Merging Multiple related Queries in .Net Core

Question

I want to implement a Page where each Category have its related articles, I have implemented it as follow:

  ArticlesHomeViewModel articles  = new ArticlesHomeViewModel
  { 
    category1 = db.Articles.Include(o => o.Category).Where(m => m.category == "Category One Name").limit(4),
    category2 = db.Articles.Include(o => o.Category).Where(m => m.category == "Category two Name").limit(4),
    category3 = db.Articles.Include(o => o.Category).Where(m => m.category == "Category Three Name").limit(4),
    category4 = db.Articles.Include(o => o.Category).Where(m => m.category == "Category Four Name").limit(4),
  }

And I want to merge them into one query to be able to loop against them in the view because I don't know how many categories that could be in the system.

Since you do not know how many categories. I think you should use a `GroupBy` query -> https://stackoverflow.com/questions/7325278/group-by-in-linq — panoskarajohn, Dec 22 '19 at 10:30
Please also take a look at my edit you have syntactical errors. — panoskarajohn, Dec 22 '19 at 11:18

score 0 · Accepted Answer · answered Dec 22 '19 at 10:32

Define a category array.

var categories = new[]{"Category One Name","Category Two Name",
                       "Category Three Name","Category Four Name"};

Then

// Include is redundant
var result = db.Articles.Where(art=> categories.Contains(art.Category.Name)) 
            .GroupBy(art=>art.CateGory.Name) // use group for feature uses
            .SelectMany(grouped=>// use selectmany to select individual items
                grouped.OrderBy(t=>t.Id).Take(4))  // and apply paging in group
            .ToArray();

Merging Multiple related Queries in .Net Core

1 Answers1