Question

I am trying to create a very simple ASP.NET page that allows a user to enter student data. When the form is submitted, the List of student objects is updated and the Repeater (which is databound to the list) reflects the new data. The user should be able to keep adding new students.

Mine fails to perform. I have no idea why. I have tried changing the postback and databinding methods many times.

   /*
     * Student class representing a real-life student.
     */
    public class Student
    {

        /* Override default constructor */
        public Student(string first, string last, string studentid, string program, string option)
        {
            FName = first;
            LName = last;
            STID = studentid;
            Program = program;
            Option = option;
        }

        /* Property for the student's first name */
        public string FName
        {
            set; get;
        }

        /* Property for the student's last name */
        public string LName 
        {
            set; get;         
        }

        /* Property for the student ID */
        public string STID
        {
            set; get;
        }

        /* Property for the program of study */
        public string Program
        {
            set; get;
        }

        /* Property for the option within the program of study */
        public string Option
        {
            set; get;
        }

    }

    /* Class for the web form UI */
    public partial class _Default : System.Web.UI.Page
    {

        /* List of students to be displayed in the repeater control */
        private List<Student> myStudents;

        protected void Page_Load(object sender, EventArgs e)
        {

            myStudents = new List<Student>();



            /* Check postback value when the page loads - this is the first time */
            if (IsPostBack == false)
            {
                /* Bind the Collection to the Repeater control */
                Label1.Text = "" + myStudents.Count;
                Repeater1.DataSource = myStudents;
                Repeater1.DataBind();
            }


        }

        /* 
         * Submit button clicked to submit the form.
         */
        protected void Button2_Click(object sender, EventArgs e)
        {

            /* The forum has passed all of the validation rules for this case and we can add a new student to the list */
             if(Page.IsValid) {

                /*if its valid then create a new student object to put into the list of students
                  get the data from POST*/
                 myStudents.Add(new Student(FNameTextBox.Text, LNameTextBox.Text, SIDTextBox.Text, POSDropDownList.SelectedItem.Text, POListBox.SelectedItem.Text));

                 Label1.Text = "" + myStudents.Count;


              }

        }
    }

Here is the code for the Repeater:

<asp:Repeater ID="Repeater1" runat="server">
  <HeaderTemplate>
         <table border="1">
            <tr>
               <td><b>First Name</b></td>
               <td><b>Last Name</b></td>
               <td><b>Student ID</b></td>
               <td><b>Program</b></td>
               <td><b>Option</b></td>
            </tr>
      </HeaderTemplate>

      <ItemTemplate>
         <tr>
            <td> <%# DataBinder.Eval(Container.DataItem, "FName")%> </td>
            <td> <%# DataBinder.Eval(Container.DataItem, "LName") %> </td>
            <td> <%# DataBinder.Eval(Container.DataItem, "STID")%> </td>
            <td> <%# DataBinder.Eval(Container.DataItem, "Program") %> </td>
            <td> <%# DataBinder.Eval(Container.DataItem, "Option") %> </td>
         </tr>
      </ItemTemplate>

      <AlternatingItemTemplate>
        <tr bgcolor="#e8e8e8">
          <td> <%# DataBinder.Eval(Container.DataItem, "FName")%> </td>
            <td> <%# DataBinder.Eval(Container.DataItem, "LName") %> </td>
            <td> <%# DataBinder.Eval(Container.DataItem, "STID")%> </td>
            <td> <%# DataBinder.Eval(Container.DataItem, "Program") %> </td>
            <td> <%# DataBinder.Eval(Container.DataItem, "Option") %> </td>
        </tr>
       </AlternatingItemTemplate>

      <SeparatorTemplate>
        <tr>
        <td colspan="5"><hr /></td>
        </tr>
      </SeparatorTemplate>

      <FooterTemplate>
         </table>
      </FooterTemplate>
</asp:Repeater>

Answer 1

I have refactored your code, now it should work

/* Class for the web form UI */
public partial class _Default : System.Web.UI.Page
{

    /* List of students to be displayed in the repeater control */
    private List<Student> myStudents = new List<Student>();

    protected void Page_Load(object sender, EventArgs e){

        /* Check postback value when the page loads - this is the first time */
        if (IsPostBack == false){
          this.bindRepeater();
        }
    }

 private void bindRepeater(){
  /* Bind the Collection to the Repeater control */
            Repeater1.DataSource = myStudents;
            Repeater1.DataBind();
            Label1.Text = "" + myStudents.Count;
            }

    /* 
     * Submit button clicked to submit the form.
     */
    protected void Button2_Click(object sender, EventArgs e)
    {

        /* The forum has passed all of the validation rules for this case and we can add a new student to the list */
         if(Page.IsValid) {

            /*if its valid then create a new student object to put into the list of students
              get the data from POST*/
             myStudents.Add(new Student(FNameTextBox.Text, LNameTextBox.Text, SIDTextBox.Text, POSDropDownList.SelectedItem.Text, POListBox.SelectedItem.Text));
             this.bindRepeater();


          }

    }
}