<asp:Repeater runat="server" ID="rQuestions">
        <ItemTemplate>
            <asp:Panel runat="server" GroupingText='<%# Eval("QuestionText") %>'>
                <asp:HiddenField ID="hfQuestionId" runat="server" Value='<%# Eval("QuestionId") %>' />
                <asp:Repeater runat="server" ID="rAnswers" DataSource='<%# Eval("Answers") %>'>
                    <ItemTemplate>
                        <div>
                            <asp:HiddenField ID="hfAnswerId" runat="server" Value='<%# Eval("AnswerId") %>' />
                            <asp:CheckBox ID="cbAnswer" runat="server" Text='<%# Eval("AnswerText") %>' />
                        </div>
                    </ItemTemplate>
                </asp:Repeater>
            </asp:Panel>
        </ItemTemplate>
    </asp:Repeater>
    <asp:Button ID="bSave" runat="server" Text="Сохранить" OnClick="btnSaveClick"/>

  public class Answer
        {
            public string AnswerText { get; set; }
            public int AnswerId { get; set; }
            public bool Selected { get; set; }
        }

        public class Question
        {
            public int QuestionId { get; set; }
            public string QuestionText { get; set; }
            public IEnumerable<Answer> Answers { get; set; }
        }
         
        protected void Page_Load(object sender, EventArgs e)
        {
            if (IsPostBack)
                return;

            var questions = new List<Question>
            {
                new Question
                {
                    QuestionId = 0,
                    QuestionText = "Вопрос 1 ?",
                    Answers = new List<Answer>
                    {
                        new Answer {AnswerId = 0, AnswerText = "Ответ 1_1"},
                        new Answer {AnswerId = 1, AnswerText = "Ответ 1_2"},
                    }
                },
                new Question
                {
                    QuestionId = 1,
                    QuestionText = "Вопрос 2 ?",
                    Answers = new List<Answer>
                    {
                        new Answer {AnswerId = 2, AnswerText = "Ответ 2_1"},
                        new Answer {AnswerId = 3, AnswerText = "Ответ 2_2"},
                        new Answer {AnswerId = 4, AnswerText = "Ответ 2_3"},
                    }
                },
            };

            rQuestions.DataSource = questions;
            rQuestions.DataBind();
        }

        protected void btnSaveClick(object sender, EventArgs e)
        {
            foreach (RepeaterItem  itemQ in rQuestions.Items)
            {
                var questionId = ((HiddenField)itemQ.FindControl("hfQuestionId")).Value;
                var answersRepeater = (Repeater)itemQ.FindControl("rAnswers");

                foreach (RepeaterItem itemAnsw in answersRepeater.Items)
                {
                    var answerId = ((HiddenField) itemAnsw.FindControl("hfAnswerId")).Value;
                    var @checked = ((CheckBox) itemAnsw.FindControl("cbAnswer")).Checked;
                    //TODO Save {QuestionId, AnswerId, Checked}
                }
            }
        }