Create a subscription

You create a subscription inside the
Start()
 method.
TIP:
To insert a new method automatically:
  • In Visual Studio, place the caret after the
    +=
     operator, and press
    twice.
  • In Visual Studio Code, refer to the editor suggestions.

Example

In this example, the
Session_UserChange
 method is subscribed to the user change event using the
UserChange
 event handler and the
+=
 operator. 
public override void Start()
{
    Session.UserChange += Session_UserChange;
}
IMPORTANT: Always cancel the subscription in the
Stop()
 method to avoid a memory leak. See Cancel a subscription.
The following example shows the
Session_UserChange
 method. 
private void Session_UserChange(object sender, UserChangeEventArgs e)
{
    Log.Info(e.newUser.BrowseName);
}
sender
The
IUAObject
 object that corresponds to the node origin of the event.
e
The C# object that contains the event data based on the data type of the event handler (
UserChangeEventArgs
 in the example).

Event handlers

Depending on the event type, create a subscription by using different event handlers.
Value change of a variable event
To subscribe a method to the value change of a variable, use the
VariableChange
 event handler, supplied by the
IUAVariable
 class. See IUAVariable.VariableChange.
All events generated by an object
To subscribe a method to all events generated by an object, use the
UAEvent
 event handler, supplied by the
IUAObject
 class. See IUAObject.UAEvent.
A specific event of an object
To subscribe a method to a specific event generated by an object, use the corresponding event handler supplied by the type.
In this example, the
OnMouseClick
 event handler runs the
Button2_OnMouseClick
 method each time
Button2
 is pressed. The
OnMouseClick
 event handler is supplied by the
Button
 class. 
public override void Start()
{
    var button2 = Owner.Get<Button>("Button2");
    button2.OnMouseClick += Button2_OnMouseClick;
}

private void Button2_OnMouseClick(object sender, MouseClickEvent e)
{
    var label2 = Owner.Get<Label>("Label2");
    var button = (Button)sender;
    label2.Text = "Mouse click event on " + button.BrowseName;
}
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