ASP.NET Core Web API using Entity Framework Core

Question

How can I post a request to a table generated from joining two tables in Web API, and return only required columns?

This is the code for that:

    public IActionResult GetAll()
    {
        try
        {
            var clients = _db.Clients
                             .Include(cl => cl.Projects)
                             .ToList();

            return Ok(clients);
        }
        catch(Exception ex) 
        {
            throw;
        }
    }