entity-framework-6 - 动态添加多个包含

Question

我整理了一些帮助程序，允许我按类型注册包含内容。看起来像这样:

Dictionary<Type, LambdaExpression[]> includes = 
    new Dictionary<Type, LambdaExpression[]>();

我注册的内容如下:

public void Add<T>(params Expression<Func<T, object>>[] includes)
{
    this.includes.Add(typeof(T), includes);
}

Add<Customer>(e => 
    e.Address.City.Province.Country,
    e.Products.Select(p => p.Category));

请注意，客户有两个包含项。然后我有一个按类型包含的方法:

DbSet<T> entitySet = null;

void LoadIncludes()
{
    var includes = Includes.Instance.Get<T>().DirectCast<Expression<Func<T, object>>[]>();

    if (includes != null)
    {
        foreach (var include in includes)
        {
            entitySet.Include(include).Load();
        }
    }
}

获取我的实体时，我这样做:

public T GetById(int id)
{
    LoadIncludes();

    return entitySet.SingleOrDefault(x => x.Id == id);
}

它工作得很好，但是太慢了，这是因为我在 LoadIncludes() 中调用了 .Load() 方法。有没有更快的方法来完成我想做的事情？

Answer 1

您不应该调用Load ，但构建并使用 Queryable<T>与 Include链。

替换LoadIncludes具有私有(private)功能:

private IQueryable<T> GetEntitySet()
{
    var set = entitySet.AsQueryable();
    var includes = Includes.Instance.Get<T>().DirectCast<Expression<Func<T, object>>[]>();
    if (includes != null)
    {
        foreach (var include in includes)
        {
            set = set.Include(include);
        }
    }
    return set;
}

并按如下方式使用它:

public T GetById(int id)
{
    return GetEntitySet().SingleOrDefault(x => x.Id == id);
}