c# struct/class initilaze a Arraylist

I have this code :

 public struct SmartFilter
    {
        public int from, to;
        public Arra开发者_如何学运维yList collect  = new ArrayList();                 
        public long bit;            
    }

i get error :

cannot have instance field initializers in structs

i try different way to get over this error without success,

how to have a array list in struct / class?

There are multiple problems there:

• having a mutable struct - just evil
• having public fields
• using ArrayList

none of these is helping you...

with a class the initializer would work fine

with a property you could do lazy init:

public ArrayList Collect {
    get { return collect ?? (collect = new ArrayList()); }
}

I would refactor to:

public class SmartFilter
{
    public int From  {get;set;}
    public int To  {get;set;}
    private List<SomeKnownType> collect  = new List<SomeKnownType>();
    public List<SomeKnownType> Collect { get { return collect; } }
    public long Bit {get;set;}
}

Eh, I'll let the guys with bigger brains than me explain why, but you can't do that. :) However you could do this...

class NotAStruct
{
    public int from, to;
    public ArrayList collect = new ArrayList();
    public long bit;   
}

...or this...

struct Blah
{
    ArrayList doh;
    public void SomeMethod()
    {
        doh = new ArrayList();
    }
}

But neither is a good idea, as pointed out by several other people.

You should make a class of it, I wouldn't keep an ArrayList in a struct since struct should be used for simple data. Regarding the error you have I think you just can remove the new ArrayList(); and it should work.

I wrote this and it works just fine:

public struct MyStruct
{
    public int intVal;
    public ArrayList listVal;
    public bool boolVal;
}

However, I really thing you should use a class instead; that is, use this instead:

public class MyClass    {
    public int IntVal {get; set;}
    public ArrayList ListVal {get; set;}
    public bool BoolVal {get; set;}
}