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VBScript classes are a largely ignored aspect of ASP web development. This article will examine the power and flexibility of using classes inside an ASP page. Code: ASP 3.0 & VBScript


		Code Snippet

Code Written By: Scott Schluer from resume.icomdev.net

Using VBScript Classes To Encapsulate Common Database Functions
By Scott Schluer
Web/ASP Developer
sschluer@pacbell.net
http://resume.icomdev.net

VBScript classes are a largely ignored aspect of ASP web development. Most ASP developers learn linear coding techniques early in their training and never break from that habit. Although there are many ways to accomplish common development tasks (we'll examine ADO Data Access routines) this article's focus is on taking advantage of VBScript classes to create objects that we can use and reuse in all of our projects. Besides organizing applications into logical modules, increasing scalability and robustness, I was able to condense what would have been 61 lines of code within my ASP page down to 11 lines of readable code. This provides for dramatically better separation of function and presentation allowing for easier maintenance of the HTML code in the future.

We'll learn how to use VBScript classes to create objects that will perform ADO routines such as opening a connection and executing SQL select, insert, update and delete commands. The full code is available for download at the bottom of this page. That code includes error checking within the classes, however error checking is outside of the scope of this article and has not been included here. This article will, however, assume a basic knowledge of object-oriented programming and is intended to teach the reader a different way of accomplishing tasks that he/she uses in daily practice.

Let's examine the ADO class (I'll refer to it as our Database class). Create a file called ClassLib.inc. This is the file we'll use to save the code in, and will later be included via the include directive within our HTML page. ALL of our code will be encapsulated within the ASP delimiters (<% %>).  We will declare our class within VBScript like this:

<%
Class clsDB
End Class
%>

We now have a class called clsDB, which does absolutely nothing. The first chunk of code we want to place within our class declaration will handle opening a connection to a database. Let's look at the code:

Public Function OpenConn(strConnectString)
Set OpenConn = server.CreateObject("ADODB.Connection")
	OpenConn.CommandTimeout = 15
	OpenConn.ConnectionTimeout = 30
	OpenConn.Open strConnectString
End Function

As you probably noticed, it's not much different than the code you would usually use to open a connection. We create our function called OpenConn() with a parameter of strConnectString, which will be our connection string. The first line in the function creates an instance of the ADODB.Connection object. We then set various properties and open the database connection. The function call from our ASP page will look like this:

<--! #include file="ClassLib.inc" -->
Dim objDB
Set objDB = New clsDB
Set objDataBase = objDB.OpenConn("DRIVER={Microsoft Access Driver  (*.mdb)};DBQ=c:\db.mdb")

The code "<--! #include file="ClassLib.inc" -->" tells ASP to include the file that our class is stored in. "Set objDB = New clsDB" creates an instance of the class "clsDB" as an object. We can now call functions within our class using the format:

objDB.FunctionName(Parameter List)

After this code is executed, we can pass the objDataBase object as a parameter in our other function calls, effectively passing an open connection for our other functions to use. Now that we have a database connection established, let's use it. Our next function GetRecordset(), returns who would have guessed a recordset! Here's the code:

Public Function GetRecordset(strSelect, objConn, intCursorType, intLockType)
Set GetRecordset = Server.CreateObject("ADODB.Recordset")
	GetRecordset.Open strSelect, objConn, intCursorType, intLockType
End Function

This function is fairly straightforward. We create an instance of the ADODB.Recordset object and open it using parameters passed in our function call.  Notice the objConn parameter. This is where we pass our open database connection in order to retrieve our recordset. The function call would look like this, using our objDataBase connection object:

set rs = objDB.GetRecordset("SELECT * FROM tbl_test", objDataBase, 1, 1)

The first string in the parameter list is our strSelect parameter.  Followed by the open database connection (objConn) and the CursorType (intCursorType) and LockType (intLockType).  The last three methods that we will discuss are very similar in function.  We&#8217;ve examined how to open a database connection and retrieve a recordset.  Now let&#8217;s add, update and delete records using VBScript classes.

Public Sub AddRecord(strInsert, objConn) 
If (objConn.State) Then objConn.Execute(strInsert) 
End Sub

This is a simple example, however we could add functionality to it very easily.  My error-checking function is called from within my Subs like this:

Public Sub AddRecord(strInsert, objConn) 
On Error Resume Next 
If (objConn.State) Then objConn.Execute(strInsert) 
CheckError Err,"Error inserting record. Please contact administrator." 
End Sub

Our function call to add a record would look like this:

objDB.AddRecord "INSERT INTO table (field1) VALUES (value1)", objDataBase

You get an idea of how powerful these classes can be when you encapsulate a lot of your functionality inside a subroutine or a function.  Update and Delete are very similar.  Simply replace &#8220;strInsert&#8221; in the above example with &#8220;strUpdate&#8221;, or &#8220;strDelete&#8221; to indicate what your string is supposed to do and rename the sub to DeleteRecord or UpdateRecord.

So all of this looks pretty simple.  Where does the REAL power and flexibility come into play?  Good question.  After coding and debugging a VBScript class, you no longer have to code that functionality again in any of your projects.  It&#8217;s a reliable, bug-free, working class and you can use it again and again without worrying that it will crash on you.  I can&#8217;t stress enough that this is an incredible time-saver!


	CMS400.NET

To use the code above, click and drag your mouse over the code to highlight it. Then right click on the highlighted code and click "Copy." Now you may paste it into your code editor.

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