问题描述
我是Linq和EF Code First的新手，遇到了一个我根本无法想象的问题。我正在使用ASP.Net Web Forms，EF Code First和Linq开发概念验证程序。想法是我基于数据库动态生成页面的服务器控件。在没有EF的情况下，我已经构建了同样的应用程序，但希望能够了解到这个项目。我可以得到正确的结果，如果我使用文字，但收到一个错误，而数据绑定一个RadioButtonList。 DataBinding：'系统。 Data.Entity.DynamicProxies.Choice_EA448AD48C19F54FBB6BF09B7A03BA899DBE75EC189635A8982E7C3B1D8F4ABD'不包含名称为4的属性。
第34行：content.Controls.Add（ql）;
第35行：ql.DataSource =选择;
第36行：ql.DataBind（）;
行37：}
名称为4的属性只是一个值从我的数据库。我不知道这个问题是否与Lazy Loading有关，或者只是缺乏适当的Linq知识，但如果有人能指出我正确的方向，我会非常感激。
这是我正在使用的三个Class文件以及我正在尝试构建的C＃页面。请记住，我打算将数据访问分成另一个类，但只是试图为自己做一个演示。
Exam.cs
using System;
使用System.Collections.Generic;
使用System.Linq;
使用System.Web;
使用System.ComponentModel.DataAnnotations;
///< summary>
/// Exam的简要说明
///< / summary>
public class Exam
{
public int ExamId {get;组; }
public string标题{get;组; }
public string描述{get;组; }
public bool Status {get;组; }
public DateTime DateCreated {get;组; }
public string CreatedBy {get;组; }
public virtual ICollection< Question>问题{get;组; }
}
Question.cs
使用系统;
使用System.Collections.Generic;
使用System.Linq;
使用System.Web;
///< summary>
/// Question
的总结说明///< / summary>
public class Question
{
public int QuestionId {get;组; }
public string QuestionText {get;组; }
public int Order {get;组; }
public DateTime DateCreated {get;组; }
public bool Status {get;组; }
public string CreatedBy {get;组; }
public string QuestionType {get;组; }
public int ExamId {get;组; }
public virtual考试考试{get;组; }
public virtual ICollection< Choice>选择{get;组; }
}
Choice.cs
使用系统;
使用System.Collections.Generic;
使用System.Linq;
使用System.Web;
///< summary>
/// Choice的摘要说明
///< / summary>
public class Choice
{
public int ChoiceId {get;组; }
public string ChoiceText {get;组; }
public int Order {get;组; }
public bool Status {get;组; }
public bool Correct {get;组; }
public DateTime DateCreated {get;组; }
public string CreatedBy {get;组; }
public int QuestionId {get;组; }
public virtual问题问题{get;组; }
}
Testing.aspx.cs
使用系统;
使用System.Collections.Generic;
使用System.Linq;
使用System.Web;
使用System.Web.UI;
使用System.Web.UI.WebControls;
public partial class测试：System.Web.UI.Page
{
protected void Page_Load（object sender，EventArgs e）
{
ExamsContext db = new ExamsContext（）;
var questions =（from c in db.Exams
from c in c.Questions
其中c.ExamId == 1
select q）.ToList（） ;
ContentPlaceHolder content =（ContentPlaceHolder）this.Master.FindControl（MainContent）;
foreach（问题中的var问题）
{
文字问题Label = new Literal（）;
questionLabel.Text = Convert.ToString（question.QuestionId）+。& nbsp; + question.QuestionText +< br />;
content.Controls.Add（questionLabel）;
var choices =（from c in question.Choices select c）.ToList（）;
RadioButtonList ql = new RadioButtonList（）;
foreach（var choice in choices）
{
ql.DataValueField = Convert.ToString（choice.ChoiceId）;
ql.DataTextField = choice.ChoiceText;
}
content.Controls.Add（ql）;
ql.DataSource =选择;
ql.DataBind（）;
}
}
}
这是一段时间，因为我使用ASP.NET WebForms，但我认为你的问题在这里：
ql.DataValueField = Convert.ToString（choice.ChoiceId）;
ql.DataTextField = choice.ChoiceText;我认为 Convert.ToString（choice.ChoiceId）告诉控件使用名为4的属性。
尝试这样：
ql.DataValueField =ChoiceId;
ql.DataTextField =ChoiceText;
ie。您需要指定要使用的属性的名称，而不是值
I am new to Linq and EF Code First and came across an issue that I just can't figure out. I am developing a proof of concept examination program using ASP.Net Web Forms, EF Code First and Linq. The ideas is that I generate the page's server controls dynamically based on the database. I've built this same application before without EF but was hoping to learn that on this project. I can get the correct results if I use a literal but am receiving an error while databinding a RadioButtonList.
