我怎样才能使这个 LINQ 到 SQL where 条件更快？

Question

I have the following LINQ to SQL query but I want to know if there is a faster way to validate data from a post action before adding them in a where clause? ex:

bookFilter = Informations coming from the post action

int count = from b in _libraryContext.Book
            join ba in _libraryContext.BookAuthor
            on b.Id equals ba.BookId
            where (!string.IsNullOrWhiteSpace(bookFilter.Name) ? 
            b.Name.Contains(bookFilter.Name.ToUpper()) : 1 == 1 )
            where (!string.IsNullOrWhiteSpace(bookFilter.Decription) ? 
            b.Description.Contains(bookFilter.Description.ToUpper()) : 1 == 1)
            where (bookFilter.BookId > 0 ? ba.BookId == bookFilter.BookId : 1 == 1)

return count;

Answer 1

I've never used this type of syntax much so I'm sure if you can do it this way, but you can certainly do it with LINQ and build up your query step by step like so:

var query = _libraryContext.Set<Book>();

if(!string.IsNullOrWhiteSpace(bookFilter.Name))
{
    query = query.Where(x => x.Name.Contains(bookFilter.Name.ToUpper()));
}

if(!string.IsNullOrWhiteSpace(bookFilter.Description))
{
    query = query.Where(x => x.Description.Contains(bookFilter.Description.ToUpper()));
}

if(bookFilter.BookId > 0)
{
    query = query.Where(x => x.BookId == bookFilter.Id);
}

return query.Count();

Note: I have omitted the JOIN here as it seems unnecessary, but you can of course do the join in this syntax too if you need it.

Answer 2

You have accepted the solution that @Akinzekeel provided above. However, in the case that you are trying to use a single LINQ query, I would go for the solution below:

bookFilter = Informations coming from the post action

Please note here bookFilter has to be IQueryable!

int count = from b in _libraryContext.Book
            join ba in _libraryContext.BookAuthor
            on b.Id equals ba.BookId
            where (b.Name.Contains(bookFilter.Name.ToUpper()) || string.IsNullOrWhiteSpace(bookFilter.Name)) && 
            (b.Description.Contains(bookFilter.Description.ToUpper()) || string.IsNullOrWhiteSpace(bookFilter.Decription)) &&
            (ba.BookId == bookFilter.BookId || bookFilter.BookId == 0 )

return count;

If you trace the code above in SQL Profiler, you will see this will generate a single SQL query; something like (OR IS NULL) conditions.

Answer 3

In SQL you could use COALESCE to default ignore parameters -- like the following:

SELECT *
FROM book b
JOIN BookAuthor ba on b.id = ba.Bookid
WHERE COALESCE(UPPER(name), UPPER(b.name)) = UPPER(b.name)
  AND COALESCE(UPPER(description), UPPER(b.description)) = UPPER(b.description)
  AND COALESCE(bookid, b.book.id) = b.bookid 

Recommended pattern is to put something like that in a SP and then call the SP.