This is not a solution, but can solve your update panel updating problem. You can control updatepanel update manually doing this:
<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="false">
<ContentTemplate>
<asp:DropDownList ID="DrpdwnLectureName" AutoPostBack="True" runat="server" OnSelectedIndexChanged="DrpdwnLectureName_SelectedIndexChanged"></asp:DropDownList>
<asp:Panel ID="PrintPanel" runat="server">
<asp:Label ID="Label1" runat="server" Text="Gör en .pdf på besvarade frågor"></asp:Label>
<asp:Button ID="btnDoPdf" runat="server" Text="Button" OnClick="btnDoPdf_Click" />
</asp:Panel>
<asp:Repeater ID="rptStudentQuestion" runat="server" OnItemCommand="rptStudentQuestion_ItemCommand" OnItemDataBound="rptStudentQuestion_ItemDataBound">
<ItemTemplate>
<asp:Label ID="lblQuestion" runat="server" Text='<%# Eval("StudentQuestionQuestion") %>'></asp:Label>
<br />
<asp:TextBox ID="tbxAnswer" runat="server" Visible="false"></asp:TextBox>
<asp:Button ID="btnSend" CommandName="SendAnswer" runat="server" Text="Skicka svar" CommandArgument='<%# Eval("StudentQuestionID") %>' />
<br />
<asp:Label ID="lblAnswer" runat="server" Text='<%# Eval("StudentQuestionAnswer") %>' Visible="false"></asp:Label>
<br />
</ItemTemplate>
</asp:Repeater>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="DrpdwnLectureName" />
</Triggers>
</asp:UpdatePanel>
and when you want to update the panel in code, you call: "UpdatePanel1.Update()"
if (item.LectureName == DrpdwnLectureName.SelectedValue)
{
var list = client.GetStudentQuestions(item.LectureID, user);
if (list.Count() > 0)
{
rptStudentQuestion.Visible = true;
rptStudentQuestion.DataSource = list;
rptStudentQuestion.DataBind();
}
else
{
rptStudentQuestion.Visible = false; // In debug it preforms this, but nothing happens.
UpdatePanel1.Update() //This 'force' updatepanel updating
}
}