Suppose the C# source contains:
team1.DisplayName();
A sequence diagram can represent that call as a message sent to team1.
Conceptually:
caller ── DisplayName() ──> team1
The arrow shows the direction of the call.
The label names the method being called.
For:
team1.DisplayName();
the receiver is:
team1
For:
player1.ShowStatus();
the receiver is:
player1
The sequence diagram should send the message to the object whose method executes.
If the method is:
DisplayName()
do not label the diagram message:
ShowTeam()
unless the source and model actually use that name.
Consistency helps you trace UML to code.
If code performs:
team1.ResetScore();
team1.DisplayName();
the first message belongs above the second message in the sequence diagram.
The diagram models execution order.
Method parameters are taught later.
At this boundary, a simple message such as:
DisplayName()
is enough to represent a parameterless method call.
The lifelines represent participants.
The messages represent communication between them.
Do not replace each method call with an activity-diagram action box.
Choose notation that matches the interaction question.