尝试JsonConvert.SerializeObject时从“ ServerVersion”获取值时出错

Question

I have a very basic code using Entity Framework to get a model in my MVC C# .NET Controller.

var myModel = myContext.MyData
                .Where(m => m.ID == 1)
                .FirstOrDefault();

string json = Newtonsoft.Json.JsonConvert.SerializeObject(myModel);

When I try to run this code, I get an error:

Error getting value from ServerVersion on System.Data.SqlClient .

... If I press Continue , the view says:

[InvalidOperationException: Invalid operation. The connection is closed.]

What's wrong? What does SQL have to do with this? The same error comes if I do this in the View instead of the Controller.

Edit:

My class (model)

namespace TrackerEntityFrameworks.Models
{
  public class MyData: DbContext
  {
    [Key]
    public int ID { get; set; }
    [Required]
    public string Name { get; set; }
    [Required]
    public DateTime StartTime { get; set; }
    [Required]
    public DateTime EndTime { get; set; }

    public ICollection<TripRecord> TripRecords { get; set; }
    public ICollection<TollRecord> TollRecords { get; set; }
  }
}

Answer 1

You're Trying to serialize the entire Dbcontext , don't do that!

Remove the inheritance of MyData from DbContext and you should be fine.

Your business class must be "persistance ignorant", in order to be reusable and Entity Framework works perfectly in this way

Answer 2

Seperate the DbContext from your entity then do the following:

namespace TrackerEntityFrameworks.Structure
{
  public class MyContext: DbContext
  {
    public DbSet<TripRecord> TripRecords { get; set; }
    public DbSet<TollRecord> TollRecords { get; set; }
    public DbSet<MyData> MyDatas { get; set; }
  }
}

namespace TrackerEntityFrameworks.Models
{
  public class MyData
  {
    [Key]
    public int ID { get; set; }
    [Required]
    public string Name { get; set; }
    [Required]
    public DateTime StartTime { get; set; }
    [Required]
    public DateTime EndTime { get; set; }

    // navigation properties: check how to implement relationships in EF Code First
    public ICollection<TripRecord> TripRecords { get; set; }
    public ICollection<TollRecord> TollRecords { get; set; }
  }
}


using(var myContext = new TrackerEntityFrameworks.Structure.MyContext())
{
  var result = myContext.MyDatas
                  .Where(m => m.ID == 1)
                  .FirstOrDefault();
  string json = Newtonsoft.Json.JsonConvert.SerializeObject(result);
}

Entity framework tutorial: http://www.entityframeworktutorial.net/code-first/entity-framework-code-first.aspx