Question

Newbie to LINQ, and trying to write the following query…

select    f.Section_ID,    f.Page_ID,    f.SortOrder,    f.Type from  (   select      Section_ID,      min(SortOrder) as minSortOrder   from      ContentPages    group by      Section_ID ) as x  inner join    ContentPages as f on      f.Section_ID = x.Section_ID and      f.SortOrder = x.minSortOrder; 

Notes:

• ‘Section’ has many ‘ContentPages’
• Sections are ordered by a ‘SortOrder’ field
• ContentPages are also ordered by a ‘SortOrder’ field

Table: Section
Section_ID….Name…….SortOrder
….1………One……….1……
….2………Two……….3……
….3………Three……..2……

Table: ContentPage
Page_ID…….Section_ID…….Title…………..SortOrder
….11………….1………. Page One………….1……
….12………….1………..Page Two………….3……
….13………….2………..Page Three………..2……
….16………….2………. Page Four…………4……
….17………….2………..Page Eight………..5……
….18………….1………..Page Ten………….6……

The above query could possibly be written another way, so here’s what I’m trying to do:

• I need to return a list of the first ContentPage within each Section (when sorted by ContentPage.SortOrder)
• Sort results by Section.SortOrder
• Show Section.Name (join on Section_ID?) in the result as well

Last 2 points are not covered by the sql query above and are more of a ‘nice to have’…

Desired Result
Page_ID…….Section_ID…SectionName…..Title…………..SortOrder
….11………….1………One……… Page One………….1……
….13………….2………Two……….Page Three………..2……

Any help is appreciated. Thanks!

Answer 1

Here’s my first attempt at it:

from sectionPage in pages group sectionPage by sectionPage.Section_ID into sectionGroup join page in pages on sectionGroup.Key equals page.Section_ID where page.SortOrder == sectionGroup.Min(p => p.SortOrder) orderby page.SortOrder select page; 

What happens is first we create a group on the section id so that we can get the minimum sort order later. Next, we join a new reference to pages in on the section id, and filter by SortOrder being the minimum from the section group. Note, for simple expressions like the Min() call, I prefer the inline lambda expression over another query.

Finally, we add an orderby to order the pages, and we return the page (note you can change this to certain fields if you prefer).