arrays in classes

Question

Hi,
My first trys at using an array of classes; I get a null reference exception. A very simple test program:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace ArrayInClass
{
summary
Interaction logic for MainWindow.xaml
summary
public partial class MainWindow  Window
{
public class tmHgt
{
public string time;         time
public string hgt;          height
}
public class T_RefOut
{
public int mo;              month
public int day;             day
public tmHgt[] tmh = new tmHgt[5];
};
public T_RefOut[] TRefOuts;
public MainWindow()
{
InitializeComponent();
}
private void button1_Click(object sender, RoutedEventArgs e)
{
TRefOuts = new T_RefOut[28];
for (int i1 = 0; i1  28; i1++)
{
TRefOuts[i1].mo = 0;
TRefOuts[i1].day = 0;
for (int i2 = 0; i2  5; i2++)
{
TRefOuts[i1].tmh[i2].time = ;
TRefOuts[i1].tmh[i2].hgt = ;
}
}
}
}
}
Would appreciate any help. Thanks.  -Lew

Lewis · Answer

Mike,
Many thanks. That makes sense. I'll do that now :-)
- Lew

Mike Gold · Answer

I ran your program.   The reason you are getting a null reference is that you are newing up the array, but you are not newing up the element in the array.  This is a common mistake, and I've done it before myself
Here is the right way to do this:
private void button1_Click( object sender, RoutedEventArgs e)
{
TRefOuts = new T_RefOut [28];
for ( int i1 = 0; i1 new T_RefOut ();
TRefOuts[i1].mo = 0;
TRefOuts[i1].day = 0;
for ( int i2 = 0; i2 new tmHgt ();
TRefOuts[i1].tmh[i2].time = i2.ToString();
TRefOuts[i1].tmh[i2].hgt = i1.ToString();
}
}
}