IUAVariable.VariableChange

This event occurs when the value of the project variable that the
IUAVariable
 C# object references changes.
event EventHandler<VariableChangeEventArgs> VariableChange;
IMPORTANT:
If the project variable refers to a field variable, the event is generated only if the project variable is kept synchronized with the field through a
RemoteVariableSynchronizer
 object, unless a link to the following entities already exists in
FactoryTalk Optix Studio
:
  • Tag variable from a graphical object
  • Data logger object
  • Alarm
  • Recipe schema object
In such a scenario, in a NetLogic, you can subscribe the change value method directly to the linked tag variable.

Event handler

The
VariableChange
 event handler enables you to subscribe a method to the event of the same name. 
public delegate void VariableChange(object sender, VariableChangeEventArgs e);

Event handler arguments

sender
 (object)
A C# object that corresponds to the object of the project origin of the event.
e
 (VariableChangeEventArgs)
A C# object that contains the following properties:
variable
 (IUAVariable)
The project variable that generated the event.
newValue
 (UAValue)
The new value of the variable.
oldValue
 (UAValue)
The previous value of the variable.
indexes
 (uint[])
Only for arrays:
 The indexes of the array cells in which the value has changed.
TIP: The property is empty if the value in each cell changes or if the project variable is scalar.

Example

The
Variable1_VariableChange
 method is executed each time the project variable
Variable1
 changes value. 
public override void Start()
{
    var variable1 = Project.Current.GetVariable("Model/Variable1");
    variable1.VariableChange += Variable1_VariableChange;
}

private void Variable1_VariableChange(object sender, VariableChangeEventArgs e)
{
    var label1 = Owner.Get<Label>("Label1");
    label1.Text = "Value of " + e.Variable.BrowseName + " changed from " + e.OldValue + " to " + e.NewValue;
}
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