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Loading a class from a string with a class name.

I don't no if this is easy to do?

I would like to make a function like

FillCombo(ddControl, CollectionClass, ValueField, TextField, NeedsNullValueRow)

this is the code that works:

            Dim BuyerCol As New Csb.EabOrder.EabOrderBuyerCollection
            BuyerCol.LoadAll()
            Dim buyer As Csb.EabOrder.EabOrderBuyer
           
            dropdown.Items.Clear()
            Dim FirstlistItem As New ListItem("", "")
            dropdown.Items.Add(FirstlistItem)
           
            For Each Buyer In BuyerCol
                Dim listItem As New ListItem(Buyer.BuyerName, Buyer.BuyerId)
                dropdown.Items.Add(listItem)
            Next

Thanks.
0
keezebees
Asked:
keezebees
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1 Solution
 
Mohamed ZedanCommented:
I don't get what you want ?
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keezebeesAuthor Commented:
Sorry, should be al little more specific.

What i want is an function that automates the listed code
To do that I would have to be able to make an instance of the some classes just by there class name (string)
And thats what my problem is.

How do ik load the class 'Csb.EabOrder.EabOrderBuyer' as an instance based on only a class name??

public Function FillCombo(ddControl as dropdownlist, CollectionClassName as string, ValueField as string, TextField as string, NeedsNullValueRow as boolean) as boolean

Hope this is more clear.
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Mohamed ZedanCommented:
ok to create an instance just by classname is like this

        Dim asm As Reflection.Assembly = Reflection.Assembly.GetExecutingAssembly
        Dim instance As Object = asm.CreateInstance(CollectionClassName)

if the collection class implements Ienumerable you should be able to enumerate through its items

just like
              for each buyer in buyercol

will be replaced by

             dim Enumer as iEnumrator = ctype(instance,IEnumerable).getEnumerator
             while enumer.movenext
                 dim buyer as object = enumer.current
                 'Work with the buyer object
             end while

If you need more info please ask :) ...
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keezebeesAuthor Commented:
Thanks mohzedan.

Any Idea why i get an 'object reference not set to an instance of an object' error??

NullReference exception was unhandled by user code


Private Sub test()
            Dim asm As System.Reflection.Assembly = System.Reflection.Assembly.GetExecutingAssembly
            Dim instance As Object = asm.CreateInstance("csb.EabOrder.EabOrderVerkoopOrderViewCollection")

'object reference error is here!!!!!            
Dim Enumer As IEnumerator = CType(instance, IEnumerable).GetEnumerator
            While Enumer.movenext
                Dim buyer As Object = Enumer.Current
                'Work with the buyer object
            End While

        End Sub
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Mohamed ZedanCommented:
try using eaborderverkooporderviewCollection
only in the createinstance...
and could you run this code
after dim asm .....

Dim types As Type() = asm.GetTypes
for i as integer = 0 to asm.length-1
  Console.writeline(asm(i).Name)
next

and the names of the types that are printed are the names you could load using this way.
i.e. asm.createinstance("name of type from the list printed")
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Mohamed ZedanCommented:
the exception is because the type name wasn't found in that assembly ... if it is contained in  a dll then that dll should be loaded ... if that type is in your namespace just check it's type name correctly ...
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keezebeesAuthor Commented:
ehh...

asm.length doesnt excists....

Must be getting to late for me:)
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Mohamed ZedanCommented:
sorry i meant types.length must be too late for me too . :)
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keezebeesAuthor Commented:
Like this right?

Dim asm As System.Reflection.Assembly = System.Reflection.Assembly.GetExecutingAssembly
            Dim instance As Object = asm.CreateInstance("Csb.EabOrder.EabOrderVerkoopOrder")

            Dim types As Type() = asm.GetTypes
            For i As Integer = 0 To types.Length - 1
                MsgBox(types(i).Name)
            Next
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Mohamed ZedanCommented:
yes but instead of the msgbox use console.writeline(types(i).name)

that way you'll have them written in the output window
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keezebeesAuthor Commented:
Here is the output:

MyComputer
MyProject
ThreadSafeObjectProvider`1
desktopmodules_csb_eaborder_editcsb_eaborder_ascx
EditCsb_EabOrder
desktopmodules_csb_eaborder_viewcsb_eaborder_ascx
ViewCsb_EabOrder
desktopmodules_csb_eaborder_settings_ascx
Settings
FastObjectFactory_app_web_yu75jgso
MyComputer
MyProject
ThreadSafeObjectProvider`1
desktopmodules_csb_eaborder_editcsb_eaborder_ascx
EditCsb_EabOrder
desktopmodules_csb_eaborder_viewcsb_eaborder_ascx
ViewCsb_EabOrder
desktopmodules_csb_eaborder_settings_ascx
Settings
FastObjectFactory_app_web_yu75jgso
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keezebeesAuthor Commented:
Sorry  mohzedan,

Have to go now.
Will be back for another go tomorrow.

Thanks.
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Mohamed ZedanCommented:
see you tomorrow :)
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keezebeesAuthor Commented:
A bit late, but here are your points.
Just got it to work

Thanks.
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Mohamed ZedanCommented:
Sorry for being too late :)
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Mohamed ZedanCommented:
If you need any more info post here ok ... :)
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keezebeesAuthor Commented:
well,

what i did was just write my code the way i would normaly do.
Do the testing making sure that I dont need to come back no more.
And then i replaced my object declaration with:

Dim instance As Object = asm.CreateInstance(CollectionClassName)

intellisence obviusly wont work, but hey, who needs intellisence.........well actuali I do but dont tell anyone Ok?

can you tell me a bit more about  supporting Ienumerable in a class so i could do the enumerating?
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Mohamed ZedanCommented:
What is your collection class like ?
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keezebeesAuthor Commented:
I am using EntitySpaces for my DAL

You  know of that??
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Mohamed ZedanCommented:
I just read about it .... your collections should already implement Ienumerable
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