Connecting dropdown to database - asp.net

Question

I asked a question a week ago on how to connect my checkbox to a database but i realised my database would not function the way i wanted it to due to a many to many problem.
So now the user will select a 'question' then select from the dropdown what 'paperID' the new test will have.
So i need to be able to retrieve the paperID from the dropdown and the QuestionID from the selected rows and save them under in a new table.
Here is my current code behind for the 'TestCreation' page which will compile both the PaperID and the 'QuestionID' into the 'QuestionInPaper' Table.
Public Class testcreation1
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Session.Item("User Type") <> "Teacher" Then
Response.Redirect("/")
End If
End Sub
Protected Sub QuestionCompiler_Click(sender As Object, e As EventArgs) Handles QuestionCompiler.Click
Dim allCheckedRows = From row In CreateTest.Rows.Cast(Of GridViewRow)()
Let chkQuestion = DirectCast(row.FindControl("QuestionSelector"), CheckBox)
Where chkQuestion.Checked
Select row
For Each checkedRow As GridViewRow In allCheckedRows
' implement the save function for this row '
Dim QuestionID As Int32 = Int32.Parse(checkedRow.Cells(0).Text)
' ... '
Next
End Sub
End Class
Source Code:
<h1>Compile Your Tests</h1>
<asp:GridView ID="CreateTest" runat="server"
AllowSorting="True" AutoGenerateColumns="False" CellPadding="4"
DataKeyNames="QuestionID" DataSourceID="SqlDataSource1" ForeColor="#333333"
GridLines="None">
<AlternatingRowStyle BackColor="White" ForeColor="#284775" />
<Columns>
<asp:TemplateField HeaderText="Select">
<ItemTemplate>
<asp:CheckBox ID="QuestionSelector" runat="server" />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="QuestionID" HeaderText="QuestionID"
InsertVisible="False" ReadOnly="True" SortExpression="QuestionID" />
<asp:BoundField DataField="Answer" HeaderText="Answer"
SortExpression="Answer" />
<asp:BoundField DataField="Question" HeaderText="Question"
SortExpression="Question" />
<asp:BoundField DataField="SubjectID" HeaderText="SubjectID"
SortExpression="SubjectID" />
<asp:TemplateField></asp:TemplateField>
</Columns>
<EditRowStyle BackColor="#999999" />
<FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
<RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
<SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
<SortedAscendingCellStyle BackColor="#E9E7E2" />
<SortedAscendingHeaderStyle BackColor="#506C8C" />
<SortedDescendingCellStyle BackColor="#FFFDF8" />
<SortedDescendingHeaderStyle BackColor="#6F8DAE" />
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
ProviderName="<%$ ConnectionStrings:ConnectionString.ProviderName %>"
SelectCommand="SELECT [QuestionID], [Answer], [Question], [SubjectID] FROM [Question]">
</asp:SqlDataSource>
<h5>Choose A Paper ID to compile your questions into</h5>
<asp:DropDownList ID="DropDownList1" runat="server"
DataSourceID="SqlDataSource3" DataTextField="PaperID" DataValueField="PaperID">
</asp:DropDownList>
<asp:SqlDataSource ID="SqlDataSource3" runat="server"
ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
ProviderName="<%$ ConnectionStrings:ConnectionString.ProviderName %>"
SelectCommand="SELECT [PaperID] FROM [ExamPaper]"></asp:SqlDataSource>
<asp:Button ID="QuestionCompiler" runat="server" Text="Compile Selected Questions" />
<h1>Preview Previous Tests</h1>
</asp:Content>
So as you can see from the code behind i've already had help with finding the rows of data, but how do I do the same with the checkbox in order to insert both of the QuestionID and PaperID into the QuestionInPaper table in my database. (The main problem is retrieving the value inside the checkbox.
Any help is appreciated!