Checks for a condition; if the condition is false, follows the escalation policy set by the analyzer and displays the specified message.
The default escalation policy is to notify the attached debugger about a contract failure or to display an Assert dialog box if a debugger is not attached. Optionally, the analyzer can be instructed to throw an exception. The userMessage parameter is passed to the debugger output. If userMessage is not a constant string literal, tools may not be able to read it.