With all the ASP.NET samples I've been writing recently, I
decided I should spend some time working on the publishing
process. It sucks... for both myself and for our readers.
It currently takes me almost as long to publish a sample
as it does to write one! There are so many places I have
to change things that I always forget one of two. Anyway
that's where this code comes from.
I was looking for an easy way to publish the source code to
the ASP.NET samples running on our site, but like our
classic ASP samples, I wanted the code to come from the
script itself. Here's the temporary solution I'm using
while I get everything else working. It doesn't do color
coding or anything fancy, but before I went and confused
everyone I thought people might benefit from seeing a basic
script implemented as a user control.
The Code
Here's the code as it currently stands. It doesn't really
have any explanation or comments, but it's pretty straight-forward.
The first listing is for the control itself. There are a
couple things important to note here.
First off I'm using
databinding. You normally think of using it for datagrids
and the like, but you can use databinding to attach values
to almost anything in .NET. It tends to make for very simple
and straightforward looking pages. No messing with
assigning strings to properties of label objects...
just a simple layout with the values plugged in where
they go.
There is a slight downside... you need to call DataBind.
You could easily do this in the control, but I do have
a reason for not doing so.
I am planning to include quite a number of this type of
control on any given
page. Instead of calling the databind command at the
control level for each control... I'm going to do it
once at the page level and it will automatically
cascade down to every control on that page... pretty neat huh?
The second thing of interest here is the caching.
Reading off the file system can be an
expensive and time consuming operation when you start
talking about any real traffic. To combat this I
have the control set to output cache just like you
would do with a slow running ASP.NET page. The result
is that the control's output is saved in memory and
served directly without re-reading the contents of
the file. Give it a try... change one of the source
files once the control is cached... the control will
continue to output the old contents until the cache
expires.
srcview.ascx
<%@ OutputCache Duration="3600" VaryByParam="none" %>
<script language="VB" option="explicit" runat="server">
Public FileName As String
Function GetFileContents(FileName As String)
Dim objFile As System.IO.File
Dim objStreamReader As System.IO.StreamReader
objStreamReader = objFile.OpenText(Server.MapPath(FileName))
GetFileContents = Server.HTMLEncode(objStreamReader.ReadToEnd())
objStreamReader.Close()
End Function
</script>
<table cellspacing="0" cellpadding="0" border="1">
<caption><em><strong><%# FileName %></strong></em></caption>
<tr><td>
<pre>
<%# GetFileContents(FileName) %>
</pre>
</td></tr>
</table>
I couldn't very well stop there now could I? What good is
a control if you don't use it? Here's a simple page that
creates two instances of the control each passed it's own
value for the source of the file to read in.
Everything here is pretty basic... the only thing that
really needs mentioning is the Page.DataBind conmmand
in Page_Load. This is what I was talking about earlier.
By placing the command here it will trickle down to
all the controls on the page and will databind everything
at the same time.
default.aspx
<%@ Page Language="VB" %>
<%@ Register TagPrefix="asp101" TagName="SourceViewer"
Src="controls/srcview.ascx" %>
<script language="VB" option="explicit" runat="server">
Sub Page_Load(Src as Object, E as EventArgs)
Page.DataBind
End Sub
</script>
<html>
<head>
<title>ASP 101 - A Simple Text File Reading User Control</title>
</head>
<body>
<p>
Below are two instances of the user control.
The first reads in and displays the source of
this file, while the second does the same thing
for textfile.txt.
</p>
<asp101:SourceViewer runat="server" FileName="default.aspx" />
<asp101:SourceViewer runat="server" FileName="textfile.txt" />
</body>
</html>
As you can see it's pretty simple, but hopefully it'll
be helpful to someone. If you don't have a use for
the control itself, at least it might serve as a
simple example of databinding.
The more I work with .NET, the more I realize
that databinding is one of the most important concepts
in the .NET world.
Download
You can download a zip file containing the sample scripts
listed above from here: srcview.zip (1.6 KB).
