EntityFramework - Partial update of a row in a table?

Question

ASP.NET

Good day.
There is a simple table in the database

CREATE TABLE [dbo].[Users]
(
    [Id] INT NOT NULL PRIMARY KEY, 
    [FirstName] VARCHAR(50) NOT NULL, 
    [LastName] VARCHAR(50) NOT NULL, 
    [Age] INT NOT NULL
)

What is the correct way to write a controller method to update one (or more columns) ?

[HttpPatch]
        public ActionResult Patch([FromBody]User userData)
        {
            var user = Db.Users.FirstOrDefault(entity => entity.Id== userData.Id);
            if (userTokenData == null)
            {
                return null;
            }
 
            user.FirstName = userData.FirstName; // ??
            Db.SaveChanges();
            return Json(user);
        }

To be able to send queries like: Only the Age column should be updated. FirstName and LastName columns should be updated.
{ Id: 1, Age: 42 }
{ Id: 1, FirstName: "Alex", LastName: "Ander" }

Answer 1

_context.Entry(userData).State = EntityState.Modified;
 try
{
    await _context.SaveChangesAsync();
}
catch (DbUpdateConcurrencyException)
{
    if (!Db.Users.Any( a => a.Id==userData.Id))
    {
        return NotFound();
    }
    else
    {
        throw;
    }
}