DataBinding: 'System.Data.Entity.DynamicProxies.Choice_EA448AD48C19F54FBB6BF09B7A03BA899DBE75EC189635A8982E7C3B1D8F4ABD' does not contain a property with the name '4'.
Line 34: content.Controls.Add(ql);
Line 35: ql.DataSource = choices;
Line 36: ql.DataBind();
Line 37: }
The property with the name of '4' is just a value from my database. I'm not sure if this problem is related to Lazy Loading or just lack of knowledge in proper Linq but I would really appreciate it if someone can point me in the right direction.
Here are my three Class files I am using and the C# page that I am trying to build. Keep in mind I plan to separate the data access into another class but was just trying to get a demo working for myself.Exam.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ComponentModel.DataAnnotations;
/// <summary>
/// Summary description for Exam
/// </summary>
public class Exam
{
public int ExamId { get; set; }
public string Title { get; set; }
public string Description { get; set; }
public bool Status { get; set; }
public DateTime DateCreated { get; set; }
public string CreatedBy { get; set; }
public virtual ICollection<Question> Questions { get; set; }
}
Question.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
/// <summary>
/// Summary description for Question
/// </summary>
public class Question
{
public int QuestionId { get; set; }
public string QuestionText { get; set; }
public int Order { get; set; }
public DateTime DateCreated { get; set; }
public bool Status { get; set; }
public string CreatedBy { get; set; }
public string QuestionType { get; set; }
public int ExamId { get; set; }
public virtual Exam Exam { get; set; }
public virtual ICollection<Choice> Choices { get; set; }
}
Choice.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
/// <summary>
/// Summary description for Choice
/// </summary>
public class Choice
{
public int ChoiceId { get; set; }
public string ChoiceText { get; set; }
public int Order { get; set; }
public bool Status { get; set; }
public bool Correct { get; set; }
public DateTime DateCreated { get; set; }
public string CreatedBy { get; set; }
public int QuestionId { get; set; }
public virtual Question Question { get; set; }
}
Testing.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class Testing : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
ExamsContext db = new ExamsContext();
var questions = (from c in db.Exams
from q in c.Questions
where c.ExamId == 1
select q).ToList();
ContentPlaceHolder content = (ContentPlaceHolder)this.Master.FindControl("MainContent");
foreach (var question in questions)
{
Literal questionLabel = new Literal();
questionLabel.Text = Convert.ToString(question.QuestionId) + ". " + question.QuestionText + "<br/>";
content.Controls.Add(questionLabel);
var choices = (from c in question.Choices select c).ToList();
RadioButtonList ql = new RadioButtonList();
foreach (var choice in choices)
{
ql.DataValueField = Convert.ToString(choice.ChoiceId);
ql.DataTextField = choice.ChoiceText;
}
content.Controls.Add(ql);
ql.DataSource = choices;
ql.DataBind();
}
}
}
解决方案 It's a while since I used ASP.NET WebForms, but I think your problem is here:
ql.DataValueField = Convert.ToString(choice.ChoiceId);
ql.DataTextField = choice.ChoiceText;
I think that Convert.ToString(choice.ChoiceId) is telling the control to use a property named "4".
Try this:
ql.DataValueField = "ChoiceId";
ql.DataTextField = "ChoiceText";
i.e. you need to specify the name of the property to use, not the value
这篇关于我如何解决这个“System.Data.Entity.DynamicProxies”错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！