How to sort a List with LINQ using Nested Property-CodePudding

I have a Json file with following data:

[ 
   { "Id": 510, "Title": "Big Start", "Author": [{ "AuthId": 7777, "Name": "Tom" }] },
   { "Id": 511, "Title": "Rising Tide", "Author": [{ "AuthId": 6666, "Name": "Bob" }] }
]

For the above, I have defined the following classes:

public class Book {
  public int Id { get; set; }
  public string Title { get; set; }
  public List<Author> Authors { get; set; }
 }
    
 public class Author {
  public int AuthId { get; set; }
  public string Name { get; set; }
 }

I have deserialized the json data using the following code:

List<Book> books;
 using (StreamReader sr = new StreamReader(Server.MapPath("...")))
 {
  books = JsonConvert.DeserializeObject<List<Item>>(sr.ReadToEnd()).ToList()
 }

Now I want to sort the list of books using author Name. I have tried the following:

var list = books.OrderBy(b => b.Author.OrderBy(a => a.Name)).ToList();

But I get the error message 'At least one object must implement IComparable'.

Can someone help me sort the above list using the nested author Name.

Thanks in advance.

CodePudding user response：

Thing is, Authors is a List, so which author name do we sort by? There might be many. "Book1, by Alfred and Zeus", "Book2 by Zigo, Mary and Ada" - how do these books sort? How do they sort if Book2 was by Ada, Mary and Zigo?

If there's only ever one author it's fairly simple

var list = books.OrderBy(b => b.Authors.First().Name).ToList();

As authors is a list you could also index it

var list = books.OrderBy(b => b.Authors[0].Name).ToList();

If there is ever more than one author you need to have a think about which author is used for sort.. If multiple authors contribute as tie breakers it gets more complex.. You could end up with a ThenBy that skips the first author etc, but then you need to consider if you're going to sort the authors too..

Remember that c# is case sens, so "bob" will sort after "Tom" and also the code above won't work if here are zero authors - you've implied there will always be one but if not, consider FirstOrDefault()?.Name??"" ..

..sometimes the simplest of questions leads to the most involved set of work! ;)