copy an object or component in .NET (newbie)

Question

Guys can tell me how to copying an object or component in .NET. dim A as listview A = MyListView MyListView.clear() MyListView = A I do like this and in the reality fail to where is wrong? Regars Mr. TOLIL (Newbie in .NET)

bmulcahy-07 · Answer

I'm new to vb .net but i've used other OOP languages. Your problem probably lies in the fact that your attempt to copy the list view doesnt copy the actual listview you want it copies a reference to the listview that you want in memory. When you set A = MyListView you are basically creating another name for the same listview. This is called a 'pointer' in other languages. A and MyListView both 'point' to the same location in memory they both 'point' to the same listview so when you clear the listview you clear the location in memory leaving A and MyListView pointing to a listview that doesnt exist anymore. A = MyListView really means: ////////////////////////////////// //ListView Memory Address//<---------------------------A ///////////////////////////////// ................../.\................... ...................|.................... ...................|.................... ...................|.................... ............MyListView............ so if you clear the MyListView reference: ////////////////////////////// //Empty Spot In Memory//<---------------------------A ////////////////////////////// .............../.\............... ................|................ ................|................ ................|................ .........MyListView......... (Excuse the periods - the forum wont allow a lot of spaces) What your code really says: dim A as listview 'create a new listview reference A = MyListView 'point this reference to the same place as MyListView points MyListView.clear() 'clear the place that both names point to MyListView = A ' set empty reference to empty reference there should be a copy method available to you within the listview object - something like: dim A as listview 'create a new listview reference A = MyListView.copy() 'point this reference to a new copy of MyListView MyListView.clear() 'clear the place that both names point to MyListView = A 'point MyListView to the same place as A points I dont know if there is a copy method for listview - there may be a built in function like copy(object) as object: dim A as listview 'create a new listview reference A = copy(MyListView) 'point this reference to a new copy of MyListView MyListView.clear() 'clear the place that both names point to MyListView = A 'point MyListView to the same place as A points if you dig around a bit you'll find it

mr_tolil · Answer

I already do that : dim A as listview A = MyListView '-->this is my existing list view when i do this command : MyListView.clear() MyListView = A I can't get back my original existing list view.. why?

kovan · Answer

dim blah as ListView = 'some existing list view or dim blah as ListView blah = 'some existing listview