Need to generate ASP.NET controls from a database

Question

I am writing an application where the controls for a page need to be determined from data in a Sql Server table.

For example: I have a PropertyGroups with Properties(Join Table) I then have categories to Propertygroups, the Properties have a values table, blah blah. Not to get too much in to the DB schema, but I need to assign controls to properties.

Like lets's say that property Color needs to be a listbox and the items collection is predetermined by the data in the database etc...

What is the most efficient way to render this before the page is loaded? A handler maybe? I am using Master Pages as well.

Is there a case where the color listbox may not exist or may not be rendered to the page? Similarly other controls? Or will the color listbox always exist? What about placement of controls in the general html tree? Do controls have their place in html but they may or may not exist? I think some html sample will help us understand what you're trying to do as well as what you've tried and what worked/didn't work (errors you see etc.) will be helpful in trying to understand what exactly you're trying to do and what trouble you've had — Shiv Kumar
– Shiv Kumar, Commented Feb 16, 2011 at 12:27
<asp:RadioButtonList ID="Property ID from DB" runat="server" RepeatLayout="UnorderedList"> <asp:ListItem>Property Value FROM DataSet</asp:ListItem> <asp:ListItem>Property Value FROM DataSet</asp:ListItem> <asp:ListItem>Property Value FROM DataSet</asp:ListItem> </asp:RadioButtonList> — CrazyCoderz
– CrazyCoderz, Commented Feb 16, 2011 at 12:35

gor · Accepted Answer · 2011-02-16 12:17:10Z

2

Retrieve all data from database.
Construct control tree in memory.
Add this tree to Page's Controls property.

Or, if you just need to render html, you can use some template engine, like NVelocity.

answered Feb 16, 2011 at 12:17

gor

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2 Comments

CrazyCoderz Over a year ago

You make this sound simple :) Could someone poast an example maybe? I am sortof creating my own template engine I guess.

Wyatt Barnett Over a year ago

We've got a site that does this (generate controls at runtime) sort of thing endemically. You don't want this. Use a templating engine.

t3rse · Accepted Answer · 2011-02-16 12:53:08Z

Although you can dynamically load controls and add them to the Page class Controls collection, it seems to me that the best solution for your problem is to take advantage of some kind of template bound control that gives you control on the datatemplate. You can structure the template with the controls you want added to the page and they will be repeated based on the data you are binding to.

A simple example with a Repeater control might look as follows:

<asp:Repeater id="dataRepeater" runat="server">
  <ItemTemplate>
     <asp:ListBox id="myList" runat="server" />
     <asp:TextBox id="myText" runat="server" Text='<%#Eval("MyDataField")%>' />
     <div> Plain Html </div>
  </ItemTemplate>
</asp:Repeater>

You have the ability to have alternating item templates. Also, with hierarchical data, you can make a couple of passes at the Item which your Repeater is binding to. For example, assuming I wanted to bind the ListBox to a collection of its own, I could bind the Repeater and then make another pass at the Items collection, use the FindControl method to find my ListBox and then act on it's own DataSource.

        foreach (var item in dataRepeater.Items) 
        {
            var listBox = item.FindControl("myList") as ListBox;
            listBox.DataSource = moreData;
            listBox.DataTextField = "Text";
            listBox.DataValueField = "Value";
            listBox.DataBind();
        }

The Repeater, DataList and other template bound controls support events too, things like ItemDataBound that you can use to operate on your templates as well. You can do things like toggle visibility of controls that are already in the template or insert a child control if you want to have control over what is inside each template item based on what's in your database.

As noted above, you can use some other template engine but the concept would be fairly similar. The idea is that you allow your template to drive the HTML that is rendered as opposed to trying to operate and manage the control tree yourself.

Dan Hedges · Accepted Answer · 2011-02-16 13:28:57Z

If you add a placeholder control in your .aspx file, a bit like this...

<body>
    <form id="form1" runat="server">
    <div>
        <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>
    </div>
    </form>
</body>

... then you will be able to create controls in memory and add them to the controls collection of the placeholder, a simple example might be...

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        this.PlaceHolder1.Controls.Add(new Button(){
            Text = "Added"}
        );

    }
}

... although this just adds a button, there is no reason you could not add any type of control and just retrieve the values for it from a database.

Dan.

gor · Accepted Answer · 2011-02-16 13:03:38Z

0

And it looks like, you problem can be easily solved with asp.net mvc (just define view and model), or even Dynamic Data.

answered Feb 16, 2011 at 13:03

gor

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