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DataValue Structure

A data value.

Namespace:  Demo3D.PLC.Comms
Assembly:  PLC (in PLC.dll) Version: 15.0.2.11458
Syntax
C#
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public readonly struct DataValue

The DataValue type exposes the following members.

Properties
  NameDescription
Public propertyIsNull
True if the value is null.
Public propertyTypeCode
Type code.
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Methods
  NameDescription
Public methodStatic memberAffectedArea
Returns the affected area from a DataValue created using Create(Buffer, MemoryAddress, AddressArea).
Public methodStatic memberCreateContextProvider
Creates a new IDataContextProvider for demarshalling DataValues.
Public methodEquals
Determines whether the specified value equals the current value.
(Overrides ValueTypeEquals(Object).)
Public methodGetDataType
Returns the type of the value (or null if the value is null).
Public methodGetHashCode
Returns a hash code for the current value.
(Overrides ValueTypeGetHashCode.)
Public methodGetTime
Returns the time of the event that produced the value.
Public methodGetValue
Returns the the actual .Net value.
Public methodGetValueStruct
Returns the the actual .Net value.
Public methodPeekValue
Returns the actual .Net value if it's immediately available, otherwise the base .Net value for a delta.
Public methodPropagateUpdate
Determines whether an update from this value to the specified value should be allowed to propagate.
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Fields
  NameDescription
Public fieldStatic memberNull
The null value.
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Remarks

This class wraps up a data value that we pass upstream/downstream. In the simplest case it's just a wrapper around an int or a bool.

The real use of this class is to wrap up deltas, where the information passed is not just the value of the tag but also a description of which parts of the data have changed. A simple example is Memory which passes the memory buffer for a byte[] tag, but also includes information about which part of the tag memory area actually changed.

Data deltas for structures (which property or properties within the structure) or for arrays (which elements in the array) are handled with special classes that derive from DataValue. These classes need to be aware of the threading model and to ensure that events (such as PropertyChanged or CollectionChanged don't get raised in the server thread, but get delayed and raised at the appropriate time in the user/model thread.

See Also