New Criteria On Postback

post_id: 30 / post_date: 2010-12-03

Assume you need to have a webform where any number of criteria can be added. Criteria is a set of input fields and N number can be added.

We can use an asp-repeater for this. The problem is catching the add button postback and retrieving 1-n sets of fields from the input

We can do this with 3 smart methods.

    protected void Page_Load(object sender, EventArgs e)
        var addClicked = Request.Params["__EVENTTARGET"] == AddMore.ClientID;
        var items = ReadFields();
        if (items.Count == 0 || addClicked) items.Add(NewItem());
        Fields.DataSource = items;
        if (Names.Count == 0) AddMore.Visible = false;

	private List ReadFields()
		var result = new List();
		var index = 0;

		var name = string.Format("Fields$ctl{0}$name",index.ToString("D2"));
		if ((name = Request[name]) != null)
			var i = NewItem();
			i.SelectedName = name;
			index += 2; //because of separator
            Names.Remove(name); //remove only after creating item instance
            goto loop;
		return result;

	protected void Fields_ItemDataBound(object sender, RepeaterItemEventArgs e)
		if (e.Item.ItemType == ListItemType.Separator) return;
		var i = e.Item.DataItem as Item;
		var ctl = e.Item.FindControl("name") as DropDownList;
		i.Names.Insert(0, "");
		ctl.DataSource = i.Names;
        if (!string.IsNullOrEmpty(i.SelectedName) && i.Names.Contains(i.SelectedName)) ctl.SelectedValue = i.SelectedName;

Thats the core of it. See the web and aspx files.