Published: Friday, July 27, 2001
Creating a DataBound List of Radio Buttons
By Scott Mitchell
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This article examines how to create a databound listbox using ASP.NET. For more information
on ASP.NET be sure to check out the articles in the
ASP.NET Article Index. The code in this article
is based on the Beta 2 version of ASP.NET. To learn more about the free ASP.NET Beta 2, be sure
to check out this FAQ.
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Introduction
A common task Web developers face is creating a form element (such as a series of checkboxes,
radio buttons, or a listbox) whose members are populated by the contents of a database table.
This is quite possible (and quite easy) to accomplish with ASP.NET In fact, in a previous
article (Creating Databound DropDown
Lists in ASP.NET), we examined how to create a databound listbox. In this article, we'll
examine how to create a series of radio buttons whose values are automagically populated from
a database table! We'll also look at how to respond to the user selecting a particular option
and showing more detailed information based upon the radio button selected.
The Impetus
On 4Guys there is a Sample On-Line Chapters page, which lists
a number of books that have free, on-line sample chapters. All of this information is stored
in a database that contains two tables: tblPublishers and tblBooks.
The tblPublishers contains a row for each publisher that has a book that appears
in the sample chapters listing, while the tblBooks table contains a row for each
sample book. Note that the tblBooks table contains a PublisherID
column which serves as a foreign key to the tblPublishers table, tying a particular
publisher to a particular book.
Wouldn't it be nice to generate a list of radio buttons based upon the publishers in the
tblPublishers table? From this list, the user could select a particular publisher,
at which point, the user would be shown a listing of books published by that particular publisher.
In creating the radio button list, we could hard code the list of publishers, but that would
be subject to change any time we added or removed publishers from the tblPublishers table.
Ideally, the radio button list would be dynamically generated based upon the values in
the tblPublishers table.
If you'd like to see what the end result will look like, check out the
live
demo. Pretty nice looking, eh? Realize that the radio button list was created dynamically
using databind (essentially three lines of code in total). And this entire page, from start
to finish, took me about four minutes to write. (I type fast. :-))
Creating the Databound Radio Button List
Creating a databound series of radio buttons is painfully simply with ASP.NET. We only really
need to do three things:
- Create the
asp:radiobuttonlist Web control, specifying the database columns
we want to bind to the radio buttons' displayed text values and the hidden values that are
passed along when the form is submitted.
- Write the code to populate a DataReader (or DataSet) with the applicable database information.
- Databind the DataReader (or DataSet) to the
asp:radiobuttonlist Web control
That's it! So, let's examine each of these three steps. First, create the needed Web control
in the HTML section of your ASP.NET Web page.
<html>
<body>
<form runat="server">
<b>Choose a Publisher's Books to View</b><br>
<asp:radiobuttonlist id="radlstPubs" runat="server"
DataValueField="PublisherID" DataTextField="Name" />
</form>
</body>
</html>
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The two most important things to notice is that we set the asp:radiobuttonlist
Web control's DataValueField and DataTextField properties. Both
properties should map to a column name in the database table that we wish to bind the radio
button list to. The DataTextField property are the names that will be visually
displayed next to each radio button; the DataValueField are the hidden values
that are associated with each radio button. Also note that the radio button list was placed
within a WebForm (the form tag with a runat="server" attribute).
Now that we've tackled our first step, let's look at performing our remaining two steps:
reading the database table tblPublishers into a DataReader and binding the
populated DataReader to the radio button list!
<% @Import Namespace="System.Data" %>
<% @Import Namespace="System.Data.SqlClient" %>
<script language="vb" runat="server">
Sub Page_Load(sender as Object, e as EventArgs)
If Not Page.IsPostBack then
'*** STEP 1: Populate a DataReader ***
'Create a connection
Dim myConnection as New _
SqlConnection(ConfigurationSettings.AppSettings("connectionString"))
'Create the command object, passing in the SQL string
Const strSQL as String = "SELECT PublisherID, Name FROM tblPublishers"
Dim myCommand as New SqlCommand(strSQL, myConnection)
'Open the connection and set the DataSource to the
myConnection.Open()
'Populate the datareader
Dim myDataReader as SqlDataReader
myDataReader = myCommand.ExecuteReader(CommandBehavior.CloseConnection)
'*** STEP 2: Bind the DataReader to radlstPubs ***
radlstPubs.DataSource = myDataReader
radlstPubs.DataBind()
End If
End Sub
...
</script>
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In the above Page_Load event handler we accomplish our two steps: populating a
DataReader (in this case a SqlDataReader) with the contents of the
tblPublishers table; and binding the resulting DataReader to our radio button list,
radlstPubs. Note that we only wish to run this binding code on the first visit
to the page (more on why later), hence we only perform the databinding if Page.IsPostBack
is False, meaning that the page has not yet been posted back.
Now that we've looked at how to create a databound radio button list, let's turn our attention
to responding to the user's selection of a particular radio button. In Part 2
we'll examine this aspect and the remainder of our application!
Read Part 2!
