Modifying Information in an OPC DA server If you want to write a data value into a specific OPC item, call the WriteItemValue method, passing it the data value you want to write, and individual arguments for machine name, server class, ItemID, and an optional data type. NOTE: OPCData.NET users can pass in ServerDescriptor and DAItemDescriptor objects, as well.   For writing data values into multiple OPC items in an efficient manner, call the WriteMultipleItemValues method. OPCData-COM users can pass in an array of values in place of each WriteItemValue argument, or (if the value is the same for the whole operation, e.g. the machine name), a single value as with the WriteItemValue call. OPCData.NET users will pass it an array of DAItemValueArgument objects, each specifying the location of OPC item, and the value to be written. Some newer OPC servers allow a combination of value, timestamp, and quality (VTQ) be written into their items. If you need to do this, call WriteItem or WriteMultipleItems method. Modifying Information in an OPC A&E server If you want to acknowledge a condition in OPC Alarms and Events server, call the AcknowledgeCondition method. You pass in individual arguments for machine name, server class, fully qualified source name, condition name, and an active time and cookie corresponding to the transition of the condition you are acknowledging. Alternatively, you can pass in a ServerDescriptor in place of machine name and server class arguments. Optionally, you can pass in acknowledger ID (who is acknowledging the condition), and a comment string. View code samples here