Question

I’m learning Linq-to-Sql, and I’m encountering the scenario where I’m trying to build a dynamic query with sorting, filtering, and paging.

If I run a query like this I am able to get “paged” results:

IQueryable<WorkOrder> query = (_dataContext.WorkOrders).Skip((search.page - 1) * search.rows).Take(search.rows);
var retval = query.ToList();

in this case the generated query looks like this:

SELECT <columns>
FROM (
    SELECT ROW_NUMBER() OVER (<columns>) AS [ROW_NUMBER], <columns>
    FROM [dbo].[WorkOrders] AS [t0]
    ) AS [t1]
WHERE [t1].[ROW_NUMBER] BETWEEN @p0 + 1 AND @p0 + @p1
ORDER BY [t1].[ROW_NUMBER]

However if I run the query like this, it is no longer paged:

IQueryable<WorkOrder> query = (_dataContext.WorkOrders);
query.Skip((search.page - 1) * search.rows).Take(search.rows);
var retval = query.ToList();

In this case, the generated query looks like this:

SELECT <cut for brevity>
FROM [dbo].[WorkOrders] AS [t0]

I can’t really grok what is going here… exactly when does Linq to Sql generate the query, and is it possible to add extra criteria like Skip, Take, OrderBy to an existing IQueryable? Where I’d like to end up would be something like this:

IQueryable<WorkOrder> query = (_dataContext.WorkOrders);
if (User.IsNotAuthorizedToSeeSomething) {
    query.Where(...);
}
if (search.sortField.Equals("Name")) {
    query.OrderBy(...);
}
query.Skip((search.page - 1) * search.rows).Take(search.rows);
var retval = query.ToList();

Answer 1

Instead of

IQueryable<WorkOrder> query = (_dataContext.WorkOrders);
query.Skip((search.page - 1) * search.rows).Take(search.rows);
var retval = query.ToList();

try

IQueryable<WorkOrder> query = (_dataContext.WorkOrders);
query = query.Skip((search.page - 1) * search.rows).Take(search.rows);
var retval = query.ToList();

each query.Xxx() is not applying Xxx on query object but returns new object.