[英]How can I get around this issue with interfaces?
I am using Entity Framework and that's where my issue is, but it is probably not relevant as I think this is a generic C# question. 我正在使用实体框架,这就是我的问题所在,但它可能不相关,因为我认为这是一个通用的C#问题。
I have a MyContext
class which has many DbSet<T>
properties. 我有一个
MyContext
类,它有许多DbSet<T>
属性。
In order to unit test it, I edited MyContext so these are IDbSet<T>
instead and mock it all up. 为了对它进行单元测试,我编辑了MyContext,所以这些是
IDbSet<T>
而是模拟它。 IDbSet<T>
is part of Entity Framework and DbSet implements it so the two are almost identical. IDbSet<T>
是Entity Framework的一部分,DbSet实现它,因此两者几乎完全相同。
Everything works great like this, because I can do to IDbSet<T>
everything I could do to DbSet<T>
一切都很像这样,因为我可以做
IDbSet<T>
我可以对DbSet<T>
做的一切
Everything except for one thing - DbSet
has a method called SqlQuery(..)
that I also want to be able to call from my IDbSet
. 除了一件事之外的一切
DbSet
有一个叫做SqlQuery(..)
的方法,我也希望能够从我的IDbSet
调用IDbSet
。
Since I can't alter DbSet
or IDbSet
, this leaves me with a conundrum. 由于我不能改变
DbSet
或IDbSet
,这给我留下了一个难题。 I can't get my head around exactly how I can make it so my IDbSet
is able to have a SearchQuery(..)
method added to it in some logical fashion. 我无法理解我是如何做到这一点所以我的
IDbSet
能够以某种逻辑方式添加一个SearchQuery(..)
方法。
Does that make sense? 那有意义吗? I'm quite confused so I may have overlooked something really simple, such as copy & pasting
IDbSet
and renaming it and adding SearchQuery()
. 我很困惑所以我可能忽略了一些非常简单的东西,比如复制和粘贴
IDbSet
并重命名它并添加SearchQuery()
。 Any ideas? 有任何想法吗?
EDIT 编辑
I believe I got what you're looking for - wrappers everywhere, possibly more trouble than it's worth, but worth a look: 我相信我得到了你想要的东西 - 到处都是包装纸,可能比它的价值更麻烦,但值得一看:
// An interface which implements IDbSet<T> and adds on the method you want
public interface IExtendedDbSet<T> : IDbSet<T>
where T : class
{
DbSqlQuery<T> SqlQuery(string sql, object[] parameters);
}
// Implement this interface by wrapping around a regular DbSet<T>.
// You implement all the methods and properties by just wrapping the DbSet<T>
// calls
public class ExtendedDbSet<T> : IExtendedDbSet<T>
where T : class
{
private readonly DbSet<T> _dbSet;
public ExtendedDbSet(DbSet<T> dbSet) { _dbSet = dbSet; }
DbSqlQuery<T> IExtendedDbSet<T>.SqlQuery(string sql, object[] parameters)
{
return _dbSet.SqlQuery(sql, parameters);
}
T IDbSet<T>.Add(T entity) { return _dbSet.Add(entity); }
T IDbSet<T>.Attach(T entity) { return _dbSet.Attach(entity); }
TDerivedEntity IDbSet<T>.Create<TDerivedEntity>() { return _dbSet.Create<TDerivedEntity>(); }
T IDbSet<T>.Create() { return _dbSet.Create(); }
T IDbSet<T>.Find(params object[] keyValues) { return _dbSet.Find(keyValues); }
ObservableCollection<T> IDbSet<T>.Local { get { return _dbSet.Local; } }
T IDbSet<T>.Remove(T entity) { return _dbSet.Remove(entity); }
IEnumerator<T> IEnumerable<T>.GetEnumerator() { return ((IEnumerable<T>)_dbSet).GetEnumerator(); }
IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable)_dbSet).GetEnumerator(); }
Type IQueryable.ElementType { get { return ((IQueryable)_dbSet).ElementType; } }
Expression IQueryable.Expression { get { return ((IQueryable)_dbSet).Expression; } }
IQueryProvider IQueryable.Provider { get { return ((IQueryable)_dbSet).Provider; } }
}
// A regular context class, no special interfaces to implement or
// custom properties or anything.
public class MyContext : DbContext
{
public DbSet<Car> Cars { get; set; }
}
// An interface representing your context, which exposes extended DbSet<T>
// for your sets. Also define SaveChanges() and whatever else you may need
// to call on your context object.
public interface IMyContext
: IDisposable
{
IExtendedDbSet<Car> Cars { get; }
int SaveChanges();
}
// A wrapper around your regular context. For each set, return an
// ExtendedDbSet<T> wrapper.
public class MyContextWrapper : IMyContext
{
private readonly MyContext _myContext;
public MyContextWrapper(MyContext myContext) { _myContext = myContext; }
IExtendedDbSet<Car> IMyContext.Cars
{
get { return new ExtendedDbSet<Car>(_myContext.Cars); }
}
void IDisposable.Dispose()
{
_myContext.Dispose();
}
int IMyContext.SaveChanges()
{
return _myContext.SaveChanges();
}
}
// Define your context variable as IMyContext, and create it
// by creating a wrapper around a regular context. The properties
// of the interface will be extended wrappers around your sets.
internal class Program
{
private static void Main(string[] args)
{
using (IMyContext context = new MyContextWrapper(new MyContext()))
{
Console.WriteLine(context.Cars.SqlQuery("select 1", new object[0]));
}
}
}
Hmm, it may not be the most elegant solution, but you could simply write an extension method like this: 嗯,它可能不是最优雅的解决方案,但您可以简单地编写这样的扩展方法:
public IEnumerable<T> SearchQuery(this IDbSet<T> set, string query)
{
var dbSet = set as DbSet<T>;
if (dbSet != null)
{
return dbSet.SqlQuery(query);
}
else
{
throw new NotSupportedException();
}
}
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