添加到LINQ包含表达式

Question

我正在编写一个函数，允许用户从数据库(底层提供程序是EF)获得可查询的设备列表。但我希望允许它们指定自己的包含，但如果它们总是包含Capabilites的默认包含，我该怎么做呢?

public IQueryable<Device> GetAllDevices(params Expression<Func<Device, object>>[] includes)
{
    // I really want to do something like includes.Add(d => d.Capabilities)
    // (I know the above code wouldnt work, but illustrates what I want)
    var newIncludes = includes /*(and somehow)*/ d => d.Capabilities, 
    return this.Repository.GetAll(newIncludes);
}

这是在我的存储库类上使用的函数，它聚合了在其中发送的包含。我似乎不知道如何在上面的函数

中添加一个默认的include。

public IQueryable<T> GetAll(params Expression<Func<T, object>>[] includes)
{
    IQueryable<T> query = this.dbset;
    if (includes != null)
    {
        query = includes.Aggregate(query, (current, include) => current.Include(include));
    }
    return query;
}

Answer 1

不使用相同的Include()两次没有特定的限制。第二个被忽略。

public IQueryable<Device> GetAllDevices(params Expression<Func<Device, object>>[] includes)
{
    return this.Repository.GetAll(includes).Include(x => x.Capabilities);
}

这将始终是Include(x => x.Capabilities)。

你的问题不清楚……也许如果用户不包含任何内容(includes为空)，则不希望包含Capabilities:

public IQueryable<Device> GetAllDevices(params Expression<Func<Device, object>>[] includes)
{
    IQueryable<Device> query = this.Repository.GetAll(includes);
    if (includes != null && includes.Length != 0)
    {
        query = query.Include(x => x.Capabilities);
    }
    return query;
}

Answer 2

你可以链"包括()其中包括()……":

(IQueryable<T>).Include("Something").Include("SomethingElse");

你可以使用它，并在"includes"数组上循环，这样就可以实现你的函数:

IQueryable<T> example = (some IQueryable<T>).Include(Capabilities);
foreach (include in includes)
    example.Include(include);

Answer 3

返回DbSet其中(你的情况)其中包括(string.Join("。",包括)).FirstOrDefault ();