c# mongodb find all document with a give item of a list. Otherwise return all documents

Question

The requirements is "Find all the posts with the given tag if it exists. Otherwise, return all the posts". And I try the following

[HttpGet]
public async Task<ActionResult> Posts(string tag = null)
{
    var blogContext = new BlogContext();
    var posts = await blogContext.Posts.Find(Builders<Post>.Filter.AnyEq(x => x.Tags, tag)   )
                     .Sort(Builders<Post>.Sort.Descending("CreatedAtUtc")).ToListAsync();

    return View(posts);
}

My question is how to retrieve all documents when it is not match? thanks,

Answer 1

我知道了。

    var posts = await blogContext.Posts.Find(x => (string.IsNullOrEmpty(tag) || x.Tags.Contains(tag))).Sort(Builders<Post>.Sort.Descending("CreatedAtUtc")).ToListAsync();