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Retrieving Data from a PLC

Is anyone familiar with getting information from a PLC and placing it into a text file?
We use Automated Solutions OPC Server to receive information from a PLC.  We then use VB.NET code (OPC Client) to grab and manipulate the data from the OPC Server.  When new information is placed in the OPC Server a data change event occurs.  However, the VB.NET code does not recognize the change event.  
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jmarkh68
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jmarkh68
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Bob LearnedCommented:
It's been about 10 years since I worked with OPC (with VB6), and I certainly never worked with VB.NET, but I still have an interest.  I assume that you are talking about a COM OPC client that you generated a RCW (Runtime Callable Wrapper or Interop library) for, from a type library.  How are you subscribing to the data change event?  What is the version information for Automated Solutions OPC server?  Do they have an online reference manual that I could reference?
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jmarkh68Author Commented:
Yes, I believe it is COM OPC.  I did not see an online manual at Automated Solutions, but their software comes with the industry standard guide for 2.02 found at OPC Foundation http://www.opcfoundation.org/.  Am I allowed to upload it here?  Let me see if the programmer is able to answer the other questions.
Thank you.
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jmarkh68Author Commented:
I believe we are using version 4.xx. Could you tell me more about subscribing to the data change event?  Is that defined by settings in the OPC Server or the code?  I probably will not have a response from the programmer till Monday, is that okay?  I may turn the conversation over to her if needed.
Thanks again for you help.
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Bob LearnedCommented:
The usual approach to subscribing to a COM event, is to attach an event handler to the event, that is exposed through the wrapper.  
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jmarkh68Author Commented:
Thank you for your response.  I am passing the info to my manager.  He checks email on the weekend.
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