2

所以我有以下 ASP.NET 代码。本质上,我试图显示一个“考试”对象。考试由几个字符串组成,然后是嵌套的问题集合。问题具有嵌套的答案集合。当我运行它时,我收到一条错误消息:无法将“System.Char”类型的对象转换为“PracticeNet.DataEntities.Question”类型。

System.InvalidCastException:无法将“System.Char”类型的对象转换为“PracticeNet.DataEntities.Question”类型。

第 15 行:<%#:Item.QuestionTitle %>

我不知道为什么会收到此错误。我在 Question 类附近没有任何字符类型。我唯一的猜测是我从根本上误解了嵌套的 ListView 对象模型。任何人都可以对此有所了解吗?完整代码如下。

<asp:Content ID="Content2" ContentPlaceHolderID="FeaturedContent" runat="server">
    <asp:FormView ID="examDetails" runat="server" ItemType="PracticeNet.DataEntities.Exam" SelectMethod="GetExam" RenderOuterTable="false">
        <ItemTemplate>
            <div>
                <h1><%#:Item.ExamTitle %></h1>
                <h2><%#:Item.Description %></h2>
            </div>
            <br />
            <asp:ListView ID="examQuestions" runat="server" ItemType="PracticeNet.DataEntities.Question" DataSource="<%#:Item.Questions %>">
                <ItemTemplate>
                    <div>
                        <h1><%#:Item.QuestionTitle %></h1>
                        <h2><%#:Item.QuestionText %></h2>
                    </div>
                    <br />
                    <asp:ListView ID="questionAnswers" runat="server" ItemType="PracticeNet.DataEntities.Answer" DataSource="<%#:Item.AnswerOptions %>">
                        <ItemTemplate>
                            <div>
                                <h1><%#:Item.AnswerText %></h1>
                            </div>
                        </ItemTemplate>
                    </asp:ListView>
                </ItemTemplate>
            </asp:ListView>
        </ItemTemplate>
    </asp:FormView>
</asp:Content>
<asp:Content ID="Content3" ContentPlaceHolderID="MainContent" runat="server">
</asp:Content>

考试班:

public class Exam
    {
        [Required]
        public Guid ExamId
        {
            get;
            set;
        }
        [Required, StringLength(512),Display(Name="Title")]
        public string ExamTitle
        {
            get;
            set;
        }
        [Required, StringLength(1024),Display(Name="Details")]
        public string Description
        {
            get;
            set;
        }

        [Required]
        public virtual ICollection<Question> Questions
        {
            get;
            set;
        }
    }

问题分类:

public class Question
    {
        public Question()
        {
            QuestionId = Guid.NewGuid();
            AnswerOptions = new List<Answer>();
        }
        [Key]
        public Guid QuestionId
        {
            get;
            set;
        }
        [Required, StringLength(120), Display(Name="Title")]
        public string QuestionTitle
        {
            get;
            set;
        }
        [Required,StringLength(255), Display(Name="Text")]
        public string QuestionText
        {
            get;
            set;
        }
        [Required]
        public virtual ICollection<Answer> AnswerOptions
        {
            get;
            set;
        }
    }

最后,答案类:

public class Answer
    {
        public Answer()
        {
            AnswerId = Guid.NewGuid();
        }
        [Key]
        public Guid AnswerId
        {
            get;
            set;
        }
        [Required, StringLength(250), Display(Name="Answer")]
        public string AnswerText
        {
            get;
            set;
        }

    }
4

1 回答 1

2

(因为每个问题都需要答案形式的答案)

正如@James 和@debracey 的评论已经指出的那样,您的服务器标签的表述是错误的:

代替

<%#: Item.AnswerOptions %>

<%# Item.AnswerOptions %>
于 2015-03-12T15:51:30.233 回答