Create object through classname

  • Thread starter Thread starter Bert
  • Start date Start date
B

Bert

Hi,

I want to create an instance of a class by means of the classname. Can't figure out how.

in pseudocode this would look like:

Dim MyClassName as String = "MyClass"
Dim MyObject as New MyClasses(MyClassName)

Thanks for your help,

Egbert
 
Bert said:
Hi,

I want to create an instance of a class by means of the classname.
Can't figure out how.

in pseudocode this would look like:

Dim MyClassName as String = "MyClass"
Dim MyObject as New MyClasses(MyClassName)
Click to expand...


I wonder why people need the class name at runtime, but if it's necessary,
have a look at System.Activator.CreateInstance


Armin
 
Egbert,

Do you have a goal with this thousand times by newbies asked questions who
want to convert VBA functions to VBNet?

Be aware that VBNet does beside using it for giving debugging informations
nothing with Object names, it is just for you to make it readable.

Cor
 
Hi Egbert,

As Armin has said, you can use the System.Activator.CreateInstance methods
to create an instance, but be aware that this pseudo-code:

Dim MyClassName as String = "MyClass"
Dim MyObject as New MyClasses(MyClassName)

is not very robust. If the name of the type "MyClass" changes and you don´t
update that string, your code will fail at run-time. A more common approach
is to create the instance from the type:
System.Activator.CreateInstance(type), and you can get the type through
several ways. For example, you can get the types of an assembly with
Assembly.GetTypes, or only the public types with Assembly.GetExportedTypes.
You can examine some properties (the bases or implemented interfaces) of the
type to guess which ones you want to create instances from. This is quite
common when creating plug-in frameworks.

Bottom line: if you know what you are doing, OK, but if not you can think
about the above.

--

Best regards,

Carlos J. Quintero

MZ-Tools: Productivity add-ins for Visual Studio
You can code, design and document much faster:
http://www.mztools.com


"Bert" <[email protected]> escribió en el mensaje
Hi,

I want to create an instance of a class by means of the classname. Can't
figure out how.

in pseudocode this would look like:

Dim MyClassName as String = "MyClass"
Dim MyObject as New MyClasses(MyClassName)

Thanks for your help,

Egbert
 
Thanks Armin, Carlos and Cor,

I do have a goal with this question, I'm using a form that uses objects from different classes, depending on user's input. So in order to create the objects I need this code:

Function CreateObject("ClassName" as String) as Object
dim oType as Type = Type.GetType("ClassName")
Return Activator.CreateInstance(oType)
End Function

No worries about changing names, since everything is decribed and maintained in the databases.

Egbert
 
Bert said:
Thanks Armin, Carlos and Cor,

I do have a goal with this question, I'm using a form that uses
objects from different classes, depending on user's input. So in
order to create the objects I need this code:

Function CreateObject("ClassName" as String) as Object
dim oType as Type = Type.GetType("ClassName")
Return Activator.CreateInstance(oType)
End Function

No worries about changing names, since everything is decribed and
maintained in the databases.
Click to expand...


After creating the object, do you intend to use the members inherited
from System.Object only?


Armin
 
Bert said:
No, I use the members by means of Reflection.
Click to expand...


I see. I asked only because otherwise I would have suggested a common
interface or base class.


Armin
 
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