ASP.NET & Databases Part 4
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ASP.NET & Databases : Part 4
Welcome to another part in ASP &
Databases, this time we are going to be looking at how to display our data in
or on something. We're going to be using the DataSet that we got in Part 3,
and for you lazy people who want to steal my code, here it is -
|<%@ Page Language="VB"
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.Oledb" %>
<script language="VB" runat="server">
Sub Page_Load(sender as object, e as eventargs)
Dim objConn as New OleDBConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data
Dim ds as Dataset = New DataSet()
Dim objAdapter as New OleDbDataAdapter("SELECT * FROM users", objConn)
Dim objCmdBld as New OleDbCommandBuilder(objAdapter)
'add any more code that I show you here. Don't close Tags yet.
|The Repeater Control|
I'll tell you now that all of these methods of
viewing data is tedious and very complicated, but I'm sure that you can work
it out, your relatively smart humans.
The Repeater is a control that loops through
the data and displays it on templates that you create.
- ItemTemplate. This is the template
where it displays the main body of the data.
- AlternativeItemTemplate. You can have
an alternating style for every second item if you want.
- HeaderTemplate. For any header you
- SeparatorTemplate. For separating
items (usually in the form of <br>, <hr> etc.).
- FooterTemplate. For footers!
Before I show you the code there is one thing
that I should tell you about.
DataBind() is a method that takes all of the
data on the page and binds it to the controls that you have specified for
The first line sets the datasource and the
second binds the data to the repeater, without binding, the data wouldn't be
Remember that this code just snaps on to the
one in the introduction.
<asp:repeater id="Rpt" runat="server">
<table border="0" cellspacing="1" cellpadding="3">
<td bgcolor="#6699FF" width="25%">Last Name</td>
<td bgcolor="#6699FF" width="25%">First Name</td>
<%# Container.DataItem("LName") %>
<%# Container.DataItem("FName") %>
Lets look at this in sections -
- We first set the repeater's datasource,
which is the datatable "users". DefaultView is the view of the table, we'll
look at views later (in another Part).
- Then we bind the data to the repeater.
- We start the repeater in the normal way to
start any Web Form Control.
- The HeaderTemplate starts a table
with 2 columns, First Name and Last Name.
- The ItemTemplate fills each column
with the appropriate data, 'Container refers to the DataSource, we'll talk
about that later (in another Part).
- Finally the FooterTemplate closes the
table and we then close up the remaining open tags.
I haven't put in any kind of Alternating Item
in here, but its simple enough.
That is all a Repeater can do, it presents data
and that is all there is to it.
|The DataList Control|
The DataList is very much like the Repeater but
the DataList supports editing of data. You use the templates like we did with
the repeater, but there are two new ones :
- SelectedItemTemplate. This is the
template the shows up when you select a row.
- EditItemTemplate. This is what shows
up when you select a row for editing.
Here is a very simple use of it.
dl_ItemCommand(sender as object, e as DataListCommandEventArgs)
dl.SelectedIndex = e.Item.ItemIndex
<asp:datalist id="dl" runat="server"
RepeatLayout = "table"
RepeatDirection = "vertical"
DataKeyField = "ID"
Last Name, click for full name.
<asp:linkbutton id="b1" runat="server" Text='<%#
Container.DataItem("LName") %>' CommandName = "select" />
<%# Container.DataItem("LName") & ", " &
This is a rather large piece of code, but here
is the explanation....
- After the databinding we put a new procedure
(this will be explained soon).
- We enclose the DataList in a form tag
because it needs to reload the page to select items.
- We define properties of the DataList -
- HeaderStyle-BackColor The
background of the Header (instead of putting it in the table code).
- SelectedItem-BackColor The
background of the Selected Item.
- RepeatLayout This is how the
DataList should be laid out - either 'table' or 'flow' (flow is just
nothing ie. You define exactly how you want it.)
- RepeatDirection The direction in
which to display the items (horizontal or vertical).
- DataKeyField The primary key to
use, this helps when selecting and editing data.
- OnItemCommand Explained Later.
- HeaderTemplate This is just a very
simple Header column.
- ItemTemplate The link button is a
link that serves as a submit type button (but text-only). You display the
Last Name and the CommandName of "Select" sends the command "Select" to the
DataList (which then performs whatever it needs to do.
- SelectedItemTemplate Shows the First
and Last Name.
- Then we close up everything
This is quite complicated and there are many
unexplained things, here is an explanation for one of them :
Most of these controls have events that happen
when you do something, like when you click on an item or automatic ones like
when an item is created. All of these events can have event handlers. In the
above example we used an event handler for the ItemCommand event. It takes in
the usually parameters with one difference - its DataListCommandEventArgs and
not EventArgs, this provides you with more properties that are specialized for
use with the DataList.
dl.SelectedIndex tells the DataList what Item
to put the selected template on.
e.Item.ItemIndex returns the index of the Item that was selected.
There are many more events for Data Viewers and
I hope to provide them in a future part.
But that wraps up the DataList, don't be afraid
to experiment with properties and ways to view data.
|The DataGrid Control|
This is probably the most powerful control, it
can go from simple to complex. I have already written an article on it but
there are a few things that I can show you with it that it didn't cover.
Instead of templates, the DataGrid has types of
- Bound Columns These allow you to
specify how a column is displayed, these are the default ones used by the
- Button Columns These columns have
buttons in them that can be customized.
- Edit Command Column This allows you
to edit items, when clicked it replaced the items with editable fields and
- Hyperlink Column A column with a
- Templated Column A custom column.
<asp:DataGrid id="dg" runat="server" />
This is the most simple form of viewing data in
a DataGrid, this creates a table with the column names equaling the names in
the actual DataTable and the information is just listed in rows, no special
formatting or anything.
<asp:DataGrid id="dg" runat="server"
<asp:label id="Name" runat="server" Text='<%#
Container.DataItem("FName") & " " & Container.DataItem("LName") %>' />
This is a bit more complicated, but not as bad
as it gets.
- After a Standard Databinding session we set
many properties of the DataGrid (self explanatory ones are left out)
- GridLines If you want to specify a
single way that the gridlines go, do it here.
- AutoGenerateColumns If this is true
it makes the columns up for you, if its false, it relies on your Columns
that you set up. If it is true and you have defined columns then it will
use both your columns and the Auto Generated ones.
- Next we start to put in columns.
- The BoundColumn for the ID Field
- A Template Column (you can see the template
that we're using here (the ItemTemplate)) and we then put a label on it.
- We close tags.
This is no where NEAR the amount of stuff you
can do on DataGrids, and because I like them, look out for an article -
And you thought DataSets were bad, In future
parts I will show you how to edit the data in the table, make them more
interactive, show you some more properties and techniques, and more stuff like
The amount of properties that you can set is
enormous. In Classic ASP it would have taken some time to set all of this up,
but now its simple (well, kind of simple).
You can experiment with properties and ways to
If you want to see more about the other columns
of a DataGrid see Part 6 (we're doing a quick Part on XML next).