Don't include .Where() if variable is null ASP.NET MVC-CodePudding

I have this function:

        public List<PostIndexResponse> GetPosts(string search, int? categoryId)
        {
            var currentUserId = HttpContext.Current.User.Identity.GetUserId() ?? "";
            var srch = search ?? "";
            var posts = _set.Where(x => x.PersonId.Contains(currentUserId) && x.Description.Contains(srch) && x.CategoryId == categoryId).OrderByDescending(x => x.CreatedOn)).ToList();
            return posts;
        }

I want to have x.CategoryId == categoryId only if categoryId is not null. How do I do this without having an if else condition and creating another query based if it is null or not?

CodePudding user response：

I would break it up in to a couple lines something like this (UNTESTED)...

This allows you to conditionally filter on categoryId and I think it's cleaner and more maintainable than attempting to cram it all in to a single expression. No need to create 2 overlapping expressions

public List<PostIndexResponse> GetPosts(string search, int? categoryId)
{
    var currentUserId = HttpContext.Current.User.Identity.GetUserId() ?? "";
    var srch = search ?? "";

    var query = _set.Where(x => x.PersonId.Contains(currentUserId) && x.Description.Contains(srch));

    if (categoryId.HasValue)
        query = query.Where(x => x.CategoryId == categoryId);

    var posts = query.OrderByDescending(x => x.CreatedOn)).ToList();
    return posts;
}

The other option is to replace x.CategoryId == categoryId with

(categoryId == null || x.CategoryId == categoryId)

But that expression is already getting long and difficult to maintain.