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How would you implement pagination when the input data needs to be grouped first? I understand how to implement pagination from the link below:

LINQ and pagination

, but I would like to be able to do this where each item in the paginated list is a group (that can be expanded) from the input data. Something similar to the code below - to prevent retrieving all rows of the table into memory, ordersList is IQueryable. The IQueryable returned is what I would like to pass into the pagination function.

from order in ordersList
group order by order.FullName into customers
select customers

However, a query like this runs on the client (and actually throws an exception in Entity Framework Core 3.0+). Is there a way to only retrieve the items on the current page for this situation?

LivingAntelope
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2 Answers2

2

You have to retrieve limited data and then group on the client side:

var keys = ordersList
   .Select(o => new {o.FullName})
   .Distinct()
   .OrderBy(ะพ => o.FullName)
   .Skip(pageNumber * pageSize)
   .Take(pageSize);

var items =
   from order in ordersList
   join key in keys on order.FullName equals key.FullName
   select order;

var result = 
   from order in items.AsEnumerable()
   group order by order.FullName into customers
   select customers;
Svyatoslav Danyliv
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1

You must paginate by group. You should use the group number instead of the page number.

//group sequence
int groupSeq = 1;

//select current group
var p = (from order in context.TBLGroups
       group order by order.FullName into customers
       select customers.Key).OrderBy(a => a).Skip(groupSeq - 1).Take(1).FirstOrDefault();
       string FullName = p.ToString();

//get all items in current group
var items = (from order in context.TBLGroups
       where order.FullName == FullName
       select order).ToList();
Meysam Asadi
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