| Article description
Microsoft has done an outstanding
job documenting the .NET Framework and providing a wealth of
examples. The majority of all the examples provided will show a
developer in detail how to utilize the Framework or concept in
question, that is if you're a VB or C# programmer! What about
NetCOBOL? Well Fujitsu Software is working on creating samples and
making them accessible to the general public. In the meantime
however, what's a COBOL developer supposed to do to solve a problem
you currently have? In this
article we'll take a look at some C# samples of code and then
translate those samples into COBOL. This article is intended to be
used as a model for you to follow when you run into a C# example and
need to convert it to COBOL. A really
neat trick! One of the
brightest people I know of has assisted Fujitsu Software in creating a
dual set of CD's titled "Microsoft .NET for COBOL Programmers". (This
set of CD's is currently available from Fujitsu Software). The author
of the CD's is Howard Hinman, President and CEO of Hinman Consulting.
Howard had a very good suggestion that I used while learning the .NET
environment, create a duplicate project in either VB.NET or C#. During
your development phase, create an additional project in your solution
using either of Microsoft's languages. Howard is more comfortable with
VB so he chose VB.NET, I am more comfortable with C# so I use it.
What we both do however is create an
additional project in our COBOL solution. If I am creating a WinForm
application then I create another WinForm application in C#. As I am
going through the COBOL development process if I have any questions on
how a specific namespace is implemented I use the other language
project to help me out. Now don't worry if you don't know C# at this
point. You will only be using it to try and help determine what a
certain objects method and properties are. In C# (and VB.NET) a
feature called 'intellisense' has been implemented. Intellisense
provides a programmer with additional information about an object when
they are using that object. We'll get to more of this in a little bit.
Syntactical Differences
C# uses an OBJECT-DOT-PROPERTY syntax. The
object in question may be a WinForm, a text box or any of the over
5,000 namespaces within the Framework. The key is when a developer
presses the dot (.) . When the dot is pressed a context sensitive window appears showing the
developer what options are available for that particular object. The
window may contain other objects, properties or methods that are
accessible to the object. Instead of remembering where a specific
property or method is within an object, by using intellisense a
developer can 'drill down' to the property or method they are looking
for. For instance, the
following code shows intellisense for a command button object.
VS.NET is waiting for the developer to
select an item or begin typing. When a developer begins typing
intellisense will position the list based on the input. So instead of
keying say 'Text', the developer would begin keying in 'T' and
intellisense will move the list to show all items beginning with 'T'.
Notice also the presence of tool-tip
text to inform the developer of what they are selecting. We are going
to modify the text on the face of the command button to be "Call
COBOL". To do this we need to select the 'text' property and set it to
"Call COBOL". The following image details the code necessary to
accomplish this. (We are interested in converting the code to COBOL so
we will complete the C# code for you to compare).
COBOL utilizes a different syntax to
call a method of an object or update it's properties. The syntax used
to set a property to value is SET PROP-WHATEVER OF OBJECT
TO SOMETHING.
The syntax used to invoke a method is
INVOKE OBJECT "METHOD"
USING (any parameters)
RETURNING (any parameters).
The items in blue
are required and are case sensitive. But what if the property or
method you are looking for is contained within another object
referenced by the current object? Simple, add another 'OF OBJECT'
phrase to the statement. We'll assume you are going to update a
property of an object that is called from another object. The syntax
would be similar to:
SET
PROP-WHATEVER OF OBJECT1
OF OBJECT2 TO
SOMETHING. Now
let's convert our sample.
Conversion
Following the guidelines detailed in the
preceding section, to update a button text in COBOL we would code the
following:
SET PROP-TEXT OF
button1 TO "CALL COBOL".
The completed method is:
Notice the use of the field PROP-TEXT.
PROP-TEXT is a pseudonym for the actual 'Text' property value for the
control.
This is defined in
the repository of the class and has the following syntax:
In COBOL, we use
the AS clause to create aliases for names that cannot otherwise be
written in COBOL. In other words, you create a name friendly to COBOL
and put the external name that might not be so COBOL friendly in
quotes after AS.
Wrap-Up
While the sample
presented is a simple one, the theory behind it flows through to all
of the NetCOBOL for .NET environment. Research what you are attempting
to accomplish. Locate the objects, property and method you are
attempting to use and then create either a C# or VB.NET project, if
possible. Create the programming necessary to do what you are
attempting and see how it is done in C# if no other sample are
available. Next, copy the line of code into your COBOL project
(commenting it out of course) and then following the above guidelines,
translate it into COBOL. Over time this process will become second
nature to you and soon you'll be coding native .NET calls without
doing the research. Remember, one has to learn to crawl before you can
run a marathon!
Happy Coding! |
