c# 运营商'??' 并作为'

Question

I saw this code but i don't know order of operators in second line. What's result of second line?

Object obj = 1;

String s = obj as String?? "";

Answer 1

C# operator precedence table states that as (see "relational and type-testing" row) operator has higher precedence then null-coalescing operator ( ?? ), so your expression will result in empty string, cause obj as String will evaluate to null thus null-coalescing operator will return right-hand operand, ie "" .