DataBinder.Eval and an ArrayList type property

[Mark Jones]

I am quite new to ASP and .Net development and I am building a web-based
multiple choice exam application.

The web page displays the questions using a Repeater control and the
answers are nested within the Repeater as RadioButtonLists. Simple
enough I think.

My data consists of a Question table and an Answer table. The Question
table has a QuestionID and a Question field. The Answer table has a
AnswerID field, an Answer field and a QuestionID foreign key (as each
answer belongs to only one question, each question can have one or more
answers).

My main question follows the code but the relevant parts of the code
behind file Exam.aspx.vb is as follows:


********************************************

Protected Sub Page_Load(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Me.Load

Dim allQuestionsAndAnswers As New ArrayList()
allQuestionsAndAnswers = GetAllQuestionsAndAnswers()

QuestionsAndAnswersRepeater.DataSource = allQuestionsAndAnswers
QuestionsAndAnswersRepeater.DataBind()

End Sub

Protected Function GetAllQuestionsAndAnswers() As ArrayList

Dim allQuestionsAndAnswersList As ArrayList = New ArrayList

Dim currentQuestion As QuestionDetails
Dim currentAnswerDetails As AnswerDetails
Dim currentQuestionAndAnswers As QuestionAndAnswers

<... Db connection code snipped ...>

While questionSqlDataReader.Read()
currentQuestion = New QuestionDetails()
currentQuestion.QuestionID = questionSqlDataReader.GetInt32(0)
currentQuestion.Question =
questionSqlDataReader.GetString(1).ToString
currentQuestion.QuestionType =
questionSqlDataReader.GetString(2).ToString

<... Db connection code snipped ...>

Dim tempAnswerDetailsList As New ArrayList

While answerSqlDataReader.Read()
currentAnswerDetails = New AnswerDetails()
currentAnswerDetails.AnswerID = answerSqlDataReader.GetInt32(0)
currentAnswerDetails.Answer = answerSqlDataReader.GetString(1)
tempAnswerDetailsList.Add(currentAnswerDetails)
End While

currentQuestionAndAnswers = New QuestionAndAnswers
currentQuestionAndAnswers.QuestionDetails = currentQuestion
currentQuestionAndAnswers.AnswerDetailsList = tempAnswerDetailsList

allQuestionsAndAnswersList.Add(currentQuestionAndAnswers)

End While

Return allQuestionsAndAnswersList


End Function


' Object to hold Question and related Answers

Protected Class QuestionAndAnswers

Private myQuestionDetails As QuestionDetails
Private myAnswers As ArrayList ' of AnswerHelper objects

Public Property QuestionDetails()
Get
Return myQuestionDetails
End Get
Set(ByVal value)
myQuestionDetails = value
End Set
End Property

Public Property AnswerDetailsList() As ArrayList
Get
Return myAnswers
End Get
Set(ByVal value As ArrayList)
myAnswers = value
End Set
End Property
End Class

'Object to hold question details

Protected Class QuestionDetails

Private myQuestionID As Integer
Private myQuestion As String
Private myQuestionType As String

Public Property QuestionID() As String
Get
Return myQuestionID
End Get
Set(ByVal value As String)
myQuestionID = value
End Set
End Property

Public Property Question() As String
Get
Return myQuestion
End Get
Set(ByVal value As String)
myQuestion = value
End Set
End Property

Public Property QuestionType() As String
Get
Return myQuestionType
End Get
Set(ByVal value As String)
myQuestionType = value
End Set
End Property
End Class

'Object to hold answer details

Protected Class AnswerDetails

Private myAnswerID As Integer
Private myAnswer As String

Public Property AnswerID() As Integer
Get
Return myAnswerID
End Get
Set(ByVal value As Integer)
myAnswerID = value
End Set
End Property

Public Property Answer() As String
Get
Return myAnswer
End Get
Set(ByVal value As String)
myAnswer = value
End Set
End Property
End Class

*********************************************

And the relevant part of the 'Exam.aspx' web page is:

<asp:Repeater ID="QuestionsAndAnswersRepeater" runat="server">
<HeaderTemplate>
<ol>
</HeaderTemplate>
<ItemTemplate>
<li>
<p>
<asp:Label runat="server" Font-Bold="true"
Font-Italic="true" Font-Size="Large" Text='<%#
DataBinder.Eval(Container.DataItem, "QuestionDetails.Question") %>'>
</asp:Label>
</p>
<p>
<asp:RadioButtonList runat="server" DataSource='<%#
DataBinder.Eval(Container.DataItem, "AnswerDetailsList") %>'>
</asp:RadioButtonList>
</p>
</li>
</ItemTemplate>
<FooterTemplate>
</ol>
<p>End of questions</p>
</FooterTemplate>
</asp:Repeater>


*************************************************


This works up to a point. The problem I have is with the line:

<asp:RadioButtonList runat="server" DataSource='<%#
DataBinder.Eval(Container.DataItem, "AnswerDetailsList") %>

This page when running currently looks something like this:

1. What is the average temperature of the sun?

o Exam+AnswerDetails o Exam+AnswerDetails o Exam+AnswerDetails

2. Who is the Prime Minister of the United Kingdom?

o Exam+AnswerDetails o Exam+AnswerDetails o Exam+AnswerDetails

etc. etc....

Now this is what I expect as AnswerDetailsList is an ArrayList object
and is being displayed via Object.ToString. But what I actually want to
display the Answer property within the AnswerDetails object but I don't
know make the DataBinder.Eval(container, expression) method navigate to
that property through an ArrayList object. Is this possible?

I may well need to redesign my objects to make the AnswerDetails.Answer
property more accessible to the server control in the page but I feel
the way I have done it is fairly logical and I'd rather not if there is
simpler solution in the web control.

Feel free to point out any other flaws in my code/design.

Thanks very much.