WPF和ADO.NET上的项目

Question

I have a couple of problems in a project I need to make.

1. Project has to have listed all the table data(auctions) in a listbox and when a user wants to bid for a certain bid he can select the bid from the listbox and click Bid button.
2. When the Bid button is pressed it needs to increase value of the bid by one and it needs to write the name of the user who is biding.

3. I have created update statements in bid button event, but it doesnt work properly, it just stays as it is with no change.

   Also how can I implement that the bid button works only on selected item in a listbox ?

My code:

public MainWindow()
{
  InitializeComponent();
  tmr.Interval = new TimeSpan(0, 0, 1);
  tmr.Tick += tmr_Tick;
  showData sd = new showData();
  sd.ToString();
  listBox1.Items.Add(sd.ToString());

}


private void btn_Click(object sender, RoutedEventArgs e)
{
  string user = "test";
  int a = +1 ;
  using (SqlConnection conn = new SqlConnection(@" Data source=ALASAD; Initial Catalog=aukcija_Arsen_Milosev; Integrated Security = true;"))
  {
    conn.Open();
    using (SqlCommand comm = new SqlCommand("UPDATE auctions SET bidValue = @bidvalue, lastBider = @lastbider",conn))
    {
      comm.Parameters.AddWithValue("@lastbider", user);
      comm.Parameters.AddWithValue("@bidValue", a);
      comm.ExecuteNonQuery();
      conn.Close();
    }

  }
  listBox1.Items.Clear();
  showData sd = new showData();
  sd.ToString();
  listBox1.Items.Add(sd.ToString());
}

Answer 1

Following MVVM pattern you should expose in the ViewModel properties for User and SelectedAuction. And bind the properties to ListBox in XAML

XAML would be like this "ListBox Items={Binding Auctions} SelectedItem={Binding Auction} />"
"Button Command={Binding Bid} />"

And ViewModel

using MicroMvvm;

public AuctionsViewModel : ObservableObject
{
    private string user;
    private int auction;
    private ObservableCollection<int> auctions;

    public string User
    {
        get{return user;}
        set         
        {
            if(user!=value)
            {
                user=value;
                RaisePropertyChanged("User");
            }               
        }
    }

    public int Auction
    {
        get{return auction;}
        set         
        {
            if(auction!=value)
            {
                auction=value;
                RaisePropertyChanged("Auction");
            }               
        }
    }

    public ObservableCollection<int> Auctions
    {
        get{return auctions;}
        set         
        {
            if(auctions!=value)
            {
                auctions=value;
                RaisePropertyChanged("Auctions");
            }               
        }
    }

    public ICommand Bid
    {
        get{return new RelayCommand(BidExecute);}
    }

    private void BidExecute()
    {
        Auction++;
        using (SqlConnection conn = new SqlConnection(@" Data source=ALASAD; Initial Catalog=aukcija_Arsen_Milosev; Integrated Security = true;"))
        {
            conn.Open();
            using (SqlCommand comm = new SqlCommand("UPDATE auctions SET bidValue = @bidvalue, lastBider = @lastbider",conn))
            {
                comm.Parameters.AddWithValue("@lastbider", User);
                comm.Parameters.AddWithValue("@bidValue", Auction);
                comm.ExecuteNonQuery();
                conn.Close();
            }
        }
        Auctions.clear();           
        showData sd = new showData();
        Auctions.AddRange(sd.toString());
        RaisePropertyChanged("Auctions");
    }
}