Can anyone explain this strange behavior with signed floats in C#?

Question

Here is the example with comments:

class Program
{
    // first version of structure
    public struct D1
    {
        public double d;
        public int f         


        

Answer 1

Simpler test case:

Console.WriteLine("Good: " + new Good().Equals(new Good { d = -.0 }));
Console.WriteLine("Bad: " + new Bad().Equals(new Bad { d = -.0 }));

public struct Good {
    public double d;
    public int f;
}

public struct Bad {
    public double d;
}

EDIT: The bug also happens with floats, but only happens if the fields in the struct add up to a multiple of 8 bytes.