Question

目前我有一个函数允许我查询数据库，同时在结果中包含一些其他相关表，以防止返回数据库，如果我不知道会发生这种情况：

public class EntityRepository<TEntity> : IEntityRepository<TEntity> where TEntity : class
{
    protected DbSet<TEntity> dbSet;

    private readonly DbContext dc;

    public EntityRepository()
    {
        dc = new DbContext(Utility.Config.GetEntityDbConnection());
        dbSet = dc.Set<TEntity>();
    }


    public IQueryable<TEntity> GetAllIncluding(params Expression<Func<TEntity, object>>[] includeProperties)
    {
            foreach (var includedProperty in includeProperties)
            {
                dbSet.Include(includedProperty).Load();
            }

            return dbSet;
    }
}

但是，我还需要在include之前使用where子句，以便在触发Load()方法时不会尝试查询整个数据库。

我试图做这样的事情（这显然不起作用，因为你可以在下面的示例代码中重新分配dbset。）

    public IQueryable<TEntity> SearchForIncluding(Expression<Func<TEntity, bool>> predicate, params Expression<Func<TEntity, object>>[] includeProperties)
    {
           dbset = dbSet.Where(predicate);  //THIS DOESN'T WORK OBVIOUSLY

           foreach (var includedProperty in includeProperties)
           {
                dbSet.Include(includedProperty).Load();
           }
    }

Answer 1

您应该能够在Where和Include之间的Load调用中应用谓词，如下所示：

foreach (var includedProperty in includeProperties)
{
     dbSet.Include(includedProperty).Where(predicate).Load();
}

Answer 2

您可以使用LinqKit库。下载nuget package并使用AsExpandable扩展程序方法：

public IQueryable<TEntity> SearchForIncluding(Expression<Func<TEntity, bool>> predicate, params Expression<Func<TEntity, object>>[] includeProperties)
{
        IQueryable<TEntity> query = dbSet;

        if (includeProperties != null)
        {
            query = includeProperties.Aggregate(query, (current, include) => current.Include(include));
        }
        if (predicate != null)
        {
            query = query.AsExpandable().Where(predicate);
        }
        return query;
}

如何包含谓词和包含的属性？

2 个答案: