C# Language Specification

Foreach statements

For a foreach statement stmt of the form:

foreach ( type identifier in expr ) embedded-statement

• 
  The definite assignment state of v at the beginning of expr is the same as the state of v at the beginning of stmt.
  
• 
  The definite assignment state of v on the control flow transfer to embedded-statement or to the end point of stmt is the same as the state of v at the end of expr.
  

17. Using statements

For a using statement stmt of the form:

using ( resource-acquisition ) embedded-statement

• 
  The definite assignment state of v at the beginning of resource-acquisition is the same as the state of v at the beginning of stmt.
  
• 
  The definite assignment state of v on the control flow transfer to embedded-statement is the same as the state of v at the end of resource-acquisition.
  

18. Lock statements

For a lock statement stmt of the form:

lock ( expr ) embedded-statement

• 
  The definite assignment state of v at the beginning of expr is the same as the state of v at the beginning of stmt.
  
• 
  The definite assignment state of v on the control flow transfer to embedded-statement is the same as the state of v at the end of expr.
  

19. Yield statements

For a yield return statement stmt of the form:

yield return expr ;

• 
  The definite assignment state of v at the beginning of expr is the same as the state of v at the beginning of stmt.
  
• 
  The definite assignment state of v at the end of stmt is the same as the state of v at the end of expr.
  

A yield break statement has no effect on the definite assignment state.

20. General rules for simple expressions

The following rule applies to these kinds of expressions: literals (§7.6.1), simple names (§7.6.2), member access expressions (§7.6.4), non-indexed base access expressions (§7.6.8), typeof expressions (§7.6.11), and default value expressions (§7.6.13).

• 
  The definite assignment state of v at the end of such an expression is the same as the definite assignment state of v at the beginning of the expression.
  

21.