How to generate and process multiple checklistboxes

Gurus,

I've been searching for a clear example on how I can go about processing multiple, varying categories of items with C# in ASP.NET. The data is similar to the following:

Category1 Heading
  Item
  Item
  Item

Category2 Heading
  Item
  Item
  Item
Category3 Heading
  Item
  Item
开发者_运维问答  Item

The category names and items come from a SQL database. I imagine I'll need one checkboxlist for each category of items and the number of categories is dynamic and will change over time. Is it possible to create a loop to dynamically build the required checkboxlists and then be able to process them? I read about maybe using a data repeater as well. Any assistance is greatly appreciated.

You could use a repeater or a DataGrid. Occasionally it's easier for me to use a DataGrid and just add rows for each new Category. Do you have any more specifics on what you're looking to do with it?

You could use a DataGrid and for each category add a new row. And within that row add Controls. A less savvy way would be to use a PlaceHolder on the page and just add controls to that. But I would definitely suggest a DataGrid or looking into the Repeater.

You could try something like this...

Your business object. You may use this as a model you can transform from your 'real' business object or use your business object directly

public class BusinessObject
{
    public string Category { get; set; }  //Your category
    public int ID { get; set; }           //Point of data entry and will be return on post
    public string Name { get; set; }      //A friendly name for your users
}

Your aspx markup. I'm using a repeater for the categories which just has a CheckBoxList in it which will have the actual items. This can be expanded and styled quite a bit.

<asp:Repeater ID="myRepeater" runat="server">
    <ItemTemplate>
        <asp:CheckBoxList ID="checkboxlist" 
                          runat="server" 
                          DataTextField="Name" 
                          DataValueField="ID" />
    </ItemTemplate>
</asp:Repeater>

A Place to get your business objects from: Here I just have a member on my codebehind. You should grab this data from your business layer/tier.

List<BusinessObject> MyBusinessObjects = new List<BusinessObject>();

And your code behind

    protected void Page_Load(object sender, EventArgs e)
    {
        //Wire up the event to handle when items are bound to the repeater
        this.myRepeater.ItemDataBound += new RepeaterItemEventHandler(myRepeater_ItemDataBound);
        //Now actually bind the categories to the repeater
        this.myRepeater.DataSource = GetCategories(MyBusinessObjects);
        this.myRepeater.DataBind();
    }

    void myRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
    {
        //Don't process items that are not item, or alternating item
        if (!(e.Item.ItemType == ListItemType.AlternatingItem || e.Item.ItemType == ListItemType.Item)) return;
        //Grab a reference to the checkboxlist in our repeater
        CheckBoxList checkboxlist = (CheckBoxList)e.Item.FindControl("checkboxlist");
        //Now put our business objects of that category in it
        checkboxlist.DataSource = GetItemsFromCategory(MyBusinessObjects, (string)e.Item.DataItem);
        checkboxlist.DataBind();
    }
    //Helper to grab categories.
    private IEnumerable<string> GetCategories(IEnumerable<BusinessObject> items)
    {
        return (from i in items
                select i.Category).Distinct();
    }
    //Helper to grab the items in categories.
    private IEnumerable<BusinessObject> GetItemsFromCategory(IEnumerable<BusinessObject> items, string category)
    {
        return (from i in items
                where i.Category == category
                select i);
    }

If you don't know in advance how many items there could be, then you need a display that will not break. The best way to achieve this is by using a ListView with a GroupTemplate:

http://forums.asp.net/t/1364813.aspx/1

just imagine that this is your data structure. To do without repeaters.

var list = new Dictionary<string, List<string>>
                           {
                               {"Name1", new List {"item1", "item2", "item3"}},
                               {"Name2", new List {"item1", "item2", "item3"}},
                               {"Name3", new List {"item1", "item2", "item3"}},
                               {"Name4", new List {"item1", "item2", "item3"}},
                               {"Name5", new List {"item1", "item2", "item3"}}
                           };

            foreach (var category in list)
            {
                var checkBoxList = new CheckBoxList
                                       {
                                           Text = category.Key
                                       };

                foreach (var value in category.Value)
                {
                    var listItem = new ListItem(value);
                    checkBoxList.Items.Add(listItem);
                }
            }

Thanks again to everyone for the help. We ended up changing the requirements and a single checkboxlist will now suffice. I think the dynamic addition of the checkboxlists to a placeholder would have worked though.