The Obsolete attribute can be applied with or without a message argument. Marking something Obsolete without including advice on why it’s obsolete or what to use instead will lead maintainers to waste time trying to figure those things out.

Noncompliant Code Example

public class Car
{

  [Obsolete]  // Noncompliant
  public void CrankEngine(int turnsOfCrank)
  { ... }
}

Compliant Solution

public class Car
{

  [Obsolete("Replaced by the automatic starter")]
  public void CrankEngine(int turnsOfCrank)
  { ... }
}