How to hold a table of data for user edition (before saving in the the database)?

I've been using this programming style, that I've seen in an example and just started using it, because it does the job... I would like to know other programmers' opinion about it...

So the situation is when you have a GridView, or a control based on it like the RadGrid, and you want to keep track of a data table while you are adding, editing, reordering and deleting rows.

Using the session to hold the data table (or list of data) may not be the best solution, because the user may open two identical web pages… Using the ViewState to hold the data may be and option... I have been using an approach like the following:

public partial class DefaultPage : System.Web.UI.Page
{
    protected DataLine DefaultDataLine()
    {
        DataLine dl = new DataLine();

        dl = new DataLine();
        dl.Number = 0;
        dl.Title = "";
        dl.Text = "";
        return dl;
    }

    protected class DataLine
    {
        public int Number { get; set; }
        public string Title { get; set; }
        public string Text { get; set; }
    }

    protected static List<DataLine> tempLines;

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            tempLines = RadGridBi开发者_如何学编程ndStartUpData();
        }
    }

    protected void RadGrid1_NeedDataSource(object source, Telerik.Web.UI.GridNeedDataSourceEventArgs e)
    {
        RadGrid1.DataSource = tempLines;
    }

    protected void RadGrid1_InsertCommand(object source, Telerik.Web.UI.GridCommandEventArgs e)
    {
        GridEditableItem editedItem = e.Item as GridEditableItem;

        List<DataLine> table = tempLines;

        DataLine newRow = new DataLine ();

        RadTextBox rtb;   
        rtb = (RadTextBox)editedItem.FindControl("RadTextBoxTitle");
        newRow.Title = rtb.Text;
        rtb = (RadTextBox)editedItem.FindControl("RadTextBoxDescription");
        newRow.Description = rtb.Text;

        RadNumericTextBox number =  (RadNumericTextBox)editedItem.FindControl("RadNumericTextBoxNumber");
        newRow.Number = number.Value.HasValue ? Convert.ToInt32(number.Value.Value) : 0; 

        table.Add(newRow); 
    }

    // ...

So using a static List variable, of a custom object (class), declared in the code-behind of the Aspx page, and updating it whenever the data is edited.

What are your thoughts about this approach? Is it okay? How do you hold your table-format data for edition (prior to saving it in the database)?

Not exactly sure what you're going for, but using a static variable is probably not what you want to do. Static properties are shared across all user/threads, so all concurrent users would be editing the same data.

If you are just looking to persist a small data set across post-backs to the same page, use the ViewState instead. Just be mindful of potential performance issues if you plan on cramming lots of data into it.

It depends on what you're wanting to achieve

Viewstate will keep the data on that page - it won't be available on any other pages (or tabs, or windows)

Session will keep the data on the server, this means it will be available for any page the user is looking at (on your site) and it will keep it until the session times out.

Theres a lot of advtanges/disadvantages to either method, therefore you need to research your situation, here is a start.

You mentioned storing in the session, and how this could cause issues if the user opens up multiple copies of the page, etc...

We had a similar issue so I made a property in code behind on the page and on first page load (if not postback blah blah) I generate a new guid. Then I use the guid value as my session key and I know it'll be unique per page.

You could make a spify property like this...

Public ReadOnly Property SessionDataKey() As String
    Get
        If ViewState("SessionDataKey") Is Nothing Then
            ViewState("SessionDataKey") = Guid.NewGuid()
        End If

        Return ViewState("SessionDataKey").ToString()
    End Get
End Property

But in short, I just use the session.

Thank you very much for your replies! With your help, and some research, I see that both approaches, storing in session or using the static variable are indeed wrong, at least for the purpose I was using them... All your answers were helpful, and although I can only mark one as correct, I would like to leave my appreciation.

Well, for anyone stumbling across the same problem, here’s what I’ve implemented in my pages:

public partial class ScriptAdd : System.Web.UI.Page
{
    private List<MyItem> tempMyItems
    {
        get
        {
            //if (ViewState["tempMyItemsList"] == null)
            //    ViewState["tempMyItemsList"] = new List<MyItem>();

            return (List<MyItem>)ViewState["tempMyItemsList"];
        }
        set
        {
            ViewState.Add("tempMyItemsList", value);
        }
    }        

    protected void Page_Load(object sender, EventArgs e)
    {
        // ...
    }
}

And then use it whenever I want to add / insert / update lines to my temporary list:

        List<MyItem> table = tempMyItems;

        table.RemoveAt(idx);

        MyItem newRow = new MyItem ();

        // ...

        table.Insert(idx, newRow);

Finally, if intended, I store all the items in the database.