Question

hello i m doing a very simple Asp.net application project

 namespace WebApplication1
 {
 public partial class WebUserControl1 : System.Web.UI.UserControl
 {
    market m = new market();

    protected void Page_Load(object sender, EventArgs e)
    {


    }
    protected void button_clickSell(object sender, EventArgs e) 
    {


        float price = float.Parse(this.BoxIdPrezzo.Text);

        m.insertProd("xxx", 10, "yyy");
        m.addOfferForProd("ooo", 5, "gggg");
        m.insertProd(this.BoxIdDescrizione.Text,price,this.BoxIdUtente.Text);
        String s;
        m.outMarket(out s);  
        this.Output.Text = s;  //the output here work good
        this.Output.Visible = true;

    }
    protected void button_clickView(object sender, EventArgs e) 
    {
        String s;
        m.outMarket(out s);
        this.Output.Text = s;  // here seem to have lost the reference to product why?
        this.Output.Visible = true;
    }
}
}

the problem is that when i click on button1 which call button_clickSell everything works good but when i click on button2 which call button_clickView products seem to not be anymore in the Market object, but this is pretty strange because in market object i have a list of product and m.outMarket in the first time work propely.

Answer 1

That is because of how pages work. Every time you make a request or a post-back to the page the values will be lost in that variable.

You will need to hold that in a session or something similar.

Here is a very basic example of using a session.

    protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["Collection"] == null)
        {
            Session["Collection"] = new List<int>();
        }//if
    }
    protected void button_clickSell(object sender, EventArgs e)
    {
        List<int> collection = (List<int>)Session["Collection"];
        collection.Add(7);
        collection.Add(9);
    }
    protected void button_clickView(object sender, EventArgs e)
    {
        List<int> collection = (List<int>)Session["Collection"];
        collection.Add(10);
    }