cannot have instance field initializers in struct

Question

I'm not so experienced in C#, I'm used to work in java. I've already asked for something before and some people advised me this. link to my old topic here But I have new problem with this code. The Visual Studio says that "I cannot have instance filed initializers in struct" - so there is some problem but I really don't understand this thing so is somehow possible make this work?? I just need anchors type Vector3 which is matrix or array of arrays - whatever 4x4 In java I'll probably write it public Vector3[][] = new Vector3[4][4];

This is my problematic code:

  [StructLayout(LayoutKind.Sequential)]
    struct BPatch
    {
        public Vector3[][] anchors = new Vector3[][] {new Vector3[4],new Vector3[4],new Vector3[4],new Vector3[4]};
        public uint dlBPatch;// Display list
        public uint texture;// Texture
    }

possible duplicate of "cannot have instance field initializers in structs" problem — nawfal
– nawfal, Commented Apr 15, 2013 at 10:42

Marc Gravell · Accepted Answer · 2011-12-31 19:15:34Z

1

By the time you've got 5 arrays, you might as well just make it a class. It will behave more sensibly:

class BPatch
{
    private readonly Vector3[][] anchors = new Vector3[][] {new Vector3[4],new Vector3[4],new Vector3[4],new Vector3[4]};
    public Vector3[][] Anchors { get { return anchors; } }
    public uint DlBPatch {get;set;}
    public uint Texture {get;set;}
}

If you have good reason to micro-optimize, a "fixed" array (rather than a jagged array) might be interesting.

answered Dec 31, 2011 at 19:15

Marc Gravell

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4 Comments

user1097772 Over a year ago

And if I also need to set the anchors?? Why you used readonly?? I really don't much uderstand difference between fixed and jagged array. I found out that jagged array is array of array - thats only I know.

Marc Gravell Over a year ago

@user1097772 fixed sized arrays (fixed buffers) are an advanced technique in structs using "unsafe" code to embed a buffer directly in a struct. Hardcore stuff. You could make the outer array read-write. But in most cases that is an error; the intent is usually to change the contents, not to reassign the array. It is your type - do as you will. I should also add: most times, when someone new to c# uses a struct, they use it both inappropriately and incorrectly. Just saying...

user1097772 Over a year ago

Thx. I just need to do this: Bpatch bpatch = new Bpatch(); bpatch.anchors[0][1] = new Vector3(-0.75f,-0.75f,-0.5f); bpatch.anchors[0][2] = new Vector3(-0.25f,-0.75f,0.0f); etc.. Is that possible with readonly qualifier? My first intent was have anchors as matrix 4x4

Marc Gravell Over a year ago

@user1097772 yes; that doesn't reassign the array - should work fine

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