Struct initialization and new operator

Question

I have two similar structs in C#, each one holds an integer, but the latter has get/set accessors implemented.

Why do I have to initialize the Y struct with

Answer 1

This is covered in the C# specification section 5.3 dealing with "Definite Assignment":

a struct-type variable is considered definitely assigned if each of its instance variables is considered definitely assigned.

and:

An initially unassigned variable (Section 5.3.2) is considered definitely assigned at a given location if all possible execution paths leading to that location contain at least one of the following:
* A simple assignment (Section 7.13.1) in which the variable is the left operand.
* ...

As such, this also works:

void Main()
{
    X x;
    x.a = 1;
    x.b = 2;

    x.Dump();
}

public struct X
{
    public int a;
    public int b;
}

You can test this in LINQPad.

Note that there is no way for the compiler to prove that the struct-type variable is considered definitely assigned if you call code on it, and that's what you're doing with a property. As such, before you can use a property on the struct-type variable, it has to be definitely assigned.