How to use fields of a struct without assigning a value to them first?

Question

When defining a struct similar to System.Drawing.Point but with double instead of float: How to use X and Y without assigning a value to them first?

Example:

public struct PointD
{
    public double X;
    public double Y;
}

static void Main()
{
    PointD testPointD;
    double d = testPointD.X; // CS0170: Use of possibly unassigned field 'X'
    
    
    System.Drawing.Point point;

    // Here I can use X without defining it first.
    // So I guess the struct is doing something to make that work?
    // Edit: This also doesn't work, but Visual Studio did not underline it,
    // my fault!
    int i = point.X;
}

Answer 1

You are mistaken. The code you talked about woks just fine and there is no difference between PointF and your PointD:

    public Form1()
    {
        InitializeComponent();

        MyStruct ms = new MyStruct();
        this.Text = ms.p.X.ToString() + ms.d.X.ToString();

    }

    public struct PointD
    {
        public double X;
        public double Y;
    }

    public struct MyStruct
    {
        public PointF p;
        public PointD d;
    }

The title of form1 shows "00" as expected.

Edit:

Maybe you are wondering why you get a complier error when you try to use a struct directly, that was not created but do not get an error when you use an un-created struct within a struct. Or one within a struct within a struct within a struct within a struct..

Which should make it clear: The compiler doesn't follow these levels of nesting; it just flags things that are obvious to it, that is omissions within its direct scope.

Granted, this can be a nuisance but all in all I'm glad to be warned instead of being allowed to forget initialization.