Question

Each time when pressing tree node then selectegNodeChanged event triggered and page is reloaded.So, i lost some data stored in Dictionary,ArrayList…How to prevent those data losing?

So, I stored those Dictionary and ArrayList as “static”.It is now resolved my problem.

Is it good way to do that?

Answer 1

No. Do not use static. Try to store these in ViewState or Session instead.
You can consider ViewState if it is not a large amount of data.
static will be accessible across Session and is not a good practice.

You can create properties and avoid code duplication like shown below.

    public ArrayList TreeNodeDataList
    {
        set
        {
            ViewState["TreeNodeDataList"] = value;
        }
        get
        {
            if (ViewState["TreeNodeDataList"] == null)
            {
                return (new ArrayList());
            }
            else
            {
                return (ViewState["TreeNodeDataList"] as ArrayList);
            }
        }
    }

Now, when you want to re-assign data, read TreeNodeDataList property. If count of that ArrayList is 0, fetch from DB, else use it.

Hope I am clear enough.