如何获取自跟踪实体的主键?

最后,我创建了自己的属性并修改了T4模板,将该属性放在主键列的上方。以下是我采取的步骤:

1. <#if (ef.IsKey(edmProperty)) {#>    
   [PrimaryKeyAttribute]
   <#}#>
   

2. 创建PrimaryKeyAttribute:

   [AttributeUsage(AttributeTargets.Property)]
   public class PrimaryKeyAttribute : Attribute
   {}
   

3. private string GetPrimaryKey<K>()
   {
       string primaryKey = string.Empty;
   
       PropertyInfo[] entityProperties = typeof(K).GetProperties();
   
       foreach (PropertyInfo prop in entityProperties)
       {
           object[] attrs = prop.GetCustomAttributes(false);
           foreach (object obj in attrs)
           {
               if (obj.GetType() == typeof(PrimaryKeyAttribute))
               {
                   primaryKey = prop.Name;
                   break;
               }
           }
       }
   
       if (string.IsNullOrEmpty(primaryKey))
           throw new Exception("Cannot determine entity's primary key");
   
       return primaryKey;
   }
   

4. public T GetByID(int id)
   {
       return (T)context.GetObjectByKey(new EntityKey(context.DefaultContainerName 
                                           + "." + context.CreateObjectSet<T>().EntitySet.Name
                                           , GetPrimaryKey<T>(), id));            
   }
   

    _qualifiedTypeName = _context.DefaultContainerName + "." + _baseTypeName;
    Type baseType = GetBaseType(typeof(T));
    _baseTypeName = baseType.Name.ToString();

    PropertyInfo[] entityProperties = baseType.GetProperties();
    List<string> keyList = new List<string>();

    foreach (PropertyInfo prop in entityProperties) 
    {
      object[] attrs = prop.GetCustomAttributes(false);
      foreach (object obj in attrs)                
      {
        if (obj.GetType() == typeof(EdmScalarPropertyAttribute))
        {
          EdmScalarPropertyAttribute attr = (EdmScalarPropertyAttribute)obj;
          if (attr.EntityKeyProperty) keyList.Add(prop.Name);
         }
       }
    }
    if (keyList.Count > 0)
    {
      _keyName = keyList[0];
    }

然后你会像这样归还它:

EntityKey key = new EntityKey(_qualifiedTypeName, _keyName, id);
return (T)_context.GetObjectByKey(key);

看起来我从这里得到了上面的信息: http://blog.vascooliveira.com/how-to-check-for-an-entity-objects-entitykey-properties/

Here's another solution that uses the MetadataWorkspace...

1. Create a base DataAccess class with the following signature.

        public class DataAccessBase<TDataEntity> : IDisposable
            where TDataEntity : EntityObject

2. Create a method in DataAccessBase as the following...


    public TDataEntity GetByKey(object keyId)
            {
                // Get the entity key name
                var keyName = EntityContext.MetadataWorkspace
                                .GetEntityContainer(EntityContext.DefaultContainerName, DataSpace.CSpace)
                                .BaseEntitySets
                                .First(x => x.ElementType.Name == typeof(TDataEntity).Name)
                                .ElementType
                                .KeyMembers
                                .Select(key => key.Name)
                                .FirstOrDefault();

                // Get the Entity Set name
                var entitySet = (from container in EntityContext.MetadataWorkspace.GetItems<EntityContainer>(DataSpace.CSpace)
                                 from set in container.BaseEntitySets.OfType<EntitySet>()
                                 where set.ElementType.Name == typeof(TDataEntity).Name
                                 select set).FirstOrDefault();


                // Create qualified type name for entity
                string qualifiedTypeName = String.Format("{0}.{1}", EntityContext.DefaultContainerName, entitySet.Name);

                // Create the EntityKey
                EntityKey entityKey = new EntityKey(qualifiedTypeName, keyName, keyId);

                // Return object by it's entity key
                return (TDataEntity)EntityContext.GetObjectByKey(entityKey);
            }