C# Language Specification

Try-catch statements

For a statement stmt of the form:

try try-block

catch(...) catch-block-1
...
catch(...) catch-block-n

• 
  The definite assignment state of v at the beginning of try-block is the same as the definite assignment state of v at the beginning of stmt.
  
• 
  The definite assignment state of v at the beginning of catch-block-i (for any i) is the same as the definite assignment state of v at the beginning of stmt.
  
• 
  The definite assignment state of v at the end-point of stmt is definitely assigned if (and only if) v is definitely assigned at the end-point of try-block and every catch-block-i (for every i from 1 to n).
  

14. Try-finally statements

For a try statement stmt of the form:

try try-block finally finally-block

• 
  The definite assignment state of v at the beginning of try-block is the same as the definite assignment state of v at the beginning of stmt.
  
• 
  The definite assignment state of v at the beginning of finally-block is the same as the definite assignment state of v at the beginning of stmt.
  
• 
  The definite assignment state of v at the end-point of stmt is definitely assigned if (and only if) at least one of the following is true:
  

• 
  v is definitely assigned at the end-point of try-block
  
• 
  v is definitely assigned at the end-point of finally-block
  

If a control flow transfer (for example, a goto statement) is made that begins within try-block, and ends outside of try-block, then v is also considered definitely assigned on that control flow transfer if v is definitely assigned at the end-point of finally-block. (This is not an only if—if v is definitely assigned for another reason on this control flow transfer, then it is still considered definitely assigned.)

15.