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Issues with reflection parameters within VB.net

Posted on 2010-09-20
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Last Modified: 2013-12-12
I'm having problems attempting to pass parameters that are gathered from various sources (XML, Database, etc). I have created an object array of the necessary parameters but i keep getting this error when trying to call the invoke option.

Object reference not set to an instance of an object.

It tells me to create a new instance of the object. I'm getting confused as I've stared at these lines of code for way too long.

Dim _params As New Object

                _params = parse_instructions(instructions(current_process).Split(","))

                'Set up the reflection call
                Dim objClass As Comms = Current_IOUnit.Current_Port
                Dim method As MethodInfo = objClass.GetType().GetMethod(current_process)

                'Call the function and save the value
                Return method.Invoke(objClass, _params)

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Thanks
Ben
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Question by:lazypeople
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7 Comments
 
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Expert Comment

by:käµfm³d 👽
ID: 33717921
Which line causes the exception?
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Author Comment

by:lazypeople
ID: 33717953
line 10 when i try to pass the params
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Accepted Solution

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käµfm³d   👽 earned 500 total points
ID: 33718029
Set a breakpoint at line 10 and make sure that "method" is not null (nothing).
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Author Comment

by:lazypeople
ID: 33718087
method appears to be nothing what should it be filled with?

Thanks
Ben
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Assisted Solution

by:lazypeople
lazypeople earned 0 total points
ID: 33718134
Ignore me i've just seen what ive done i for got to cross reference the integer to the method name

thank you
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Expert Comment

by:käµfm³d 👽
ID: 33718161
I would say work backwards.

Since you got to line 10, that means line 7 succeeded. GetMethod(current_process) would have failed if GetType() had not returned a valid object, so the problem must lie with GetMethod. Try setting your breakpoint at line 7, then open the Immediate Window ( Ctrl-Alt-i ). Execute the following in the Immediate Window:

   ?objClass.GetType().GetMethod(current_process)

You will most likely see "Nothing". See if you can determine why GetMethod() is failing. It may be something to do with "current_process".
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LVL 75

Expert Comment

by:käµfm³d 👽
ID: 33718168
NP.  Glad you got it figured out  :)
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