukcija = new Auction();
public void executeQuery()
{
aukcija.getAll();
}
public void getArr()
{
List<string[]> lista = aukcija.ListaAukcija.Cast<string[]>().ToList();
var x = ListBox1.Text;
x = lista.ToString();
}
}
并getArr
在Home
页面上调用:
public partial class Home : System.Web.UI.Page
{
DbBroker dbb = new DbBroker();
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Label3.Text = Session["Username"].ToString();
dbb.getArr();
}
}
}
问题是,我在课堂StackOverflowException
上遇到错误。我不知道为什么或如何解决。Auction aukcija = new Auction();
DbBroker.cs
您正在Auctions
自身= Stackoverflow中创建对象列表。
这是你的问题:
public class Auction {
private List<Auction> listaAukcija = new List<Auction>();
}
您将需要将Auction
模型与获取数据的服务或存储库分开。
例如:
//the model
public class Auction {
public string Productname { get; set; }
public string Lastbidder { get; set; }
public int Bidvalue { get; set; }
public override string ToString()
{
return base.ToString();
}
}
//the service (or can replace this with a repository)
public class AuctionService {
private List<Auction> listaAukcija = new List<Auction>();
public List<Auction> ListaAukcija
{
get { return listaAukcija; }
set { listaAukcija = value; }
}
public void getAll()
{
//get the data and populate the list
}
}
更新
您将需要AuctionService
在DbBroker中实例化。DbBroker
不再继承Home
(注释掉)。
public class DbBroker //: Home <-- circular reference
{
AuctionService auctionService = new AuctionService();
public void executeQuery()
{
auctionService.getAll();
}
public void getArr()
{
string[] lista = auctionService.ListaAukcija.ConvertAll(obj => obj.ToString()).ToArray();
ListBox1.Text = string.Join("\n", lista);
}
}
在Page_Load()上-您没有调用executeQuery()函数来填充列表。
public partial class Home : System.Web.UI.Page
{
DbBroker dbb = new DbBroker();
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Label3.Text = Session["Username"].ToString();
dbb.executeQuery(); //populate list.
dbb.getArr(); //convert to string and update textbox
}
}
}
PS。有了新的更新,AuctionService实际上应该是存储库,而DbBroker可以充当Service层。但是,这仍然可以用于教育目的。
我希望这有帮助。
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