Question

I didn’t plan project correctly from beginning so I ended up having many SQL Queries scatterd around page.

So to avoid catching Sql exceptions in every other method or missing half of page due to exception in one of methods I want to pull all the data I need so :

This is method from dll file, I need to return it so I can work with objects after context dispose but I am doing something awfully wrong (first query finalproduct returns empty):

 public static Tuple<Product, IEnumerable<Tag>, IEnumerable<ProductComment>, IEnumerable<ProductVote>, IEnumerable<Review>, IEnumerable<ReviewComment>, IEnumerable<ReviewVote>> GetBigProduct(int productID)    
            {
                using (ProductClassesDataContext context = new ProductClassesDataContext())
                {
                    var outproduct = from product in context.Products
                                     where product.ID == productID
                                     join producttag in context.ProductTags on product.ID equals producttag.productID
                                     join tag in context.Tags on producttag.TagID equals tag.ID
                                     join productComment in context.ProductComments on product.ID equals productComment.productID
                                     join productVote in context.ProductVotes on product.ID equals productVote.productID
                                     join review in context.Reviews on product.ID equals review.productID
                                     join reviewComment in context.ReviewComments on review.ID equals reviewComment.reviewID
                                     join reviewVote in context.ReviewVotes on review.ID equals reviewVote.reviewID
                                     select new Tuple<Product, Tag, ProductComment, ProductVote, Review, ReviewComment, ReviewVote>
                                                     (product, tag, productComment, productVote, review, reviewComment, reviewVote);


                    var finalProduct = (from t in outproduct select t.Item1).Single();

                    var finalTags = (from t in outproduct select t.Item2).ToList();

                    var finalProductComments = (from t in outproduct select t.Item3).ToList();

                    var finalProductVotes = (from t in outproduct select t.Item4).ToList();

                    var finalReviews = (from t in outproduct select t.Item5).ToList();

                    var finalReviewsComments = (from t in outproduct select t.Item6).ToList();

                    var finalReviewsVotes = (from t in outproduct select t.Item7).ToList();

                    return new Tuple<Product, IEnumerable<Tag>, IEnumerable<ProductComment>, IEnumerable<ProductVote>, IEnumerable<Review>, IEnumerable<ReviewComment>, IEnumerable<ReviewVote>>
                               (finalProduct, finalTags, finalProductComments, finalProductVotes, finalReviews, finalReviewsComments, finalReviewsVotes);
                }
            }

Answer 1

Are you sure there is only one element returned by from t in outproduct select t.Item1 query?
According to documentation, Single():

Returns the only element of a sequence, and throws an exception if
there is not exactly one element in the sequence.

You may need First() or FirstOrDefault() instead.

Update after comments

I think the problem is with your joins. Actually, I don’t think you want to do joins here. What you need, I guess, is something like following:

var outproduct = from product in context.Products
                 where product.ID == productID
                 select new Tuple<Product, ProductComment, Tag>(
                      product, // product itself
                      context.ProductComments.Where(p => p.productID == product.ID).ToList(), // list of comments for this product
                      (from pt in context.ProductTags
                      join tag in context.Tags on pt.TagID equals tag.ID
                      where pt.productID = product.ID
                      select tag).ToList() // list of tags for this product
                      // ... more dimensions in tuple
                 );

Then you will get, out of outproduct query, a collection of of tuples containing <Product, List of ProductComments, List of Tags>.
You can easily add rest of your tuple dimensions. I removed them for simplicity.

You can now returns this tuple directly from your function doing just

return outproduct.FirstOfDefault()

There is no need for your var finalProduct =-style lines and rebuilding the final tuple.