如何防止asp.net页面重置数据表？

Question

Consider this code

    DataTable dt = new DataTable() ; 
    protected void Page_Load(object sender, EventArgs e)
    {
            dt.Columns.Add("RowIndex");
            dt.Columns.Add("FilterText");
    }

I will Fill this data table by some data during executing program. but when i click a button , the page will reload the codes and my data will be lost. how can i prevent the web form from creating new data table and save my data?

my controls are inside an update panel.

Answer 1

A new instance of the class is created for each request. If you want to save things from one request to another you need to use a different mechanism.

For example a global. But on top of a globals usual problems you need to handle multiple concurrent requests and thus multi-threading and locking.

The usual approach is to store persistent state in a database, loading the information for each request at the start of processing that request.

Answer 2

You can use View State to solve problem..

DataTable dt;

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
           dt = new DataTable();
           dt.Columns.Add("RowIndex");
           dt.Columns.Add("FilterText");
        }
        else
        {
            if (ViewState["vsDT"] != null)
                dt= ViewState["vsDT"] as DataTable;
        }
    }