有没有简单的方法将属性添加到 Linq to Sql 生成的实体以引用其 DataContext？例如：
var myContext = new DataContext();
var product = context.Products.Where(p => p.Id == productId).SingleOrDefault();
并且产品实体有一个名为“Context”(product.Context) 的属性，它引用了 myContext，datacontext。
我知道如何自定义生成的实体。我的问题是如何自定义（我认为是 DataContext）来设置它为自己创建的每个实例的“上下文”属性。
我不确定我是否做对了。我想用更少的代码编写一个性能最好的业务封装模型。当我四处搜索时，我发现 DataContext 对象非常轻量级，我认为这是向每个对象添加 DataContext 实例的好方法。这将减少每次我想更新或删除对象时，再次将分离的对象附加到新的数据上下文实例的需要。
如果您有任何其他解决方案，我将不胜感激。
谢谢
有没有一种简单的方法可以将属性添加到 Linq to Sql 生成的实体以引用其 DataContext？
没有简单的方法可以实现这一点。
请参阅此处：确定 Linq to Sql 查询的源 DataContext
我或多或少地问了同样的问题。您可以从 linq to sql 查询返回的 IQueryable 获取上下文，但据我所知，不能从实体本身获取。
这样做会破坏 LINQ-to-SQL 的部分目的。目的之一是允许您使用您拥有的对象，而不必根据数据库考虑更改您的设计。
在将 DataContext 附加到数据库时，您将代码中的表示与持久化它的方法相结合，这通常是一个糟糕的设计理念。
如果您觉得必须这样做，您始终可以从该类派生，然后在该类上实现一个接口，该接口公开 DataContext。
我建议实现该接口，因为您无法向 LINQ-to-SQL 设计器指示基类，并且您希望所有实体都具有共享实现。
Actually, I agree to casperOne. If you really have to need this, I remembered that the classes that linq-to-sql generates are partial. So you can write a partial class to any class you want and add extended functionalities to it.
这是我为 System.Data.Linq 制作的自定义包装器。它包含一个 find 方法，所以不是你的代码：
var myContext = new DataContext();
var product = context.Products.Where(p => p.Id == productId).SingleOrDefault();
你可以这样做
var myContext = new DataContext();
var product = context.Products.Find(productId); //(assuming productId is your primary key)
您可以获取下面的代码并进行任何您希望设置 product.Context 的自定义修改，但这是修改 DataContext 的示例。
我还做了保存和删除方法。你会注意到我出去重新抓取记录，即使它正在被传递。我这样做是因为记录可能会与上下文分离并且不会更新。如果有人想要完整的代码，我可以发布 github 链接。
public abstract class DbContext : IDisposable
{
#region Properties
private string _connectionString { get; set; }
private DataContext _context { get; set; }
#endregion
#region Constructor
public DbContext(string connectionString)
{
_connectionString = connectionString;
_context = new DataContext(_connectionString);
Initialized(_context);
}
public DbContext(string server, string database, string userID, string password)
{
_connectionString = string.Format(
"Server={0};Database={1};User Id={2};Password={3};MultipleActiveResultSets=true",
server,
database,
userID,
password);
_context = new DataContext(_connectionString);
Initialized(_context);
}
#endregion
#region Methods
/// <summary>
/// Is used to get the contents of a Sql Server Table.
/// </summary>
/// <typeparam name="TEntity">Type</typeparam>
/// <returns>Table</returns>
public Table<TEntity> GetTable<TEntity, TPKType>()
where TEntity : DbTableEquatable<IDbTableEquatable<TPKType>>
where TPKType : struct
{
return _context.GetTable<TEntity>();
}
/// <summary>
/// Is used to get the contents of a Sql Server Table.
/// </summary>
/// <typeparam name="TEntity">Type</typeparam>
/// <returns>Table</returns>
public Table<TEntity> GetTable<TEntity>()
where TEntity : DbTableEquatable<IDbTableEquatable<long>>
{
return GetTable<TEntity, long>();
}
protected virtual void Initialized(DataContext context) { }
/// <summary>
/// Saves the changes to the database. In order to save the table must inherit from DbTableEquatable
/// and be a type of IDbTableEquatable and the Primary Key Type must be a C# Structure
/// </summary>
/// <typeparam name="TEntity">Record Type</typeparam>
/// <typeparam name="TPKType">Primary Key Type</typeparam>
/// <param name="entity">Record</param>
public virtual void SaveChanges<TEntity, TPKType>(TEntity entity)
where TEntity : DbTableEquatable<IDbTableEquatable<TPKType>>
where TPKType : struct
{
var changedList = _context.GetTable<TEntity>();
var ID = entity.GetType().GetProperty("ID").GetValue(entity);
_preprocessSave<TEntity, TPKType>(entity);
// Save changes
if (Convert.ToInt64(ID) == 0)
{
// Insert
// If No ID we need to insert on submit
_context.GetTable<TEntity>().InsertOnSubmit((TEntity)entity);
_context.SubmitChanges();
}
else
{
// Update
var item = changedList.Where(w => w.Equals(entity)).FirstOrDefault();
ReflectionManager.SetValuesWithSkip(entity, item, "ID");
_context.SubmitChanges();
}
Refresh();
}
/// <summary>
/// Saves the changes to the database. In order to save the Table the Record is from must inherit from DbTableEquatable
/// and be a type of IDbTableEquatable and the Primary Key Type must be a C# Structure
/// </summary>
/// <typeparam name="TEntity">Record Type</typeparam>
/// <param name="entity">Record</param>
public virtual void SaveChanges<TEntity>(TEntity entity)
where TEntity : DbTableEquatable<IDbTableEquatable<long>>
{
SaveChanges<TEntity, long>(entity);
}
/// <summary>
/// Saves any non committed changes to the database
/// </summary>
public void SaveChanges()
{
_context.SubmitChanges();
