Can we have genric Properties?

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Can we have a Generic properties?I have a requirement of storing the data.So i have taken class with Generic Properties.When i add the data to that Property am getting an error that "Object reference not set to an instance of an object" .please suggest me some idea.

class GeneralClass
    {
        private List<int> _student_rollnumber;
        public List<string> _student_name;
        public List<int> Student_RollNumber
        {
            get { return _student_rollnumber; }
            set { _student_rollnumber = value; }
        }
        public List<string> Student_Name
        {
            get { return _student_name; }
            set { _student_name = value; }
        }
    }

i have used the Class in Button Click.

private void btn_save_Click(object sender, EventArgs e)
      {
          try
          {
              GeneralClass obj = new GeneralClass();
              obj.Student_RollNumber.Add(int.Parse(txtbx_rollnum.Text));
              obj.Student_Name.Add(txtbx_SName.Text);
              MessageBox.Show("Data saved");
          }
          catch (Exception ex)
          {
              MessageBox.Show(ex.Message, "Message from form");
          }
      }

Posted 13-Sep-10 23:45pm

hemantwithu

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OriginalGriff · Accepted Answer · 2010-09-14T00:02:00

You need to assign an instance of your lists to each of the lists you are trying to use, as in:

private List<int> _student_rollnumber = new List<int>();

If you don't then when you try to use them you will get a null reference exception.
Additionally, don't use public on internal fields - it exposes your code internals to the outside world, and fixes you to use that for the rest of time. Instead, provide public properties and methods to manipulate internal data - that way you can change how you store information without changing the working code that uses your class.

By the way, I would have a class Student which had a roll number, and a name, then then set up a list of Students - that way the Student can take care of itself, it doesn't need to know other students even exist, much less how they are stored.

[edit]HTML characters fixed greater than disappearance.![/edit]