实体框架代码首先忽略了复杂类型

问题描述

我正在尝试创建一个包装器类型 EfObservableCollection< T> 围绕 ObservableCollection< T> 有一个额外的辅助属性来简化持久性（当然这个解决方案有权衡，但是，对我的域来说似乎是可行的）。

但是，类型 EfObservableCollection< T> 的属性似乎被忽略由EF。在数据库中没有创建适当的列。猜测实现 IEnumerable< T> 可能会触发EF忽略该类型，我评论了该实现，而不改变行为。

我在这里缺少什么？

实体类

  public class A 
 {
 [DataMember] 
 public long Id {get;组; } 
 
 [DataMember] 
 public string Text {get;组; 
 
 //标签不保留
 [DataMember] 
 public EfObservableCollection< string>标签{get;组; 
} 
  

包装类

  [ComplexType] 
 public class EfObservableCollection< T> ：IEnumerable< T> 
 {
 const string VALUE_SEPARATOR =\x8; //退格字符不太可能实际上是由用户输入的。假设ASCII或UTF-8。 
 readonly string [] VALUE_SEPARATORS = new string [] {VALUE_SEPARATOR}; 
 
 [NotMapped] 
 protected ObservableCollection< T>收藏{get;私人集合} 
 
 public EfObservableCollection（）
 {
 Collection = new ObservableCollection< T>（）; 
} 
 
 [DataMember] 
 public string PersistHelper 
 {
 get 
 {
 string serializedValue = string.Join（VALUE_SEPARATOR ，Collection.ToArray（））; 
 
 return serializedValue; 
} 
 set 
 {
 Collection.Clear（）; 
 string [] serializedValues = value.Split（VALUE_SEPARATORS，StringSplitOptions.None）; 
 foreach（string serializedValue in serializedValues）
 {
 Collection.Add（（T）Convert.ChangeType（serializedValue，typeof（T）））; // T必须实现IConvertable，否则运行时异常。 
} 
} 
} 
 
 public void Add（T item）
 {
 Collection.Add（item）; 
} 
 
 IEnumerator< T> GetEnumerator（）
 {
 return Collection.GetEnumerator（）; 
} 
 
 System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator（）
 {
返回GetEnumerator（）; 
} 
} 
  

解决方案

事实证明，实体框架不喜欢通用类 EfObservableCollection< T> 。

数据按预期持久化：

  [ComplexType] 
 public class EfObservableCollectionString：EfObservableCollection< string> ; 
 {
} 
  

Building on Ladislav's answer to

Entity Framework Code First and Collections of Primitive Types

I'm attempting to create a wrapper type EfObservableCollection<T> around an ObservableCollection<T> that has an additional helper property to simplify persistence (certainly this solution has trade-offs, but it's seems workable for my domain).

However, properties of type EfObservableCollection<T> seem to be ignored by EF. No appropriate columns are created in the database. Guessing that implementing IEnumerable<T> might trigger EF to ignore that type, I commented out that implementation with no change in behavior.

What am I missing here?

Entity Class

public class A
{
    [DataMember]
    public long Id { get; set; }

    [DataMember]
    public string Text { get; set; }

    // Tags is not persisted
    [DataMember]
    public EfObservableCollection<string> Tags { get; set; }
}

Wrapper Class

[ComplexType]
public class EfObservableCollection<T> : IEnumerable<T>
{
    const string VALUE_SEPARATOR = "\x8"; // Backspace character.  Unlikely to be actually entered by a user.  Assumes ASCII or UTF-8.
    readonly string[] VALUE_SEPARATORS = new string[] { VALUE_SEPARATOR };

    [NotMapped]
    protected ObservableCollection<T> Collection { get; private set; }

    public EfObservableCollection()
    {
        Collection = new ObservableCollection<T>();
    }

    [DataMember]
    public string PersistHelper
    {
        get
        {
            string serializedValue = string.Join(VALUE_SEPARATOR, Collection.ToArray());

            return serializedValue;
        }
        set
        {
            Collection.Clear();
            string[] serializedValues = value.Split(VALUE_SEPARATORS, StringSplitOptions.None);
            foreach (string serializedValue in serializedValues)
            {
                Collection.Add((T)Convert.ChangeType(serializedValue, typeof(T))); // T must implement IConvertable, else a runtime exception.
            }
        }
    }

    public void Add(T item)
    {
        Collection.Add(item);
    }

    IEnumerator<T> GetEnumerator()
    {
        return Collection.GetEnumerator();
    }

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}

解决方案

It turns out that Entity Framework does not like the generic class EfObservableCollection<T>.

If I derive a non-generic class from that class, data is persisted as expected:

[ComplexType]
public class EfObservableCollectionString : EfObservableCollection<string>
{
}

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