ReadItemValue Method (IEasyDAClientExtension)

Reads a named item from an OPC server. Only the item value is returned (quality and timestamp are not returned).

The server 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.

Use this method if you are only interested in the actual value of the OPC item. Use ReadItem method if you also need the quality or timestamp. The ReadItemValue method makes it very easy to obtain the actual data value with just one function call.

The ReadItemValue method waits until the quality becomes "good", or the timeout elapses.

Overload List

Overload	Description
ReadItemValue(IEasyDAClient,DAItemArguments,DAReadParameters)	Reads a named item from an OPC server. Only the item value is returned (quality and timestamp are not returned). Reads a value of a named item using an item arguments objects, and read parameters.
ReadItemValue(IEasyDAClient,DAReadItemArguments)	Reads a named item from an OPC server. Only the item value is returned (quality and timestamp are not returned). Reads a value of a named item using an object that holds all necessary arguments.
ReadItemValue(IEasyDAClient,ServerDescriptor,DAItemDescriptor)	Reads a named item from an OPC server. Only the item value is returned (quality and timestamp are not returned). Reads a value of named item using descriptor objects for the OPC server and OPC-DA item.
ReadItemValue(IEasyDAClient,ServerDescriptor,DAItemDescriptor,DAReadParameters)	Reads a named item from an OPC server. Only the item value is returned (quality and timestamp are not returned). Reads a value of named item using descriptor objects for the OPC server and OPC-DA item, and specifying read parameters such as the data source or value age..
ReadItemValue(IEasyDAClient,String,String,String,VarType)	Reads a named item from an OPC server. Only the item value is returned (quality and timestamp are not returned). Reads a value of named item using individual parameters specifying its location, and a specific data type.
ReadItemValue(IEasyDAClient,String,String,String,VarType,Int32)	Reads a named item from an OPC server. Only the item value is returned (quality and timestamp are not returned). Reads a value of named item using individual parameters specifying its location, a specific data type, and value age.
ReadItemValue(IEasyDAClient,String,String,String)	Reads a named item from an OPC server. Only the item value is returned (quality and timestamp are not returned). Reads a value of named item using individual parameters specifying its location, using server's canonical data type.

Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2012, Windows Server 2016; .NET Core, .NET 5, .NET 6: Linux, macOS, Microsoft Windows

Reference

IEasyDAClientExtension Class
IEasyDAClientExtension Members