LINQ to SQL Every Nth Row From Table

Question

Anybody know how to write a LINQ to SQL statement to return every nth row from a table? I\'m needing to get the title of the item at the top of each page in a paged data gr

Answer 1

This will do the trick, but it isn't the most efficient query in the world:

var count = query.Count();
var pageSize = 10;
var pageTops = query.Take(1);
for(int i = pageSize; i < count; i += pageSize)
{
    pageTops = pageTops.Concat(query.Skip(i - (i % pageSize)).Take(1));
}
return pageTops;

It dynamically constructs a query to pull the (nth, 2*nth, 3*nth, etc) value from the given query. If you use this technique, you'll probably want to create a limit of maybe ten or twenty names, similar to how Google results page (1-10, and Next), in order to avoid getting an expression so large the database refuses to attempt to parse it.

If you need better performance, you'll probably have to use a stored procedure or a view to represent your query, and include the row number as part of the stored proc results or the view's fields.