Creating objects by name approach in .NET / C#

[Rene]

We are moving from VB6 to C# and we like to know a good approach in .NET /
C# for this:

In VB6 we have some objects (classes) with the same interface, i.e. a to
control specific printers. Based on the configuration we load the correct
object that belongs to the attached printer (example code):

Dim obj as PrinterObject
Dim MyPrinter as String

MyPrinter = ReadPrinterFromDatabase ()
Set obj = CreateObject(MyPrinter)
obj.Print "Hello World"

IMO there are two ways:

a) Create different classes for each printer and create the class, but I
don't see a way how to do this (obj = new getPrinterClassName(); ???)
unless we use some Case or If Then code. Less flexible because adding
printers needs a modification in the code.
b) Create the object from a DLL by giving the DLL name (of .NET objects??)

I don't know if there are some '.net' ways to to this, in fact we wish to
add/install some DLL or object (with or without registering) without
terminating the application. Then we can change the configuration and the
new object is loaded when used.

Regards,

Rene

 

[Aravind C]

Hi Rene,

You may like to take a look at .NET Reflection for your requirements.
Refection allows you load classes dynamically by the name of the class type.
To get started, please take a look at Assembly.CreateInstance() or
Activator.CreateInstance().

Regards,
Aravind C

 

[rsarosh]

Have a XML file for your printer configuration, define in
that
<XML>
<Printer name ="HP Laserjet 1100" Assembly="HP1100.dll">
<xml>

and load the assembly on the run time using
reflection ... This way you added a layer for indirection
and adding new printer will not require recompile of your
whole code ..

Search MSDN for Activator to get the code to do the
reflection..

Sarosh

 

[Rene]

Thanks for you answer, I read something about reflection not knowing it can
be used for this.

Rene