OPC-DA item values (or OPC-UA node attributes) can be also read once, when the form or window loads.
How to configure this feature for OPC-DA:
On a PointBinder, edit the BindingGroups collection, "Add" a new binding group, set its AutoRead property to True, and make sure that its AutoSubscribe property is set to False.
On a TextBox (or other control), use "Bind to Point" command and select the OPC item you want to read. Then, use the "Edit Live Bindings" command, and set the BindingGroup property of the item binding to the binding group you have created earlier. The Read operation is automatically executed for all item bindings in this group when the form loads.
How to configure this feature for OPC-UA:
On a PointBinder, edit the BindingGroups collection, "Add" a new binding group, set its AutoRead property to True, and make sure that its AutoSubscribe property is set to False.
On a TextBox, use "Bind to Point" command and select the OPC-UA node you want to read. Then, use the "Edit Live Bindings" command, and set the BindingGroup property of the data binding to the binding group you have created earlier. The Read operation is automatically executed for all data bindings in this group when the form loads.