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 exists:

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;
}