Refresh();
}
/// <summary>
/// Marks the record as delete and will be deleted when saved
/// </summary>
/// <typeparam name="TEntity">Record Type</typeparam>
/// <typeparam name="TPKType">Primary Key Type</typeparam>
/// <param name="entity">Record</param>
public virtual void DeleteOnSave<TEntity, TPKType>(TEntity entity)
where TEntity : DbTableEquatable<IDbTableEquatable<TPKType>>
where TPKType : struct
{
var item = _context.GetTable<TEntity>().Where(w => w.Equals(entity)).FirstOrDefault();
_context.GetTable<TEntity>().DeleteOnSubmit((TEntity)item);
}
/// <summary>
/// Marks the record as delete and will be deleted when saved
/// </summary>
/// <typeparam name="TEntity">Record Type</typeparam>
/// <param name="entity">Record</param>
public virtual void DeleteOnSave<TEntity>(TEntity entity)
where TEntity : DbTableEquatable<IDbTableEquatable<long>>
{
DeleteOnSave<TEntity, long>(entity);
}
protected virtual void _preprocessSave<TEntity, TPKType>(TEntity entity)
where TEntity : DbTableEquatable<IDbTableEquatable<TPKType>>
where TPKType : struct
{
}
protected virtual void _preprocessSave<TEntity>(TEntity entity)
where TEntity : DbTableEquatable<IDbTableEquatable<long>>
{
_preprocessSave<TEntity, long>(entity);
}
public void Dispose()
{
_connectionString = "";
_context.Dispose();
_context = null;
}
public virtual void Refresh<TEntity>(RefreshMode mode, TEntity entity) where TEntity : class
{
_context.Refresh(RefreshMode.OverwriteCurrentValues, entity);
}
public virtual void Refresh()
{
_context = new DataContext(_connectionString);
}
public virtual void Refresh<TEntity>(RefreshMode mode, params TEntity[] entities) where TEntity : class
{
_context.Refresh(RefreshMode.OverwriteCurrentValues, entities);
}
public virtual void Refresh<TEntity>(RefreshMode mode, IEnumerable<TEntity> entities) where TEntity : class
{
_context.Refresh(RefreshMode.OverwriteCurrentValues, entities);
}
#endregion
}
扩展
public static class Extension
{
public static TEntity Find<TEntity, TPKType>(this Table<TEntity> table, TPKType ID, string pkName = "ID")
where TEntity : DbTableEquatable<IDbTableEquatable<TPKType>>
where TPKType : struct
{
TEntity copy = Activator.CreateInstance<TEntity>();
// set value through reflection
copy.GetType().GetProperty(pkName).SetValue(copy, ID, null);
return (TEntity)table.Where(w => w.Equals(copy)).FirstOrDefault();
}
public static TEntity Find<TEntity>(this Table<TEntity> table, long ID, string pkName = "ID")
where TEntity : DbTableEquatable<IDbTableEquatable<long>>
{
TEntity copy = Activator.CreateInstance<TEntity>();
// set value through reflection
copy.GetType().GetProperty(pkName).SetValue(copy, ID, null);
return (TEntity)table.Where(w => w.Equals(copy)).FirstOrDefault();
}
}
}
接口/抽象
/// <summary>
/// This Class Assumes the type T has a property called ID. MUST be
/// used with IDbEquatable
/// </summary>
/// <typeparam name="T">Class Type</typeparam>
public abstract class DbTableEquatable<T> : IEquatable<T> where T : class
{
public bool Equals(T other)
{
//Check whether the compared object is null.
if (Object.ReferenceEquals(other, null))
{
return false;
}
//Check whether the compared object references the same data.
if (Object.ReferenceEquals(this, other))
{
return true;
}
return ((dynamic)other).ID == ((dynamic)this).ID;
}
}
/// <summary>
/// Needs to be inherited from in order for Ion.Data.Linq functions to work
/// </summary>
/// <typeparam name="T">Primary Key Type</typeparam>
public interface IDbTableEquatable<T>
{
T ID { get; set; }
}
这是一个表实现
[Table(Name = "Crews")]
public class Crew : DbTableEquatable<IDbTableEquatable<long>>, IDbTableEquatable<long>
{
[Column(IsPrimaryKey = true, DbType = "Bigint NOT NULL IDENTITY", AutoSync = AutoSync.OnInsert, IsDbGenerated = true)]
public long ID { get; set; }
[Column]
public string Alias { get; set; }
[Column]
public string DefaultForeground { get; set; }
[Column]
public string DefaultBackground { get; set; }
[Column]
public string AccountEmailAddress { get; set; }
[Column]
public long? CrewLeaderEmployeeID { get; set; }
[Column]
public string Comments { get; set; }
[Column]
public string Password { get; set; }
[Column]
public string PrivateICSLink { get; set; }
[Column]
public string PrivateXMLLink { get; set; }
}
将数据上下文作为 ref 参数传递给部分 Product 对象的自定义方法：
public partial class Product
{
public string GetSomethingElse(ref DataContext dbase)
{
return dbase.OtherTableWhatever.Count.ToString(); // whatever
}
}
在你的 aspx.cs 里面：
var context = new DataContext();
var product = context.Products.SingleOrDefault(x => x.id == 1);
var s = product.GetSomethingElse(ref context);