OlEdB Exception was unhandled by usercode - asp.net

Question

I keep getting the above error when trying to enter my value from a dropdownlist and my value from a GridViewRow.
It also says "Data Type Mismatch in Criteria Experession", I'm pulling the ID's of a Question and Paper from either the list/row and inputting them into my database.
Here's the code presenting the error.
Using con As New OleDb.OleDbConnection(ConfigurationManager.ConnectionStrings.Item("ConnectionString").ConnectionString)
con.Open()
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
Dim QuestionID As String = (checkedRow.Cells(0).Text)
Dim PaperID As String = DropDownList1.SelectedValue
Dim insertExamQuery = "INSERT INTO QuestionInPaper VALUES ('QuestionID', 'PaperID');"
Dim insertExamCmd = con.CreateCommand()
insertExamCmd.CommandText = insertExamQuery
insertExamCmd.ExecuteNonQuery()
Next
End Using
Here's the aspx all of this refers to:
<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>
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
ProviderName="<%$ ConnectionStrings:ConnectionString.ProviderName %>"
SelectCommand="SELECT [QuestionID], [Answer], [Question], [SubjectID] FROM [Question]">
</asp:SqlDataSource>
<asp:DropDownList ID="DropDownList1" runat="server"
DataSourceID="SqlDataSource3" DataTextField="PaperID" DataValueField="PaperID">
</asp:DropDownList>
Can you see where this mismatch is? ANy help is appreciated.

Answer 1

You are saying both your fields in QuestionInPaper are Numeric type, yet you are trying to insert string data - 'QuestionID' and 'PaperID'. You need to add them as parameters to your command. Also you are creating them as String, both types in code and database should be equal.
Using con As New OleDb.OleDbConnection(ConfigurationManager.ConnectionStrings.Item("ConnectionString").ConnectionString)
con.Open()
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
'// change type and parse
Dim QuestionID As Decimal = Decimal.Parse(checkedRow.Cells(0).Text)
Dim PaperID As Decimal = Decimal.Parse(DropDownList1.SelectedValue)
'// changed
Dim insertExamQuery = "INSERT INTO QuestionInPaper (QuestionID, PaperID) VALUES (?, ?);"
Dim insertExamCmd = con.CreateCommand()
'// added below
insertExamCmd.Parameters.Add("#QuestionID", OleDb.OleDbType.Numeric).Value = QuestionID
insertExamCmd.Parameters.Add("#PaperID", OleDb.OleDbType.Numeric).Value = PaperID
'// end add
insertExamCmd.CommandText = insertExamQuery
insertExamCmd.ExecuteNonQuery()
Next
End Using