Assign to interface array initializator compiles but why?

Question

Today I was thinking it would be neat to make anonymous object which is type of some interface, and I have seen on SO that I am not only one.

Before I started checki

Answer 1

Holder holder = new Holder { someInterface = { Property = 1 } };//<--Note you missed new keyword

Above line is equal to

Holder temp = new Holder();
temp.someInterface.Property = 1;
Holder holder = temp;// <--Here someInterface is null so you get null reference exception. 

This should be something like

Holder holder = new Holder { someInterface = new SomeClass(){ Property = 1 } };//<--Note the new keyword here

Note: Your code never introduced "Anonymous Type" It is an "Object Initializer".

When you use ObjectInitializer syntax with new keyword it means you're setting something, when you use ObjectInitializer syntax without new keyword it means you're reading something.