Why can the c# compiler not resolve the argument types of a lambda expression in a ternary operator?

Question

I have this code:

Action<A, B> fnUpdate = (someBool) ? (a, b) => a.propOne = b : (a, b) => a.propTwo = d;

Why can the compiler not resolve the types of a and b, just because it is assigned in a ternary operator? it seems quite straight forward at face value.

try to add brackets over the functions - its somewhat ambiguous. — Mark Segal, May 17 '13 at 08:23

score 1 · Accepted Answer · answered May 17 '13 at 08:28

The C# compiler tries to create the lambdas independently and cannot unambiguously determine the type. Hence cast it to work as expected....

Action<A, B> fnUpdate = (someBool) 
                       ? (Action<A, B> (a, b) => a.propOne = b 
                       : (Action<A, B> (a, b) => a.propTwo = d);

score 0 · Answer 2 · answered May 17 '13 at 08:29

0

You need to cast at least one of the two functions:

Action<A, B> fnUpdate = someBool
   ? (Action<A, B>)((a, b) => a.propOne = b)
   : (a, b) => a.propTwo = b;

answered May 17 '13 at 08:29

Dave Cousineau

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Why can the c# compiler not resolve the argument types of a lambda expression in a ternary operator?

2 Answers2