Problem with List<>

[polomint]

Hi, I have a problem with VS2010beta2 and .NET Framework Client Profile, although I would expect the problem to be something to do with my inexperienced coding. I have this block of code..

    struct sGamePort
    {
        public string sgpProtocol;
        public UInt16 sgpPortStart;
        public UInt16 sgpPortEnd;
    }

    struct sGamePortItem
    {
        public string sgpName;
        public List<sGamePort> sgpPortList;
    }

    List<sGamePortItem> sGames;


    private sGamePort ParsePorts(string\[\] line)
    {
        sGamePort gp = new sGamePort();
        gp.sgpProtocol = line\[0\];
        int num = line.Count();
        if (num == 2)
        {
            // single port opened...
            gp.sgpPortStart =  Convert.ToUInt16(line\[1\]);
            gp.sgpPortEnd = Convert.ToUInt16(line\[1\]);
        }
        if (num == 3)
        {
            // port range opened...
            gp.sgpPortStart = Convert.ToUInt16(line\[1\]);
            gp.sgpPortEnd = Convert.ToUInt16(line\[2\]);
        }
        return gp;
    }

Where line is a string array which essentially holds some tokens. ie. line[0] = "NAME" line[1] = "JOHN" line[2] = "YOUNG" Now, in a seperate function I have

sGamePortItem pi = new sGamePortItem();
pi.sgpProtocol = "TCP";
pi.sgpPortList.Add(ParsePorts(strCMD));

This gives me a Null Reference Exception, so I changed it to this...

sGamePortItem pi = new sGamePortItem();
pi.sgpProtocol = "TCP";
sGamePort test = new sGamePort();
test = ParsePorts(strCMD);
pi.sgpPortList.Add(test); // ERROR HERE

Now, the error only occurs on the specified line above.. What am I doing wrong? Is it to do with me using the new keyword incorrectly? Or do I not use 'new'? Any help would be appreciated as this has been confusing me for a few hours now, lol Thanks again. John

Yippee Kai Yai Signed Polomint.......

[vtchris peterson]

The problem is that your line:

public List<sGamePort> sgpPortList;

should be:

public List<sGamePort> sgpPortList = new List<sGamePort>();

Need to assign a target to sgpPortList before you dereference it, hence the null ref exception.

[polomint]

Damn, I knew it would be something trivial... Thanks for waking me up to a silly mistake, :-D :-D :-D EDIT: Now I'm getting the error "cannot have instance field initializers in structs"... Hmmm, this could be a pain... EDIT AGAIN: I realised what was wrong.. I hadn't been initialising the sGamePortItem in the list..

sGamePortItem pi = new sGamePortItem();
pi.sgpPortList = new List<sGamePort>(); // THIS WAS NEEDED.

Thank you for your help, it made me think more about the initialisation...

Yippee Kai Yai Signed Polomint.......

modified on Thursday, December 3, 2009 2:09 PM

[puri keemti]

You need to initialize the list of the struct "sGamePortItem" before assigning the object.