How to get object property from a collection

Question

In order to eliminate the need to write a really long Switch Statement, I want to get the object property from a collection that contains data.

Here is my code:

public class NCAABArchive 
{
    private int id;
    public int HScore;
    public string Road;
    public int RScore;
    public double Line;
    public double LineAvg;
    public double LineSag;
    public double LineSage;
    public double LineSagp;
    public double LineSggm;
    public double LineMoore;


}


        string forecastStr = "coll.LineFox";
        string actualStr = "coll.ActualSpread";

        foreach (NCAABArchive coll in Form1.gui.NCAABArchiveCollection)
        {
            recCtr++;

//System.NullReferenceException // HResult=0x80004003 // Message=Object reference not set to an instance of an object. // Source=BBallStatsPredictions

            //PropertyInfo pinfo = typeof(NCAABArchive).GetProperty(forecastStr);
            //object value = pinfo.GetValue(coll);

            if (recCtr % 100 == 0)
            {
                if (coll.GameScore != null)
                {
                    switch (forecastStr)
                    {
                        case "coll.LineAvg":
                            altargetforecast.Add(coll.LineAvg);
                            break;

                        case "coll.LineSag":
                            altargetforecast.Add(coll.LineSag);
                            break;

                        case "coll.LineSggm":
                            altargetforecast.Add(coll.LineSggm);
                            break;

                        case "coll.LineFox":
                            altargetforecast.Add(coll.LineFox);
                            break;

                        default:
                            break;
                    }

                    //altargetforecast.Add(coll.LineAvg);
                    //alactual.Add(coll.ActualSpread);

                    // altargetforecast.Add(forecastStr);
                    alactual.Add(coll.ActualSpread);
                }
            }

I'm getting an Error Message=Object reference not set to an instance of an object.

How do I instantiate the object, the collection already is instantiated? What am I doing wrong?

Whinch line in this code is the null reference exception being raised? — Chris Schaller, Jan 27 '21 at 23:23
after I un-comment and run the "object value=pinfo line. I get the error — Trey Balut, Jan 28 '21 at 01:12

score 0 · Answer 1 · answered Jan 27 '21 at 23:22

0

Your forecastStr is not the property name. It is "coll.{propertyname}".

The problem is that your line:

PropertyInfo pinfo = typeof(NCAABArchive).GetProperty(forecastStr);

is not getting a property because there's not a property called "coll.Linefox".

So pinfo is null and returning the error when you try to access it.

string propName = "LineAvg"
PropertyInfo pinfo = typeof(NCAABArchive).GetProperty(propName);
object value = pinfo.GetValue(coll)

// "value" will be set to coll.LineAvg

answered Jan 27 '21 at 23:22

Neil W

7,670
3
28
41

Still getting the error: System.NullReferenceException HResult=0x80004003 Message=Object reference not set to an instance of an object. at the pinfo.GetValue(coll) line. – Trey Balut Jan 28 '21 at 01:08
Where are you getting the error. On the GetProperty line, or the GetValue line? If the latter, check if pinfo is null. – Neil W Jan 28 '21 at 12:45
Neil, I'm getting the error on the GetValue line. Error says "pinfo is null" – Trey Balut Jan 28 '21 at 14:30
And what is your "forecastStr" set to at the time? – Neil W Jan 28 '21 at 21:00

How to get object property from a collection

1 Answers1