C# Language Specification

! expressions

For an expression expr of the form ! expr-operand:

• 
  The definite assignment state of v before expr-operand is the same as the definite assignment state of v before expr.
  
• 
  The definite assignment state of v after expr is determined by:
  

• 
  If the state of v after expr-operand is definitely assigned, then the state of v after expr is definitely assigned.
  
• 
  If the state of v after expr-operand is not definitely assigned, then the state of v after expr is not definitely assigned.
  
• 
  If the state of v after expr-operand is “definitely assigned after false expression”, then the state of v after expr is “definitely assigned after true expression”.
  
• 
  If the state of v after expr-operand is “definitely assigned after true expression”, then the state of v after expr is “definitely assigned after false expression”.
  

27. ?? expressions

For an expression expr of the form expr-first ?? expr-second:

• 
  The definite assignment state of v before expr-first is the same as the definite assignment state of v before expr.
  
• 
  The definite assignment state of v before expr-second is the same as the definite assignment state of v after expr-first.
  
• 
  The definite assignment statement of v after expr is determined by:
  

• 
  If expr-first is a constant expression (§7.19) with value null, then the the state of v after expr is the same as the state of v after expr-second.
  

• 
  Otherwise, the state of v after expr is the same as the definite assignment state of v after expr-first.
  

28.