mvc: same query for different repositories? - repository-pattern

Question

My friends, you always help me in any bad situations :) Thank you.
I have 2 or more repositories working in their own contexts which return data joining to the same base query:
public IQueryable<LQ_Group> GetAdminedGroupsQ(User user)
{
try
{
return
(from ap in context.LQ_Permissions
join g in context.LQ_Groups on
new { GroupID = ap.ObjectID, GroupTypeID = ap.ObjectTypeID }
equals
new { GroupID = g.GroupID, GroupTypeID = Dict.ObjectType[ObjectType.Group].ID }
where ((ap.SubjectID == user.ID) && (ap.SubjectTypeID == Dict.ObjectType[ObjectType.User].ID))
select g);
}
catch (Exception ex)
{
throw new UnknownRepositoryException(ex.Message);
}
}
This result is used by User, Group, GroupMember and others reposotories.
What is the best way to implement that? I dont like idea to have different copies of the same logic. Thoughts?
Thank you.

Answer 1

You could do something like this:
public class MyRepository
{
private List<Item> mItems;
public IEnumerable<Item> GetAllItems()
{
return this.mItems;
}
public IEnumerable<Item> GetGoodItems()
{
return this.GetAllItems().Where(x => x.IsGood == true);
}
public IEnumerable<Item> GetGoodItemsOverFiveDollars()
{
return this.GetGoodItems().Where(x => x.Price > 5.00m);
}
}
public class Item
{
public bool IsGood { get; set; }
public decimal Price { get; set; }
}
You can do this because the query is not executed until the enumeration is evaluated. However, keep in mind that additional linq statements can be added outside the MyRepository class, and thus you can have "linq injection" ;).
You could avoid this by wrapping the methods and making them internal, where your wrapping methods call ToList or ToArray, allowing the query to execute.
How are you currently executing your queries, and what repetition are you trying to reduce? Can you provide an example?