ECMA-334: 12.3.3.26 ?: expressions

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C# Language Specification

12. Variables 12.3 Definite assignment 12.3.3 Precise rules for determining definite assignment 12.3.3.1 General rules for statements 12.3.3.2 Block statements, checked, and unchecked statements 12.3.3.3 Expression statements 12.3.3.4 Declaration statements 12.3.3.5 If statements 12.3.3.6 Switch statements 12.3.3.7 While statements 12.3.3.8 Do statements 12.3.3.9 For statements 12.3.3.10 Break, continue, and goto statements 12.3.3.11 Throw statements 12.3.3.12 Return statements 12.3.3.13 Try-catch statements 12.3.3.14 Try-finally statements 12.3.3.15 Try-catch-finally statements 12.3.3.16 Foreach statements 12.3.3.17 Using statements 12.3.3.18 Lock statements 12.3.3.19 General rules for simple expressions 12.3.3.20 General rules for expressions with embedded expressions 12.3.3.21 Invocation expressions and object creation expressions 12.3.3.22 Simple assignment expressions 12.3.3.23 && expressions 12.3.3.24 || expressions 12.3.3.25 ! expressions 12.3.3.26 ?: expressions 12.3.3.27 Anonymous method expressions 12.3.3.28 Yield statements 12.3.3.29 ?? expressions

© 2006 ECMA International

12.3.3.26 ?: expressions

For an expression expr of the form expr-cond ? expr-true : expr-false:

• The definite assignment state of v before expr-cond is the same as the state of v before expr.

• The definite assignment state of v before expr-true is definitely assigned if and only if the state of v after expr-cond is definitely assigned or "definitely assigned after true expression".

• The definite assignment state of v before expr-false is definitely assigned if and only if the state of v after expr-cond is definitely assigned or "definitely assigned after false expression".

• The definite assignment state of v after expr is determined by:

• If expr-cond is a constant expression (§14.16) with value true then the state of v after expr is the same as the state of v after expr-true.

• Otherwise, if expr-cond is a constant expression (§14.16) with value false then the state of v after expr is the same as the state of v after expr-false.

• Otherwise, if the state of v after expr-true is definitely assigned and the state of v after expr-false is definitely assigned, then the state of v after expr is definitely assigned.

• Otherwise, the state of v after expr is not definitely assigned.