my API

        [HttpPost("AffectationRoleToUser")]
        public async Task<IActionResult> AssignRoleToUser(int userId, int roleId)
        {
            try
            {
                var user = await _context.Users.FindAsync(userId);
                var role = await _context.Roles.FindAsync(roleId);

                if (user == null)
                    return NotFound(new { Message = "User not found!" });

                if (role == null)
                    return NotFound(new { Message = "Role not found!" });

                var affectationRole = new AffectationRole
                {
                    User = user,
                    Role = role,
                    DateAffectation = DateTime.Now
                };

                _context.AffectationRoles.Add(affectationRole);
                await _context.SaveChangesAsync();

                return Ok(new { Message = "Role assigned to user successfully!" });
            }
            catch (Exception ex)
            {
                // Log the exception
                Console.WriteLine($"An error occurred while assigning role to user: {ex.Message}");
                return StatusCode(500, new { Message = "An error occurred while assigning role to user. Please try again later." });
            }
        }

and this is my page, my question is, how to or what logic can I use to assign these roles to all these users at once.
(https://i.stack.imgur.com/kHO4I.png)

i’ve tried to store the ID of the user and the ID of the role in a list then send them but it didn’t work