Create an object whose type is in a string paramet

问题:

I have a TreeView, which contains nodes. When a user clicks on a node, corresponding CrystalReport document should be created and displayed.

For example, names of my nodes are: "PeriodReport1", "PeriodReport2", "PeriodReport3". My CrystalReport documents are named same: "PeriodReport1", "PeriodReport2", "PeriodReport3".

How can I create and display right type of crystal reports document? I could do something like this:

select case reportName
    case "PeriodReport1"
        dim myReport as new PeriodReport1
    case "PeriodReport2"
        dim myReport as new PeriodReport2
    ...
end select

But probably there is a nicer way to do this. Can I use reflection to do this?

回答1:

As long as the reports have a default paramaterless constructor, i.e. you can say new PeriodReport...

Activator.CreateInstance(Type.GetType("namespace.typename"))

回答2:

Something like this:

Type t = Type.GetType("object type name");
TBaseObj new_obj = (TBaseObj) Activator.CreateInstance(t);

回答3:

You can also stash an object of any type in the tag property of the TreeNode, which is often useful for this sort of thing. It's not very MVC, but can be a good fit if you're not already trying to keep models and views separate (which WinForms doesn't encourage you to do)

回答4:

What about casting? How do I cast a 'Object' instance? Something like

string myCustomClassName = getMyCustomClassName();
var myCustomInstance = (???????)myGenericObject; //What do I replace ?????? with?