The lock statement obtains the mutual-exclusion lock for a given object, executes a statement, and then releases the lock. lock-statement : lock(expression)embedded-statement The expression of a lock statement must denote a value of a reference-type. No implicit boxing conversion (13.1.5) is ever performed for the expression of a lock statement, and thus it is a compile-time error for the expression to denote a value of a value-type. A lock statement of the form where x is an expression of a reference-type, is precisely equivalent to except that x is only evaluated once. [Example: The System.Type object of a class can conveniently be used as the mutual-exclusion lock for static methods of the class. For example: end example]