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. View code samples here