Thank you.

Does the code that is supposed to fill in the textbox actually run? Can you put a breakpoint there?

It might seem silly, but I am asking this because the after changing to ReadItem, the .ToString() actually never returns an empty string. The ReadItem return a DAVtq object (value/timestamp/quality) taht always has "something" in it.

Or, the ReadItem can throw an exception. Isn't it the case, and the exception is somehow swollen? Again, stepping through the code should show whether it has made it successfully past the line with ReadItem or not.

Regards

1) How do you know that the behavior is not correct? I.e. how do you know that the string variable in the server is not, in fact, empty?

2) What result do you get in Connectivity Explorer when you view the actual item, and not the "Item Value" property (see my previous post)

3) In order to rule out any errors that are hidden, can you replace ReadItemValue with just ReadItem in your code, temporarily?

Best regards

Regarding the picture from the Connectivity Explorer: In that picture, you are not actually displaying the value of the item. You are displaying the "Item Value" property of the item, which is a different thing. I know it might be confusing, but it is simply so. OPC Properties are not meant to be used for efficient access, and in fact they may not work like this with many servers, unless you are actually using the same item in the regular way.

So what you are showing in the Connectivity Explorer is different from what the code snippet does.

In order to do the same as the code in the Connectivity Explorer, you need to click on the "GVL" node in the left pane (the tree), and the select the "MyString" from the list in the right pane.

Best regards

Please elaborate on what it means "it does not work". An exception? What is the error message? Etc.

The simplest way to read an OPC item would be:
To the second argument: You will have to supply the so-called ProgID of the server. It should be in its documentation, or it is possible to figure it out by browsing (see below).

The third argument is known as ItemID in OPC world. Be careful as it is usually qualified in some way (the syntax is server dependent). So while it is possible the it is simply "MyVar", it is usually longer, e.g. "Device1.Block1.MyVar". Check with the server documentation, or use e.g. the COnnectivity Explorer tool that comes with QuickOPC to connect to the server and browse for the items; it will show the full Item IDs in the info pane below the node tree.

If your client is remote to the server, you are likely to encounter DCOM configuration issues. That's a huge area that cannot be described in one paragraph.

Best regards