Slapping Together a Photo Gallery in ASP.NET Part II - Two Sides of a Coin
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In the previous article, I introduced two similar objects to manage folders on the .NET platform - the Directory() and DirectoryInfo() objects. So, it should not come as a surprise to learn that a similar duality exists for managing files on the server.
It's time to say hello to the FileInfo() object, a counterpart of the DirectoryInfo() object, introduced earlier. Take a peek at the next code listing that introduces this new object and a whole lot more:
<%@ Page Language="C#" Debug="true" %>
<%@ Import Namespace="System.IO" %>
<SCRIPT language="C#" runat="server">
// custom function to return the list of photographs
// a.k.a. image files for a particular file system location
void GetPhotos(string strFileSystemPath) {
// define array to store list of "Photos"
FileInfo[] objPhotos;
try {
// instantiate a DirectoryInfo() object
DirectoryInfo objCurrentAlbum = new DirectoryInfo
(strFileSystemPath);
// use the GetFiles() method
// to obtain a list of photos i.e. image files
objPhotos = objCurrentAlbum.GetFiles("*.jpg");
if(objPhotos.Length != 0) {
// there are photos in the current album
// enable the photo display panel
pnlPhotos.Visible = true;
foreach(FileInfo objPhoto in objPhotos) {
// check if the photo i.e. image file exists
if(objPhoto.Exists) {
// if it does, add a Image() object
// to Photo Panel
Image objImage = new Image();
objImage.ImageUrl = objPhoto.FullName.Substring
(Request.PhysicalApplicationPath.Length) ;
objImage.Width = 200;
objImage.Height = 145;
pchPhotos.Controls.Add(objImage);
pchPhotos.Controls.Add(new LiteralControl("<HR
width=\"25%\" align=\"left\">"));
}
}
} else {
error.Text = "Sorry, there are no photographs in
the current Photo Album.";
}
} catch (Exception e) {
error.Text = "An exception occurred: " + e.Message;
}
}
void Page_Load(Object sender, EventArgs e) {
// path to a particular Photo Album
// i.e. folder on the file system
string strPhotoAlbumPath = "E:\\inetpub\\wwwroot\\Gallery\\London";
// display name of current Photo Album
int intStartPosition = strPhotoAlbumPath.LastIndexOf("\\") + 1;
int intLength = strPhotoAlbumPath.Length -
intStartPosition;
output.Text += "You are currently viewing the <U>"
+ strPhotoAlbumPath.Substring(intStartPosition,
intLength) + "</U> Photo Album.";
// check if the specified Photo Album i.e. folder exists
if(Directory.Exists(strPhotoAlbumPath)) {
// get the list of photos
// in a particular Photo Album
GetPhotos(strPhotoAlbumPath);
} else {
error.Text = "Sorry, the folder <U>" +
strPhotoAlbumPath + "</U> could not be located.";
}
}
</SCRIPT>
<HTML>
<HEAD>
<TITLE>My Gallery</TITLE>
<BASEFONT face="Arial" />
</HEAD>
<BODY>
<!-- Panel for Photos -->
<asp:Panel id="pnlPhotos" visible="false" runat="server" >
<asp:Label id="output" runat="server" />
<BR /><BR />
<asp:Placeholder id="pchPhotos"
runat="server" />
</asp:Panel>
<!-- Error label -->
<asp:Label id="error" runat="server" visible="true"
style="color:#FF0000;"/>
</BODY>
</HTML>
Load the above example in your browser to view following output:
For the first time, I've updated the code listing to display the image files rather than just names, sizes and other useless information that I've been doing so far.
While the above example appears to be daunting at first glance, it is my job to de-mystify the complexities. Let’s do that by breaking the code listing into smaller bits. Concentrate on the HTML portion of the ASP.NET script. Here, you'll notice that I have introduced a couple of ASP.NET server controls: first, the "Panel" control allows you to group several .NET server controls together and next, the "Placeholder" control defines a placeholder to add new server controls at run-time.
The Page_Load() function has been excerpted from an example in the previous article. There are two important points to keep in mind. First, I've defined a string variable titled "strPhotoAlbumPath" to store the file system location of a selected "Photo Album." Second, I've obtained the name of the current "Photo Album," i.e. folder, using some deft string manipulation.
Next, I've revamped the ubiquitous GetPhotos() function: here, I've a defined an array titled "aryPhotos" to store a collection of FileInfo() objects, unlike the earlier example, where a similar array stored string values. Next, I've instantiated a DirectoryInfo() object and invoked its GetFiles() method. This returns a collection of FileInfo() objects that I store in the aforementioned "aryPhotos" array. Note that each object in this collection represents a "Photo," i.e. an image file.
As usual, the FileInfo() object exposes many properties that provide useful information about the file. You can view the entire list at the following URL: http://msdn.microsoft.com/library/en-us/cpref/html/frlrfSystemIOFileInfoClassTopic.asp
In the above example, I've obtained the absolute file system path by using the "FullName" property of the FileInfo() object and the "Request.PhysicalApplicationPath" property. I've calculated the path of every image file, relative to the root folder of the application. This comes in handy when I assign the URL for every Image() object that I've added to my "pchPhotos" placeholder server control.
The "LiteralControl" server control allows me to insert custom text (including HTML code) within the "pchPhotos" placeholder. I've used it to insert horizontal lines after each photograph, as seen in the output.
Note the use of "if-else" and "try-catch" blocks to trap errors if something goes wrong; it is a good practice to expect the unexpected.
Next: My Gallery >>
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