2
所以我有以下的ASP.NET代码。本质上,我试图展示一个“考试”对象。考试由几个字符串组成,然后是问题的嵌套集合。问题有一个嵌套的答案集合。当我运行它时,我收到一个错误消息: 无法投射'System.Char'类型的对象以键入'PracticeNet.DataEntities.Question'。ASP.NET嵌套的ListView数据绑定
System.InvalidCastException:无法将类型为 'System.Char'的对象强制类型为'PracticeNet.DataEntities.Question'。
线15:<%#:Item.QuestionTitle%>
我不知道为什么我收到这个错误。我在Question类的任何地方都没有任何字符类型。我唯一的猜测是,我有点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>
考试类别:
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;
}
}
问题类别:
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;
}
}
我相信你正在使用“DataSource”字段的错误ASP标记。它应该是'<%#Item.AnswerOptions%>'你有':'在那里是不必要的。 – debracey
你试过用'<%#'替换'<%#:'看起来有嫌疑吗? – James
是的,用<%#替换<%#:似乎已经做到了。谢谢! – GWLlosa