array declaration in structure

Question

4.00/5 (1 vote)

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Hi!
how an array is declare in structure??

C#

public struct test
{
    public byte itemcode;
    public byte[] itemname;
    ////20
    public  byte method;
    public string[] controlname4QC;
    //  public string reserved;
    public byte[] reserved;
    public void initialize()
    {
        for (int i = 0; i < 20; i++)
        {
            reserved[i] = 0;
            controlname4QC[i] = "0";
        }
             
    }

    //test* p;
}

Is this code correct?

Posted 13-Aug-14 21:44pm

Member 10994712

Updated 21-Aug-14 5:17am

Afzaal Ahmad Zeeshan

v2

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Comments

Kornfeld Eliyahu Peter 14-Aug-14 3:51am

No.
1. Why struct and not class?
2. Why special initialization method instead of standard constructor?
3. Where you initialize those arrays? Nowhere I can see, so putting values at position i will cause troubles...

Member 10994712 14-Aug-14 4:30am

at first time i declared tha array as
public byte[] itemname=new byte[20];
but at that time i got an error that
Error 1 'structuretest.Form1.test.itemname': cannot have instance field initializers in structs C:\Users\ADL65654\Desktop\128.14pointerunofinal\structuretest - Copy\structuretest\Form1.cs 25 27 structuretest

Kornfeld Eliyahu Peter 14-Aug-14 4:35am

One more reason not to use struct...
See OGs' answer and the article in my comment...

3 solutions

Solution 3

This is a class with the same members of your struct, this is the best I can do for you.

C#

public class Test
    {
        public byte Itemcode{get; set;}
        public byte[] Itemname{get; set;}

        public byte Method { get; set; }
        public string[] Controlname4QC { get; set; }
        //  public string reserved;
        public byte[] Reserved{get; set;}
        public Test()
        {
            Itemcode = 0;
            Itemname = new byte[20];
            Method = 0;
            Controlname4QC = new string[20];
            Reserved = new byte[20];
        }
    }

Posted 21-Aug-14 4:48am

Enrique J. Gonzalez Fernandez

Solution 4

It can be done in a stuct with a constructor like:

C#

public struct ProofWithStruct
    {

        public ProofWithStruct(int charArraySize)
                : this()
            {
                domain = new char[charArraySize];
                Peers = new int[20];
                NumberOfPeers = 20;
                assignValue = '[';
            }

            public char[] domain;
            public int[] Peers;
            public int NumberOfPeers;
            public char assignValue;
    }

but keep the maximum of 16 bytes for your struct in mind or you like to have performance issues.

Posted 21-Aug-14 5:08am

Herman<T>.Instance

Updated 21-Aug-14 5:26am

v2

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OriginalGriff · Accepted Answer · 2014-08-13T22:00:00

Solution 1

No.
An array is a reference type, not a value type, and so to use it you need to allocate the space on the heap via the new keyword.
You don't do that, so you will get null reference errors when you try to access the arrays.

In addition, as Eliyahu has said, you should use the standard constructor instead of "inventing" your own.

Plus, that is probably above the maximum size guidelines for a struct which is 16 bytes: remember that each reference will take either 4 or 8 bytes depending on the 32/64 bit nature of your application / OS.

It looks like you are trying to "match" a c / c++ structure for intercommunication - if so, then you need to think rather more carefully about it: a reference is not the same as a pointer!

Posted 13-Aug-14 22:00pm

OriginalGriff

Comments

Kornfeld Eliyahu Peter 14-Aug-14 4:11am

http://www.codeproject.com/Articles/728836/Using-struct-and-class-whats-that-all-about

OriginalGriff 14-Aug-14 4:26am

I've seen that before somewhere! :laugh:

Member 10994712 14-Aug-14 4:27am

then how can i do that..can u please correct my code?

OriginalGriff 14-Aug-14 4:43am

Well - no, because it looks like it's not your code anyway, and you would seem to have copied it from C/C++ and just filed the serial numbers off! :laugh:

You can't do that: C# and C++ are very different languages which share a common syntax. You need to look carefully at what you started with (and how you are going to use it) rather than blindly translating. That is a recipe for a lot of problems later!

Member 10994712 21-Aug-14 7:21am

[MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
public byte[] itemname;
is this possible?

Afzaal Ahmad Zeeshan 21-Aug-14 11:19am

Please first learn the syntax brother.

[no name] 15-Aug-14 9:14am

5+. Good points.