QuickOPC User's Guide and Reference
ReadMultipleItemValues Method (IEasyDAClientExtension)



OpcLabs.EasyOpcClassicCore Assembly > OpcLabs.EasyOpc.DataAccess Namespace > IEasyDAClientExtension Class : ReadMultipleItemValues Method
Reads named items from an OPC server or OPC servers. Only the item values are returned (qualities and timestamps are not returned).

The servers can be local or can be remotely accessed via DCOM. Optionally, an access path can be specified or a specific data type can be requested.

The ReadMultipleItemValues method requires that the quality is "good" for each item. The function performs all individual operations in parallel, but only returns after all individual operations are completed (or their timeouts elapse).

This method does not throw an exception in case of OPC operation failures. Instead, the eventual exception related to each item is returned in Exception property of each returned OpcLabs.EasyOpc.DataAccess.OperationModel.DAVtqResult element.

Overload List
OverloadDescription
Reads named items from an OPC server or OPC servers. Only the item values are returned (qualities and timestamps are not returned). Reads multiple named item values, using item arguments objects, and common read parameters.  
Reads named items from an OPC server or OPC servers. Only the item values are returned (qualities and timestamps are not returned). Reads multiple named item values from a single OPC server, using array of argument objects as an input.  
Reads named items from an OPC server or OPC servers. Only the item values are returned (qualities and timestamps are not returned). Reads multiple named item values from a single OPC server, using descriptor objects for the OPC server and OPC-DA items.  
Reads named items from an OPC server or OPC servers. Only the item values are returned (qualities and timestamps are not returned). Reads multiple named item values from a single OPC server, using descriptor objects for the OPC server and OPC-DA items, and specifying read operation parameters.  
Remarks

 

This is a multiple-operation method. In a properly written program, it does not throw any exceptions. You should therefore not put try/catch statements or similar constructs around calls to this method. The only exceptions thrown by this method are for usage errors, i.e. when your code violates the usage contract of the method, such as passing in invalid arguments or calling the method when the state of the object does not allow it. Any operation-related errors (i.e. errors that depend on external conditions that your code cannot reliably check) are indicated in the result objects returned by the method. For more information, see Multiple-operation Methods and Do not catch any exceptions with asynchronous or multiple-operation methods.
Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows

See Also